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Thesis/Dissertation Announcements

Thesis/Dissertation Announcements

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Fall 2016

Thesis Defense

“Optic Nerve of Zebrafish (Danio rerio) as a Model for Aging Studies in Humans”

Name: Pedro Gonzalez Jr.

Major Advisor: Dr. Dana M. García

Committee Members: Dr. Shannon Weigum, Dr. Joseph Koke  

Monday, November 7, 2016, 3:00 PM, Norris Conference Room

The optic nerve is the cranial nerve that sends messages from the eyes to the brain and is part of the central nervous system (CNS). Astrocytes help maintain neuronal health within the CNS. In humans, senescence of astrocytes is thought to be a factor in aging related diseases. Astrocytes uniquely express glial fibrillary acidic protein (GFAP), a type of intermediate filament. High levels of expression of GFAP are one indicator of reactive astrocytosis. Since increased expression of GFAP is a characteristic response to injury or disease, we hypothesize that increased expression of GFAP in the optic nerve of zebrafish correlates with aging of zebrafish We also investigated p16-ARC, a protein that has been associated with aging-related diseases. Lastly, studies on the changes in the optic nerve of human cadavers in which measurements of the optic nerve were done revealed that there was an increase in the diameter with increasing age. We performed similar measurements on the optic nerve of the zebrafish. If all three of these indicators for aging and senescence are observed, then zebrafish may be a tenable animal model for understanding aging in humans.

The fish were raised in aquaria located in Room 272 of the Supple Science Building or purchased from ZIRC to ensure the exact age of the fish. Fish were euthanized, fixed and dissected. The tissue was be frozen, embedded and sectioned into 20 mm thick sections using a cryotome and then adhered to gelatin-coated coverslips. Antibodies for immunolabeling Gfap were anti-GFAP (zrf-1) raised in mouse (1:200 dilution) as the primary antibody and goat anti-mouse Alexa Fluor 488 (1:300 dilution) as the secondary antibody. The same protocol was used for immunolabeling p16-ARC, but with the addition of anti-p16 antibody and the appropriate secondary antibody. Tissue sections were observed and positive and negative control images were acquired using an Olympus FV1000 confocal laser-scanning microscope. Intensity of labeling was quantified by measuring the pixel intensity using ImageJ software. Optic nerve diameters were measured from images obtained from 6 (n = 5), 9 (n = 5) and 12 (n = 3) month old fish.  Outliers were removed. Data were analyzed using ANOVA and post-hoc t-tests. Contrary to expectations, GFAP labeling was observed in zebrafish as young as 3 months old.  Intensity and extent of labeling increased as fish aged.  Labeling of p16-ARC was observed in 9 and 12 month old fish, but not in 3 and 6 month old fish. The diameter of the optic nerve increased significantly as the fish aged. Overall, our study may support zebrafish as a model organism for better understanding aging in humans.

Bio: Pedro Gonzalez, Jr. obtained a BS in Biology (2014) from St. Mary’s University in San Antonio, Texas. Upon deciding that he wanted to complete a Master’s degree, he entered the MS Biology program in Fall 2014 and joined Dr. García’s lab where he became interested in Neurobiology. Pedro aims to pursue a career in the medical field as a PA and return to his hometown (Harlingen, TX) to serve patients in the underserved region of the Rio Grande Valley.

Thesis Defense

“Mechanisms of Escherichia coli and Vibrio cholerae fitness when grown in co-culture”

Name: Candace Longoria

Major Advisor: Dr. Robert JC McLean

Committee Members: Dr. Karl Klose, Dr. Kavita Kakirde  

Thursday, November 3, 2016, 9:30 AM, Norris Room

Vibrio cholerae is a gram negative bacillus that possesses a single flagellum and is commonly known to have two toxigenic strains: serogroups O1 and O139; both are causes of epidemics. V. cholerae normally lives in brackish aquatic environments that have varying conditions that include temperature, salinity, and pH. Escherichia coli is normally found in the intestinal tract and E. coli K-12 is a commensal non-virulent strain used in many laboratory settings. E. coli and V. cholerae were observed in planktonic and biofilm mixed cultures and V. cholerae was seen to have a reduced fitness in the biofilm environment. To test which E. coli genes are essential for growth with V. cholerae, we used the E. coli KEIO knockout collection of specific K-12 genes and tested the ability of various knockouts to grow with V. cholerae. Once the initial screening was complete we saw the deletion of peptidase activity, most so with pepA-, had visible changes in fitness and growth in both planktonic and biofilm mixed culture. We also used various pepA- strains and plasmids with altered DNA-binding and peptidase activity and observed the growth in mixed culture over a forty-eight hour period. Based on our data, biofilm mixed culture and the lack of peptidase activity may affect the growth and fitness of both E. coli and V. cholerae

Bio: Candace Longoria spent two years at the University of North Texas on a FOCUS scholarship before transferring to the University of Texas at Austin and graduating with her BS in Biology with a focus in Evolution, Ecology, and Behavior and a Minor in Chemistry. After a year in the real world, she entered the MS Biology program in the Fall of 2014 in hopes of providing a better future for her dog, Pig

Thesis Defense

Range expansion of an exotic Asian snail (Melanoides tuberculata)
into Central Texas rivers, and the parasitological consequences thereof

Name: Stephen Harding

Major Advisor:  David Huffman        

Committee Members:  David Rodriguez and Jake Jackson (BIO-WEST)

Wednesday, 11/02/2016, 11:00 a.m., FAB130

The invasive gastropod Melanoides tuberculata (family: Thiaridae) has been established in Texas since the 1960’s.  After being restricted to thermally stable spring runs for decades, these snails have recently exhibited unprecedented range expansions into the surface-fed Guadalupe and lower San Marcos Rivers in Central Texas.  The mechanisms driving this expansion are not yet understood but parasitic consequences of this phenomenon are such that the invasive Asiatic trematodes Centrocestus formosanus, Haplorchis pumilio, and Philophthalmus gralli are likely to follow their snail hosts into novel habitats from which they were previously excluded.  Morphometric methodologies are utilized to qualitatively and quantitatively partition variation observed within and among Texas snail populations.  Additionally, geometric estimates are used to further partition subtle variation in conch morphology.  Snails exhibiting unique combinations of phenotypic traits were subject to molecular analyses using primers targeting the mitochondrial 16s rRNA gene.  Genetic analyses revealed cryptic variation and diversity within and among Texas snail populations.  Local snail invasions are placed into a global context by establishing phylogenetic relationships with other thiarid snails using 16s rRNA data published in GenBank.  This molecular perspective can now serve as a platform for futures studies investigating habitat & thermal preferenda and further studies of the genetic diversity of local M. tuberculata.

Bio: Stephen Forrest Harding graduated from Texas State University – San Marcos with a BS in Aquatic Biology in 2014.  He entered the MS Aquatic Resources program under the tutelage of Dr. David Huffman in the spring of 2015.  When he is not in the lab he is usually fishing, but can also be found spending time with his fiancée Hope and their two dogs and three kitties.


Thesis Defense

Gender Differences in Student Attitudes Towards Science in Secondary Classrooms with Resident Scientists in Texas

Name: Lisa Maria Hanson

Major Advisor: Dr. Julie F. Westerlund, Ph.D              

Committee Members: Dr. Paula Williamson, Ph.D. and Dr. Hong-Gu Kang, Ph.D

Wednesday, November 2, 2016, 10:30 AM, Norris Conference Room

The purpose of this two-year study was to examine secondary school students’ attitudes about science in four different categories before and after being with PhD graduate students, resident scientists, in their classrooms every week. The study was based upon a National Science Foundation (NSF) program called Project Flowing Waters, a five-year NSF Graduate STEM Fellows in K-12 Education (GK-12) program. The program funded 26 doctoral students, known as NSF GK-12 fellows, who served as bi-weekly resident scientists in science classrooms in local schools.  A newly developed science attitude survey, My Attitude Toward Science Scale (MATS) was used to survey student [n=1111 students] attitudes (Westerlund & Hillman, 2012).  Student attitudes were surveyed in four categories  (a) the subject of science, (b) the desire to become a scientist, (c) the value of science to the society, and (d) the students’ perceptions of scientists.  Matched pre and post student attitude surveys were obtained.  Seventeen resident scientist/teacher partnerships were analyzed, involving 1111 students, in the 2011/12 and 2012/13 school years using a quantitative design.   A control population of students that did not have resident scientists were surveyed in the 2015/16 school.  Both pre and post  surveys were administered at the beginning and again at the end of the school year. Results indicated significant gender differences in attitude changes in some but not all of the four categories.

Bio: Lisa Maria Hanson graduated from Southwestern Adventist University with a BS in Biology and Business and a MS in Science Education from Touro College. She served as an Educational Coordinator in New York City where her passion for STEM education emerged to encourage more women and minorities in STEM careers. Currently, she is an Anatomy and Physiology Instructor at Coastal Bend Community College. Her passion is to establish a STEM summer camp organization in her home country of Jamaica that will encourage young girls to pursue STEM careers.

Thesis Defense


Name: Bianca Alexandra Hernández

Major Advisor: Astrid N. Schwalb, Ph.D              

Committee Members: Dr. Thomas B. Hardy, Clint Robertson, and Dr. David Rodriguez   

Tuesday, November 1, 2016, 9:00 AM, FAB Conference Room 130


Freshwater mussels are one of the most imperiled groups of aquatic organisms. Burrowing and horizontal movement of freshwater mussels are behaviors integral to their ecology, yet mussel behavior is still relatively understudied. Thus, more insight into mussel behavior is needed to establish effective survey protocols and to inform the development of long-term conservation strategies. My objectives were to 1) examine and compare burrowing depth in the field among species and sites in the Guadalupe and San Antonio Rivers; 2) examine the effect of (a) differences in species, (b) decreases in temperature and (c) different substrates on burrowing behavior in experimental studies; and 3) examine the effect of dewatering on movement behavior.

Seasonal differences were found at two sites in the San Marcos and Guadalupe River, with more mussels burrowing deeper in winter. In contrast, this was not observed at a predominately sandy site in the San Antonio River, where mussels were burrowed significantly deeper compared to the other gravel/cobble dominated sites, independent of season. Lab experiments showed that differences in substrate affected burrowing behavior, and mussels responded to temperature changes. Burrowing depth was significantly deeper in sand compared to gravel. Further, when temperature was decreased from above 20°C to 15°C, 9% of the mussels stopped burrowing in sand but 58% stopped in gravel. Significant differences between species were only found in lab experiments with sand, in which Amblema plicata burrowed significantly deeper than Quadrula aurea.

Horizontal movement rates differed significantly when comparing dewatering rates. At the fastest dewatering rate, 100% of the mussels became stranded, whereas 20 to 30% became stranded during slow and moderate dewatering rates. Thus, mussels in Central Texas may not have the ability to respond fast enough when water levels change rapidly, e.g., due to operations of dams. Our results also suggest that surveys may need to follow different guidelines depending on local conditions.

Bio: Bianca Alexandra Hernández graduated from St. Edward’s University with a BA in International Relations in 2008. She interned for Congressman Lloyd Doggett, Austin and taught abroad in Andalucía, Spain before entering the MS Aquatic Resources program (Schwalb Stream Ecology Lab) in the Spring of 2015. She is a proud dog-mother of two: Bruce and Boris. 

Thesis Defense





Name: Cory Scanes

Major Advisor:  Dr. Timothy Bonner            

Committee Members:   Dr. Caitlin Gabor and Dr. Kenneth Ostrand

Friday, November 4, 2016; 10:30 am. FAB 104

 Abstract: Spring complexes within the arid region of the Edwards Plateau are diversity hotspots and evolutionary refugia for numerous aquatic fauna.  Within the last 100 years, anthropogenic modifications and uses of spring complexes are associated with imperilment of aquatic fauna.  Purposes of this study were to quantify current community structure and habitat associations and to assess biotic integrity of the fish community within the Comal springs complex, the greatest discharge spring within the Edwards Plateau region of central Texas and located within the urban landscape.  Fishes and habitats were quantified among wadeable and non-wadeable areas and among six reaches of the Comal springs complex seasonally for one year.  Twenty-five species and 23,318 fishes were observed. Spring-associated fish richness was six, comprising 77% of the total catch per unit area.  Compared to reference conditions and to historical records, species occurrences and relative abundances suggest that the Comal spring complex has high biotic integrity despite extremely low flow conditions and rotenone treatment in the 1950s and habitat modifications (e.g., low head dams, land use conversion, bank stabilization) and high recreation use since the 1950s.  However, the fish community was not homogenous among all reaches.  Within two reaches of high recreational use (i.e., New Channel and Lower River), spring-associated fish richness and relative abundances were lower than other four reaches but still maintained high relative abundances of the federally-listed Fountain Darter.  Fish-habitat associations were similar to reported habitat associations for most fishes.  A notable exception was observed for the Fountain Darter, which had a more ubiquitous distribution and was not strongly associated with vegetation. Into the future, observations quantified in this study can be used as a baseline to monitor and assess threats to the Comal spring complex.

Bio:  Cory Scanes graduated from Texas State University with a BS in Biology in 2014.  He entered the MS Aquatic Resources program in the Fall of 2014 studying community ecology of fishes under Dr. Timothy Bonner.  He is currently a senior research associate at the Environmental Institute of Houston at the University of Houston-Clear Lake.

Thesis Defense

Dispersal of Zebra Mussels, Dreissena polymorpha,

Downstream of an Invaded Reservoir

Name: Jenae Olson

Major Advisor: Dr. Astrid N. Schwalb                  

Committee Members: Dr. Todd Swannack, Dr. Robert McMahon, Dr. Weston H. Nowlin

Friday, November 4, 2016; 9:30 am. FAB Conference Room 130

Abstract: Zebra mussels recently invaded Central Texas and more information is needed to predict their spread in this region and inform management decisions. Therefore, I examined riverine zebra mussel dispersal, settlement, and growth downstream of Lake Belton, TX, invaded by zebra mussels in 2013. Veliger samples and settlement of juveniles on artificial substrate was monitored at a site in the lake and six sites in the Leon and Little Rivers, 0.4 to 54.7 river kilometers (rkm) downstream of the lake outlet. Veliger declined downstream from highest concentrations from sites closest to the lake outlet (0.4 and 2.5 rkm) and were found up to 13 rkm downstream. This decline was represented best with a logarithmic decline in May, Aug, Oct 2015 (R2 = 0.75 to 0.94), and with an inverse power relationship in June and September 2015 (R2 = 0.53 to 0.73). No clear pattern was found in April 2016 (R2=0.32, p = 0.06). In contrast, maximum juvenile settlement (437 ± 75 m-2) occurred 2.5 rkm downstream in August 2016, but not immediately downstream of the lake. Differences in settlement rates between sites could not be explained by differences in physico-chemical parameters such as temperature or turbidity as they did not differ significantly between sites. No mussels were found at 27 and 55 rkm downstream on artificial or natural substrata between May through December of 2015, but juvenile mussels were found there in April 2016. This suggests that zebra mussels were dispersal limited in 2015, and were able to disperse farther in 2016 probably facilitated by high discharge.

Bio:  Jenae Olson graduated from Minnesota State University, Moorhead with a BS in Biology with an Emphasis in Ecology in May, 2014.  She entered the MS Aquatic Resources program in the Spring of 2015 and joined the Schwalb Stream Ecology lab to work on mussel dispersal. Her interest include aquatic ecology/ecosystems and outreach programs.


Thesis Defense


Laura M. Bliss

Major Advisor: Dr. Joseph Veech              

Committee Members:  Dr. Thomas R. Simpson, Dr. Ivan Castro-Arellano

Monday, October 10, 10 AM, Supple 257

As the human population increases worldwide, urbanization, habitat destruction, and habitat modification also increase. Recently the urbanization rate in Central Texas has become one of the highest in the nation. The consequential loss of natural habitat could jeopardize native wildlife species that are already somewhat limited in their distribution. Based on specialized life-history traits that limit large-scale mobility, kangaroo rats (Dipodomys spp.) have been found to be especially sensitive to urbanization-induced habitat modification and fragmentation. Dipodomys compactus is one of five kangaroo rat species found in Texas; this species has narrow, specific habitat requirements. Using a geographic information system (GIS)-based habitat suitability model, I determined that due to isolation among suitable habitat patches, actual D. compactus range in south-central Texas is highly fragmented, and the particular population in south-central Texas may be more isolated than currently thought. The assessment strategy of GIS habitat mapping can be broadly applied to other vulnerable species with similarly narrow habitat parameters to predict current and future management requirements.

 Laura Bliss was born in Houston, Texas and earned an Ecology and Evolutionary Biology B.Sc. and a Chemistry B.A. from the University of California, Santa Cruz in August 2010. Upon graduation, she worked as an ESL teacher in Beijing, China for three years. In the fall of 2013, Laura returned to the United States to complete a seabird research apprenticeship program at Friday Harbor Labs, Washington. Laura entered the Wildlife Ecology M.Sc. program at Texas State University in Fall 2014 and began working with Dr. Joseph Veech. Presently, she works concurrently as a NOAA NWFSC Hammond Research Station Fisheries Biologist and the Outreach Coordinator for a student sustainability organization at the University of Texas at Austin. She and her husband, David Dickey, have a 19-year-old cat of whom they are very proud.

Dissertation Proposal Defense


Plant effects on the dynamics of Frankia populations in soil


Seifeddine Ben Tekaya

Major Advisor: Dittmar Hahn

Committee Members: David Rodriguez, Robert McLean, Jeffrey O. Dawson (UIUC), Mark Paschke (CSU)

Friday, October 7, 2016, 9:00am, Supple 257

Frankiae are slow growing actinobacteria that are able to form root nodules with some woody non-leguminous plants. Studies on the ecology of these bacteria are hampered by difficulties to isolate them into pure cultures which was a prerequisite for quantitative analyses in the past. We have therefore focused on the development of molecular approaches that allow us to retrieve quantitative data from environmental samples unbiased by the limitations of culturability. A first objective of the current study was to develop qPCR based methods to distinguish groups within the genus and quantify their populations in soil. Additional attempts were made to distinguish and quantify typical, nitrogen-fixing frankiae from atypical, generally non-nitrogen fixing frankiae. Both SybrGreen- and Taqman-based qPCR methods were subsequently evaluated for the quantification of these populations in different soils. These methods are then used to study long term effects of agricultural management practices on abundance and diversity of frankiae. Data from these analyses are contrasted with Illumina sequencing data. Both qPCR and Illumina sequencing methods are also applied in analyses of microcosm experiments aiming to investigate the effects of plants species on indigenous and introduced populations of Frankia and relate abundance/diversity to root nodule populations.

Bio: Seif was born in Carthage, Tunisia, in May 13th, 1984. He completed a BS degree in Biological Sciences at the University of Tunis el Manar in 2007, and earned an MS degree in microbiology from the same university with a research thesis that focused on the diversity of ascomycetes in high saline lakes in 2009. In 2014, he joined the PhD program in Aquatic Resources at Texas State University.

Thesis Defense


Name: Ovie Agare

Major Advisor:  Dr. Thom Hardy                 

Committee Members:   Dr. Weston Nowlin and Dr. Benjamin Schwartz

Thursday, October 13, 2016; 8:00 am. FAB Conference Room 130

 Abstract: In the San Marcos River, recreational activities are most pronounced between April and October. Given the continued urbanization and increasing population in San Marcos there is need for a quantitative study on the possible effect of elevated recreational activities on the aquatic macroinvertebrates within the river. Currently, no study has quantified both patterns in macroinvertebrate drift and benthic community structure simultaneously in the San Marcos River.  Information on drift patterns and benthic macroinvertebrate habitat relationships is necessary to understand mechanisms for species persistence within the San Marcos River.  In this study, I examined the seasonal and longitudinal patterns of benthic macroinvertebrate community composition at three different sites within the San Marcos River. I also examined the seasonal and longitudinal response of the drifting aquatic macroinvertebrates to changes in their habitat as a result of high recreational activities in the San Marcos River. Tubing and swimming accounted for most of the recreation activity (>90%).  Across all seasons, Site 1 had the highest drift densities compared to Site 2 and Site 3. CCA result explained 15.3% of the variability in the San Marcos River benthic macroinvertebrate community among vegetation habitats and 23.9% among open substrate habitats. Study results indicated that drift may be dependent on the benthic abundance. Macroinvertebrate drift densities followed the typical circadian pattern observed in other river systems and result indicated no increase in macroinvertebrate drift density during the day when recreation is occurring. Conclusively, Study results indicated that macroinvertebrates at Site 1 and 2 were not impacted by recreation and turbidity. However, Site 3, based on the CCA results indicate that substrate and turbidity are factors influencing the macroinvertebrate community.

Bio: Ovie Agare graduated from the University of Lagos with a BS in Surveying and Geoinformatics in 2008. His interest for life within rivers in his homeland and a quest to find ways to improve the quality of water at home made him pursue a MS in Aquatic Resources. He joined the MS Aquatic Biology program at Texas State University in the Fall of 2013 and has since worked with Dr. Thom Hardy at the Meadows Center for Water and the Environment.

Summer 2016

Thesis Defense

Soil and vegetative associations of heteromyid rodents in central and South Texas with comments on trapping techniques

Michelle E. Adcock

Major Advisor:  Dr. Thomas R. Simpson

Committee Members:  Dr. M. Clay Green, Dr. Richard W. Manning, and Dr. Joseph A. Veech                               

Tuesday, July 12, 2016; 1:00 PM; Norris Room; Jerome and Catherine Supple Science

Heteromyid rodents occur in arid and semiarid lands in western North America. Members of this family often form assemblages that are found in habitats with sandy soils and vegetation that offers both open areas and dense shrub cover.  In this study I investigated the soil and vegetative associations for heteromyid communities at the landscape and microhabitat scales in Central and South Texas.  I utilized capture success as a proxy for abundance.  As a minor objective, I investigated the capture success of Dipodomys compactus/ordii, the most trap-shy heteromyid species included in this study.  I trapped for heteromyids for three seasons on two study sites (Guadalupe County and Jim Hogg County) and assessed microhabitat parameters, including herbaceous cover of grasses and forbs, bare ground, leaf litter, and densiometer readings within each treatment.  Treatments were defined as a combination of both land cover and soil type.  For the landscape level analyses, capture success was significantly different per treatment for each species on both study sites.  Heteromyid species either: 1) selected for a treatment, 2) avoided a treatment, or 3) occurred as expected within a treatment based upon the overall availability of the particular land cover category and soil type.  Selection for or avoidance of certain land cover and soil types on the landscape scale could suggest habitat partitioning by heteromyid species.  For the microhabitat analyses, herbaceous cover and bare ground were significant for the capture success of C. hispidus on the Jim Hogg County study site, with a positive trend observed for herbaceous cover (β = 0.1259, R2 = 0.1516, P = 0.0276), and a negative trend observed for bare ground (β = -0.2156, R2 = 0.2477, P = 0.0038).  Microhabitat parameters were not important predictors of capture success on the Guadalupe County study site, perhaps because of a homogeneous landscape, when compared with the Jim Hogg County study site, which offers more heterogeneity for heteromyid species.  For the paired trap study, extra-large folding H.B. Sherman traps had the highest probability of capture success for D. compactus/ordii.

Michelle Adcock was born in Staunton, VA and earned her B.S. from the University of Tennessee-Chattanooga in 2005 with a major in environmental science and a concentration in biology. Upon graduation, she worked as an educational outreach coordinator at a rescue, rehabilitation, and release marine aquarium for two years. Concurrent with and after this position, she worked as a wildlife and wetland consultant in Florida for seven years. She entered the M.S. program in Wildlife Ecology at Texas State University in fall 2012 working with Dr. Thomas R. Simpson. She and her husband, Zach Adcock, are proud parents to their son, Davis.

Thesis Defense

Distribution of phosphorous, forms of phosphorous and physical composition of sediments in four central Texas reservoirs.

Wayne Waring

Major Advisor: Dr. Alan Groeger              

Committee Members: Dr. Alan Groeger, Dr. Vicente Lopes, Dr. Julie Westerlund   

Thursday, July 7, 3:00 PM, FAB 130

Phosphorous (P) is a limiting nutrient in many aquatic ecosystems. Generally, most of the P in a reservoir is delivered in the inflowing river(s) as suspended particulates, and eventually settles to the bottom sediments. The P is then alternately sequestered and released through nutrient cycling processes. The purpose of the present study is to evaluate the P content and gross physical composition of sediments in four Texas reservoirs; including one small run-of-the river reservoir (L. Dunlap), and three, large deep-storage reservoirs (L. Amistad, L. Buchanan, and Canyon L.). Surface sediment samples were collected from 31 sites in the four reservoirs and analyzed for total phosphorous (TP), P fractionation and sediment composition including organic matter, calcium carbonate and non-carbonate clastics. Overall, the HCl-P fraction, which is mostly Ca-bound P, was the best predictor of TP among the P fractions. In L. Amistad, clastics content was the physical parameter with the greatest positive relationship to TP. The reservoir also showed distinct differences in the two contributing arms. P was higher in the Rio Grande arm compared to the Devils River arm, as was the clastics content of the sediments. TP in L. Buchanan showed a clear longitudinal increase between the headwaters and the dam. Ca-bound P was the greatest P fraction in all reservoirs except for L. Dunlap, which had a larger proportion of NaOH-P (iron-bound, redox sensitive P). In both Canyon L. and L. Dunlap, OM was the physical fraction with the strongest relationship to TP. L. Dunlap appears to be functioning differently from the other reservoirs regarding phosphorous dynamics. One speculative possibility is that shorter WRT and fewer periods of strong stratification result in limited release of iron-bound phosphorous under anoxic conditions, thereby providing greater retention of iron-bound phosphorous. Information from this study may prove useful in understanding these differences.

 Bio: Wayne Waring is originally from Austin, Texas and a resident of San Marcos, TX for the past 12 years. He attended Texas State University in San Marcos, TX for his B.S in Aquatic Biology. Wayne began the Masters of Science in Aquatic Biology in the Aquatic Resources program at Texas State University in the Fall semester, 2010. While at Texas State, he received the Outstanding Academic Achievement Award in 2013, 2014 and 2015; and the Outstanding Science Education Award in 2015.

 Thesis Defense


Name: Kendall Jacquelle AuBuchon

Major Advisor: Dr. Thomas (Randy) Simpson                            

Committee Members: Dr. Mark Elbroch and Dr. Butch Weckerly       

July 1, 2016; 2:00 PM; Norris Room; Jerome and Catherine Supple Science

The understanding of activity patterns and hunting behaviors can provide insight into life history and predator-prey dynamics. The mountain lion, Puma concolor, occupies the largest geographical range of any terrestrial mammal in the western hemisphere. Mountain lions live in a variety of habitats including mixed forests, high elevation plateaus, shrub communities, open steppe, valley bottoms with steep slopes, and riparian habitats. Previous research has shown their activity patterns occur primarily during the nocturnal and crepuscular periods. The primary prey of mountain lions are mule deer and elk, but they also rely on smaller prey such as American beaver and North American porcupine among others. I investigated characteristics of mountain lion kills in response to diel cycle and lunar illumination. Data were collected between March 4, 2011 to April 27, 2015 on a total of 1,234 predation events from 25 different mountain lions fitted with Global Positioning System (GPS) collars in Colorado and Wyoming. My three objectives were: to provide descriptive characteristics on mountain lion kill sites, evaluate selectivity of kills made across the diel cycle and over varying degrees of lunar illumination, and to assess whether there are seasonal differences in the proportion of kills made across the diel cycle, and across the lunar illumination categories. I constructed 95% Bonferroni adjusted confidence intervals and Manly’s alpha selectivity index scores to assess selectivity or avoidance of specific categories. I used R to run chi-square tests and found that there was a significant difference between lunar illumination categories and during the summer season. The greatest proportion of kills occurred during periods with greatest lunar illumination (>90 %). There was a significant difference in prey selection at the lowest level (<10%) of lunar illumination. Diel cycle also had significant effects on mountain lion kills. Understanding mountain lion hunting behaviors will aid in management of this predator as well as management of its prey populations. In an era of technological advances and urban growth and development, these management practices will allow us the knowledge and tools to successfully cohabitate with this iconic species.

 Kendall AuBuchon grew up in Austin, TX and attended high school at McCallum Fine Arts Academy. In spring 2013 she graduated from Texas State University where she received a BS in Wildlife Biology. She worked with Dr. Noland Martin for undergraduate research investigating mechanisms of hybridization in Iris nelsonii. During her undergraduate degree she accepted an internship position working as a field technician in Colorado where she met Dr. Mark Elbroch, who was conducting his own research at the time. She began her MS in Wildlife Ecology at Texas State University in fall 2013 working with Dr. Randy Simpson. She and Dr. Mark Elbroch began collaborating for her MS where she worked on a large dataset investigating different parameters of kill site data from Mountain lions in Colorado and Wyoming.     

Thesis Defense

Characterization of IBR5-ROP GTPase (ROP2/ROP6) Interaction in Plant Auxin Response

Elia Lopez

Major Advisor: Dr. Nihal Dharmasiri

Committee Members: Dr. Rachell Booth, Dr. Dana Garcia and Dr. Hong-Gu Kang

Friday, July 1, 2016; 10:00 AM; Norris Room, Supple Science Building

The quintessential phytohormone auxin regulates many aspects of growth and development throughout the plant life cycle. Diverse auxin responses occur via multiple distinct and overlapping signaling pathways. It is well documented that auxin exerts control over gene expression by binding its nuclear co-receptors TIR1/AFB family F-box proteins and AUX/IAA transcriptional repressor proteins, thereby promoting polyubiquitination and subsequent degradation of AUX/IAAs and relieving transcriptional repression of auxin-responsive genes. More recently, auxin has also been shown to rapidly activate Rho of plant (ROP) GTPases at the plasma membrane, leading to a variety of cellular responses. The auxin signaling mutant ibr5-1 exhibits reduced auxin-responsive gene expression without accumulation of AUX/IAA repressor proteins, suggesting the dual-specificity protein phosphatase encoded by the gene IBR5 independently regulates the processes of AUX/IAA degradation and auxin-induced gene expression. In a previous screen for IBR5 interactors, a small GTPase was identified, prompting the question of whether IBR5 interacts with the ROP GTPases ROP2 and ROP6, which have been shown to be involved in auxin signaling pathways in the cytoplasm. In vitro interaction assays indicated IBR5 interacts with ROP2 and ROP6, and these interactions were confirmed by co-immunoprecipitation in Arabidopsis thaliana. To assess genetic interaction, ibr5-1 rop6-2 double null mutant was generated. In root growth assays for auxin inhibition of primary root elongation or induction of lateral root formation, the double mutant exhibited auxin resistance similar to the ibr5-1 parent line. Taken together, the results suggest the dual-specificity phosphatase IBR5 physically interacts with the Rho-like GTPases ROP2 and ROP6, and these proteins may function in a common auxin signaling pathway.

Bio: Elia Lopez graduated from Texas State University in 2013, earning a B.S. in Biology with a minor in Geography. In 2014, she joined the M.S. program in Biology at Texas State University where she is studying plant hormone signaling pathways. During her time in the graduate program, she became a South Texas Doctoral Bridge Program Scholar and received an award for Best Poster at the 20th Annual Department of Biology Colloquium. In the Fall, she will begin pursuing a PhD at the University of Texas Graduate School of Biomedical Sciences (MD Anderson Cancer Center/UT Health Science Center at Houston).

Thesis Defense


Name: Kathryn Michelle Benavidez
Major Advisor: Dr. Iván Castro-Arellano                           

Committee Members: Dr. Dittmar Hahn, Dr. David Rodriguez, and Dr. Joseph Veech      

July 1, 2016; 9:00 AM; Room 153; Jerome and Catherine Supple Science

Leptospirosis is thought to be the most widespread zoonotic disease in the world.  For this study 124 mice (Mus musculus), 99 rats (Rattus rattus and R. norvegicus), and 89 small Asian mongooses (Herpestes auropunctatus) from five farms in Puerto Rico were tested for renal carriage of Leptospira and approximately 38% of the sampled individuals were positive I evinced a heterogeneous distribution of Leptospira prevalence among the sites with a farm in Lajas having the highest prevalence at 52%.  Among tested species, mice had the highest prevalence of Leptospira at 59% and mongooses had the lowest at 13%.  Comparative sequence analysis of the LipL32 gene revealed the presence of two species of Leptospira: Leptospira borgpetersenii and Leptospira interrogans.  These two Leptospira species were equally distributed at all farms except for a farm at San Sebastián where 100% of the samples sequenced were of the species L. borgpetersenii.  Significant associations of Leptospira prevalence with landscape features were observed at a farm in Naguabo, where more positive samples were located near all the tested landscape features and at a farm in Sabana Grande where more positive samples were found near a human dwelling. These results show that rural areas of Puerto Rico are in need of management and longitudinal surveillance of Leptospira in order to prevent continued infection of Leptospirosis by focal susceptible species (i.e. humans and cattle).

Michelle Benavidez was raised in South Texas and attended high school at Skidmore-Tynan ISD.  In Spring 2014 she graduated as a McNair Scholar from St. Edward’s University in Austin, TX where she received a BS in Environmental Science and Policy with a concentration in Biology and a minor in Sociology.  For her undergraduate research she worked with Dr. Peter Beck to investigate the effects of border fence construction on ocelot conservation efforts in Texas.  She began her MS in Wildlife Ecology at Texas State University in Fall 2014 working with Dr. Iván Castro-Arellano to investigate the role of the small mammals in disease transmission on the island of Puerto Rico.  Fall 2016, she will begin a PhD program at Indiana University in Bloomington where she will join Dr. Michael Wasserman’s Primate Environmental Endocrinology Lab in the Anthropology Department.

Thesis Defense

Fitness of Escherichia coli when in Mixed Culture with Enterococcus faecalis

Avry Stolzman

Major Advisor: Dr. Robert JC McLean  

Committee Members: Dr. Kavita Kakirde and Dr. Kelli Palmer (UT Dallas)

Thursday, June 30, 2016; 1:00 PM; Norris Room, Supple Building

   Escherichia coli (E. coli) coexists with many different species, such as Enterococcus faecalis (E. faecalis), in the gastrointestinal tract of many animals Under normal circumstances, the two bacteria live alongside each other and a multitude of other microorganisms without causing infection. However, there are occasional instances when an imbalance occurs and certain flora are able to outcompete the rest. These superior bacteria express specific traits that allow them to increase colonization and infect the host organism. There is currently little known about the mechanism of how E. coli is able coexist. Using the Keio collection of E. coli, we identified that the gene yliK in E. coli, commonly known as methylmalonoyl CoA mutase, that is essential for its growth when in mixed culture with E. faecalis. Methylmalonoyl CoA mutase is part of a four gene operon encoding for enzymes that convert succinate into propionate. The E. coli mutant pure culture exhibited increased fitness with the addition of propionate. The E. faecalis, although at a much lower cell density, also exhibited increased fitness with the addition of propionate. The E. coli mutant/E. faecalis mixed culture showed to have increased fitness when grown together as when compared to the fitness of the two bacteria in pure culture. The E. coli mutant/E. faecalis mixed culture also showed an increase in fitness with the addition of propionate. These results suggest that E. coli and E. faecalis increase the other’s fitness, and that this elevated fitness is enhanced when propionate is added to the environment.

Bio: Avry Stolzman is a hill country native, growing up in Johnson City, Texas. She graduated from Tarleton State University in 2013 with a B.S. in Biology. She began her M.S. in 2014 studying the relationship between Escherichia coli and Enterococcus faecalis in mixed culture. She will be attending Ross University School of Veterinary Medicine in September of 2016.

Thesis Defense

Salmonellae in the intestine of H. plecostomus in the San Marcos River

Name: Anna Y. Gates
Major Advisor: Dr. Dittmar Hahn

Committee Members:   Dr. Robert McLean and Dr. Thom Hardy

Thursday, June 30, 2016, 9:00 am, Supple 153

Heavy rainfall events have been associated with outbreaks of many waterborne diseases including salmonellosis. Salmonellosis is caused by members of the genus Salmonella that can enter water systems through sewage contamination, runoff after heavy rainfalls, or flow-through channels through manure fields after heavy rains or flooding.  Currently, salmonellae are not closely monitored in regards to water quality.  In this study, Hypostomus plecostomus, an invasive, algae consuming fish, was sampled from the San Marcos River (San Marcos, TX), the intestines analyzed for the presence of salmonellae by quantitative real-time polymerase chain reaction (qPCR) after semi-selective enrichment, and results related to precipitation and other ecological factors affecting the river area.  Salmonellae were detected in the intestines of H. plecostomus in 40-100% of the fish following most precipitation events, but were not consistently detected in environmental samples (i.e. water and sediments).  Other ecological factors affecting the river do not appear to play a significant role in the prevalence of salmonellae in the intestines of H. plecostomus.  This leads us to believe that H. plecostomus is ingesting salmonellae through their food sources and that the amount of salmonellae present in those food sources may be increasing after large rainfall events, but may not be dependent on these events. 

Further studies included characterization of Salmonella isolates from positive samples by repetitive polymerase chain reaction (rep-PCR).  Unique isolates were then serotyped using Multilocus Sequence Typing (MLST).  Several sampled H. plecostomus were observed to be infected by multiple serotypes of Salmonella, whereas other positive fish were observed to be infected by one serotype only.  Some serotypes were observed to be common across multiple sampling dates, which leads us to believe that there may be a common environmental serotype residing in the intestines of infected H. plecostomus.  Furthermore, detection of multiple serotypes in the intestines of H. plecostomus was an unexpected observation.          

Anna Gates received her Bachelor’s degree from the University of Houston – Downtown in microbiology in 2012, where she participated in undergraduate research studying dental biofilms and stress on B cell lymphocytes.  She started the Master’s degree program and joined Dr. Hahn’s lab in 2014, studying microbial ecology and the prevalence of salmonellae.  She will be joining Michigan State University to pursue a Doctor of Veterinary Medicine degree in August 2016.  

Thesis Defense

Histone variant H2A.Z substitution mediated by the SWR1-like complex is a novel transcriptional regulatory mechanism controlling defense genes and immunity in plants

April Bonnard

Major Advisor: Dr. Hong-Gu Kang            

Committee Members: Dr. Nihal Dharmasiri and Dr. Sunethra Dharmasiri          

Friday, June 24, 2016; 2:00 PM; Norris Room, Supple Building

 Plants have evolved a complex immune system against various pathogens, part of which involves the function of resistance (R) proteins in detecting the presence of secreted effector molecules from pathogens. This detection leads to a robust immune response by implementing large-scale modifications in chromatin accessibility, thus leading to transcriptional reprogramming. MORC1 is a protein that interacts with several of these R proteins and is required to maintain optimum levels of immunity in Arabidopsis. MORC1 is also a putative chromatin-remodeling factor as it has been shown to exhibit ATPase and endonuclease activity and that its subpopulation localizes to the nucleus after pathogen infection. In this research, I aim to characterize the interaction of MORC1 with the components of the SWR1-like complex, including ACT1, ARP4, SWC2, SWC5, SWC6, SUF3, PIE1, RVB1, and YAF9 in Arabidopsis. The SWR1-like complex replaces histone H2A with its variant H2A.Z. This replacement has been speculated to be involved in transcription regulation as it occurs in the promoter and/or genic region of actively transcribed genes. Interestingly, a wide range of mutations in these SWR1-like components led to altered resistance to the bacterial pathogen Pseudomonas syringae, suggesting that the SWR1-like complex functions in plant immunity. To further gain insight into the molecular mechanism of this H2A.Z replacement in defense signaling, I performed chromatin immunoprecipitation with H2A.Z and found that pathogen infection leads to the association of H2A.Z with defense genes including PR-5. Furthermore, an Arabidopsis mutant line lacking three genes encoding H2A.Z showed compromised transcriptional induction of defense genes in response to pathogen infection. Together, my results establish that the histone replacement with H2A.Z by the SWR1-like complex modulates the transcription of defense genes and thereby affects immunity in plants. A potential model how this histone replacement can be implicated in transcriptional memories in which a prior stress exposure often leads to more prompt transcriptional induction to similar stress will be discussed.

Bio: April Bonnard graduated from Texas State University in 2014 earning a B.S. in Biology with a minor in Biochemistry. She is now pursuing her M.S. in Biology at Texas State University where she is studying the relationship between chromatin-remodeling and plant immunity. During her time in the M.S. program, she became a member of the Alpha Chi National College Honor Society and participated in the 20th Annual Department of Biology Colloquium, where she received an award for the best talk at the M.S. level.

Thesis Defense

Effects of red imported fire ants (Solenopsis invicta) on juvenile Houston toads (Bufo houstonensis) in coastal prairie grassland


Name: Madeleine Marsh

Major Advisor: Dr. Michael Forstner

Committee Members: Dr. Thomas Simpson and Dr. Clay Green

Wednesday, June 22, 2016, 10:00 am, Supple Norris Room

The Houston toad (Bufo houstonensis) was first described in 1953 in Houston, Texas, but has since been extirpated from the area. Houston toad populations have been in a nearly continuous decline across their known distribution since discovery, primarily due to multiple stressors, including red imported fire ants (Solenopsis invicta; hereafter referred to as RIFA).  In spite of the uncertainty of historical presence, the 1984 Recovery Plan attempted to reintroduce the Houston Toad into coastal prairie habitats.  Although originally thought unsuccessful, the Recovery Plan site proved to be suitable habitat, even if only as dispersal habitat. In 2015, on Attwater Prairie Chicken National Wildlife Refuge (APCNWR), a total of forty-eight exclosures were placed in four prairie locations (12 exclosures per site) two of which were treated for RIFA and two prairie locations were used as untreated controls. Morphometric data (snout-urostyle length, head-width, and weight) were collected for all toadlets were detected on a weekly basis, slowing to bi-weekly after six weeks.  A mixed-effects for repeated measures model was used in R to evaluate growth rates between treatment and control areas, which showed no difference in growth between treatments (f = 1.747, df = 42.7, 45, p = 0.09) or density (t = -1.095, df = 140.61, p > 0.1). Program MARK was used to estimate survivorship and detection between treatments using a Cormack-Jolly Seiber (CJS) model.  The model chosen, using ΔAICc, assumed that detection and survivorship changed through time but not between treatments.  Because there was no difference in growth or survivorship, we fail to reject our null hypothesis that RIFA has a negative impact on the survival and growth of juvenile Houston Toads. A trend seen in the data comparing the exclosures in the open prairie to those within the drip line showed higher survival within the drip line, but much faster growth in the open prairie.  This supports that connectivity of habitats is vital for the survival of juvenile Houston toads.  However, because it has been shown that Houston toads are able to persist on the RIFA controlled prairies of APCNWR, the area of suitable Houston toad habitat can now be more explicitly delineated to include native grasslands, particularly for dispersal habitat.  These landscape-connecting habitats are one of the most critical and least understood ecological aspects for Houston toad management. The results from this study also clearly assist with assessing new sites for reintroduction through propagation and population restoration efforts.

Thesis Defense

Site factors influencing drought-related tree mortality in Central Texas

Name: Beth Crouchet

Major Advisor: Dr. Susan Schwinning              

Committee Members: Dr. Benjamin Schwartz and Dr. Jennifer Jensen

Wednesday, June 15, 2016, 1:00 pm, Supple 153

Climate models predict an increase in the frequency of severe weather events, including prolonged drought conditions coupled with exceptionally high temperatures. These so called “global-change-type” drought events have been linked to numerous forest dieback events worldwide. Texas experienced such an event in 2011, which reportedly killed 6% of all trees in the state. The purpose of my research was to identify site factors that modified local rates of tree mortality. In 2014, I censused 64 plots across the state, of which 40 were included in the final analysis focusing on Central Texas. Over 6000 trees were included, mostly in the genera Juniperus (n=3487), Quercus (n=1054), Ilex (n=745), Ulmus (n=347) and Diospyros (n=308). Each tree above 10 cm circumference was identified to the species level, its basal circumference was measured and its health status recorded in seven categories between dead with no sign of re-sprouting to < 25% crown die-back. For each plot I also collected site variables describing community composition, elevation, slope, aspect, solar insolation, water storage capacity, soil texture and depth, as well as climate factors, including annual precipitation from 2008 to 2011 and daily temperatures in 2011. I used binary logistic regression in a multivariate model selection analysis to determine which factors were significantly correlated with crown dieback and tree mortality.

The number of days in which trees were exposed to temperatures over 35 or 38°C in 2011 had a significantly positive effect on mortality in three out of nine tree species. Heat exposure had independent effects on crown dieback and on the odds of resprouting. Precipitation in 2011 had significant effects in eight out of nine species, but they were positive for some species and negative for others. Topographic effects (e.g., slope and aspect) were significant for four out of nine species. Collective stand density was not as good a predictor of mortality than species-specific densities. For example, the mortality odds of Juniperus ashei on the Edwards Plateau was more closely related to intraspecific density. Although J. ashei was by far the most common species, Quercus fusiformis was not negatively affected by J. ashei density, but instead by its own intraspecific density and the density of Diospyros texana. Modeling approaches that focus on purely abiotic factors such as climate, topography and soil are incomplete, because they omit the influence of species interactions in diverse communities. My study exposed some of the complexities associated with linking climate events to vegetation changes, in particular, the effects of landscape variation and vegetation composition on tree mortality.


Bio: Beth Crouchet was born in Austin, Texas and earned a B.S. degree in Environmental Science from Concordia University in 2010. She has recently completed the Capital Area Master Naturalist Program where she volunteers as an environmental educator around the Austin area. She is the mother of two boys, ages 11 and 14.

Spring 2016

Thesis Defense

The Genomic Architecture of Reproductive Isolation in a Louisiana Iris Hybrid Zone

Cheng-Jung (Joy) Sung

Major Advisor: Dr. Noland Martin

Committee Members: Dr. Chris Nice and Dr. James Ott

Tuesday, May 31,2016, 10:00am, Supple Science Building, Room 153

Speciation is a consequence of multiple sequentially-acting pre-zygotic and post-zygotic reproductive isolating barriers that evolve over time. To examine the genomic architecture of reproductive isolation and adaptive introgression, hybrid zones can be used to identify genomic regions that are resistant - or more susceptible - to gene flow in nature as well as to identify the genomic architecture of known reproductive isolating barriers. In the current study, a large Louisiana Iris hybrid zone between Iris fulva and Iris hexagona habitats was identified in Southern Louisiana. This hybrid zone is comprised of individuals with a wide variety of genetically diverse late-generation hybrids that exhibit an array of flower-color and plant-growth morphologies. The two Iris species are differentiated with respect to floral traits morphologically, which results in the attraction of different pollinators, and ecologically, which results in habitat isolation. Ecological isolation is therefore one of the most important barriers preventing gene exchange between these Iris species.

In this defense, I will describe how Bayesian Genomic Cline analyses can be used to identify loci responsible for reproductive isolation and adaptive introgression in Louisiana Iris. I also will show how Genome Wide Association Mapping can identify the genomic architecture of floral and ecological traits that differ between I. fulva and I. hexagona. I will then combine these two analytical approaches to ask the following question: “Do the genomic architectures of phenotypic traits predict patterns of gene flow in hybrid zones?” In short, the answer is “yes”. The genomic architectures of 14 traits that were examined were complex, with many loci of small effect explaining phenotypic differences observed between species. Further, these loci were significantly associated with reproductive isolation between, and adaptive introgression across species boundaries.

Bio: Cheng-Jung Sung was born and raised in Taipei, Taiwan and received her Bachelor’s degree of Science at National Taiwan University in Crop Breeding of the Department of Agronomy in Taiwan in 2011. She attended Texas State University and started her Master’s study in the Population and Conservation Biology program of the Department of Biology in 2012 and has been working with Dr. Noland Martin since then. She plans on integrating her two fields of study to pursue her PhD degree.

Dissertation Defense


Personality and predation in a changing environment

Name Chelsea Blake

Major Advisor: Dr. Caitlin Gabor           

Committee Members: Dr. Chris Nice, Dr. Andrea Aspbury, Dr. Alison Bell, Dr. Brian Langerhans


Friday, 15 April 2015, 2:00pm Supple Science Building 116

The interaction between predators and prey is one of the driving forces that shape not only animal behavior, but also the evolution and ecology of organisms. However, predator-prey interactions are now taking place in an unprecedented and rapidly changing world, as humans introduce new species and alter habitat conditions. Thus examining the anthropogenic introduction of novel predators is key to the contemporary study of behavioral ecology. Further, not all individual animals behave the same way within the same species or population, thus it is important to also assess behavior at the level of the individual. Individual behavioral types, or "personalities" of animals can have far-reaching implications for their ecology. Here I have explored predator-prey interactions in the context of changing environments from the perspective of individual-level variation to provide novel insights into species interactions. I have found that the personality of prey can affect how they fare with predators, but that the effect depends on which predator species they face. Additionally, I have shown that although behavioral type is important in predator interactions, it does not affect whether prey are able to recognize a novel predator. I have also explored how physical antipredator characteristics of individuals might relate to their behavioral type. I have found that although physical traits are not necessarily inherently correlated with behavioral traits, altering the physical condition of an individual can affect their behavioral traits. Ultimately, my work contributes to the understanding of how prey personality could interact with introduced predators to either aid or hinder the survival of native species.

Bio:  Chelsea was born in Evanston, IL and grew up in Indianapolis, IN. At Earlham College, a Quaker liberal arts school, Chelsea studied metal working and biology. After graduating in 2008, Chelsea spent several years working in environmental education and ecology around the nation before starting a PhD program at Texas State in 2011. In 2013, Chelsea won a National Science Foundation fellowship, which facilitated the creation of the Project SPRING science outreach program at Texas State. Chelsea’s parents, sister, spouse, Augustyn Blake, and choir friends at Crystal Queer Revelation have been very supportive throughout these years.

Thesis Defense

Title: Effects of Abiotic Factors on Body Size Class Variation of Lepidoptera in Two Contrasting Ecosystems: the Chihuahuan Desert and Edwards Plateau 

Name: Virginia Brown

Major Advisor:  Dr. Michael Huston  

Committee Members:   Dr. David Huffman and Dr. Chris Nice


Wednesday, April 6, 2016, 2pm, Supple 257

The abundance and body sizes of organisms are expected to respond to environmental conditions such as temperature, precipitation, and food availability.   I quantified the abundance and total mass of nocturnal lepidoptera across multiple size classes to determine whether lepidoptera of different sizes responded differently to environmental conditions. Standardized samples were collected from two contrasting ecosystems – the Chihuahuan Desert in the Big Bend region and the Edwards Plateau near San Marcos. During 2013 the Chihuahuan Desert was sampled at two sites, a mountain hillside and a mesquite flat, near Terlingua Ranch headquarters at the base of the Christmas Mountains. Synchronously two sites, an open grassland and an oak-juniper thicket, were sampled at Freeman Ranch near San Marcos, Texas. Samples were sorted to morphospecies, counted, dried and weighed. Body size classes were evaluated in terms of total number of individuals, total weight and morphospecies. Available abiotic factors were not strong predictors of body size patterns. Total abundance and weight followed seasonal precipitation patterns at both locales.   Body-size classes were more strongly correlated to each other in the Chihuahuan Desert than in the Edwards Plateau, probably as a result of the contrasting seasonal precipitation patterns. Our research establishes a baseline of comparison for the Chihuahuan Desert; while demonstrating that there are complex interactions between the lepidoptera community and abiotic factors that warrant further investigation. 

I evaluated how the body size distribution of lepidoptera were affected by abiotic factors; average and accumulative monthly temperature, growing degree days, precipitation, and temperature at time of sampling. To determine if the response was due to phylogeny of the order, rather than environmental factors.


Virginia Brown became interested in studying insects while traveling through the outback of Australia. She joined the Huston Terrestrial Ecology lab as a junior, and helped establish entomological research at the Christmas Mountains. Enjoying her undergraduate research in the Chihuahuan desert she decided to remain at Texas State University for her Masters in Biology with a focus on lepidoptera ecology.

Thesis Defense

Potential role of stygobitic species in nutrient dynamic of the Edwards Aquifer, central Texas

Lauren A. Loney

Major Advisor: Dr. Weston Nowlin  

Committee Members:  Dr. Floyd Weckerly, Dr. Benjamin Schwartz


Wednesday, April 6, 1:00PM, Freeman Aquatic Building 130

In aquatic ecosystems, animals can have direct and indirect impacts on the cycling of nutrients. In subterranean aquatic ecosystems with little to no direct connection to the surface, the recycling of organic matter and inorganic nutrients is likely to be particularly important in maintaining below ground communities.  Although numerous studies have examined the role of consumer-driven nutrient cycling in surface aquatic ecosystems, relatively little is known about the ecology and nutrient cycling dynamics of subterranean ecosystems.  In this study, I examined the nutrient recycling and body stoichiometry of the stygobiont (obligate subterranean aquatic organisms) community located at a site within the Edwards Aquifer, one of the world’s most diverse aquifers.  The first goal of my study was to examine the diversity and composition of stygobionts at my study sight and to gain information on which stygobiont species were numerically- and biomass-dominant in this portion of the Edwards Aquifer.  The second portion of my study examined nutrient recycling (via excretion) and elemental composition of several common invertebrate stygobiont species in my study portion of the aquifer.  I also compared stygobiont nutrient recycling and stoichiometry to related epigean taxa collected from the San Marcos River. Overall, I found that the stygobiont community at my study site was relatively species rich, but it numerically dominated by few taxa.  I also found that stygobiont excretion varied significantly with body size and species identity, but that species origin (epigean vs stygobiont) did not have a substantial role in predicting nutrient recycling and elemental composition.

Bio: Lauren Loney is from San Marcos, Texas. She graduated from the University of Missouri in 2011 with a B.S. in Fisheries and Wildlife. Lauren began her Master’s of Science in Aquatic Resources at Texas State University in the fall semester of 2012 and is currently pursuing a Juris Doctor from the University of Texas with an emphasis in water law. 

Thesis Defense

Urbanization and Stress Response of Texas Eurycea Salamanders

Name: Megan J. Mondelli

Major Advisor: Caitlin R. Gabor, Department of Biology, Texas State University 

Committee Members: Chris Nice, Department of Biology, Texas State University

Andrew Gluesenkamp, Texas Parks & Wildlife and Nathan Bendik, Watershed Department, City of Austin


Wednesday, April 6, 2016, 9AM, Supple 153


Amphibians worldwide are rapidly declining. Successful conservation strategies should consider the physiological response of an organism to its environment using stress hormones. Glucocorticoid (CG) hormones are a particularly useful class of biomarkers that effectively measure stress. The primary GC stress hormone in amphibians is corticosterone (CORT). Short-term increases in CORT (i.e., acute stress) are adaptive during stressful events because CORT mediate metabolic and immune function. However, chronic stress can be harmful to the overall health of an organism and can lead to dysregulation of the hypothalamic-pituitary-interrenal (HPI, for amphibians) axis leaving the organism susceptible to metabolic and immune problems. Chronic stress is also associated with suppressed reproductive hormones such as testosterone and estradiol. Anthropogenic and environmental factors such as seasonal changes, urbanization (modification, pollution) and storms have been shown to affect stress and reproductive hormones. Here, I studied how these factors affect the stress of two federally threatened species of Texas Eurycea salamanders that are fully aquatic. I conducted two projects, the first of which measured stress levels of E. tonkawae, Jollyville Plateau salamander, in urban and rural streams across seasons. I also examined the correlation between stress, sex steroids and activity levels of salamanders in urban and rural streams. My second project investigated the effects of storm water runoff on stress of E. nana, San Marcos salamander. I found that CORT in E. tonkawae is highest in summer but did not vary based on stream type. Activity in E. tonkawae varied by population; one urban stream showed a positive correlation between activity and CORT while but this was not the case in the other populations. However, urbanization did not affect activity level. Additionally, my research shows a significant effect of storm runoff water on testosterone, but not CORT in E. nana. In conclusion, my research shows that CORT changes with season and should be considered when testing other questions stress response. Additionally, it is possible that storm water does not affect the stress of salamanders, but some other factor associated with storm events might be stressing these salamanders. Further research is needed to tease out what factors maybe stressful.

Bio:  Megan J. Mondelli graduated from Rowan University (New Jersey) in 2013 earning a B.S. in Biological Sciences. During her undergraduate degree in 2012, she received a National Science Foundation funded REU position to explore population distributions and prey type of Plethodontid salamanders in New Hampshire. After, graduating, she worked for Rutgers University at Haskin Shellfish Research Laboratory participating in an oyster stock assessment survey for the Delaware Bay. In 2014, Megan began pursuing a M.S. in Population and Conservation Biology at Texas State University, studying how urbanization affects the seasonal variation in hormones and behavior and how runoff from storms affects hormones of Texas Eurycea salamanders.



Thesis Defense


Patch Occupancy and Population Density of the Crevice Spiny Lizard (Sceloporus poinsettii) in the Central Mineral Region of Texas


Name: Jeffrey T. Jenkerson

Major Advisor: Thomas R. Simpson, Department of Biology, Texas State University        

Committee Members: Ivan Arellano-Castro, Department of Biology, Texas State University, James F. Gallagher, Texas Parks & Wildlife


April 4, 2016, 1:00 PM, Supple 153

Herpetofaunal species within a landscape are strongly associated with the amount and availability of suitable habitat as defined by numerous characteristics of the microhabitat. I estimated occupancy and density of crevice spiny lizards (Sceloporus poinsettii) on monadnock features present on Mason Mountain Wildlife Management Area within the Llano Uplift area of the Central Mineral Region of Texas. From June to September 2015, I captured and marked 46 adult crevice spiny lizards using ®Floytag T-bar anchor tags. Average lizard density across sites was 1.41/100 m2 (SE = 0.023, n = 46).  Additionally, 382 lizards were detected across 20 locally isolated granitic outcrops during abundance sight surveys. These estimates were used to evaluate the relative influences of microhabitat variables on the distribution of this rock-dwelling lizard species within the context of habitat size and a landscape level variable (burning treatment). I measured variables that are either known or suspected to influence habitat suitability, including fine-scale rock habitat (i.e. ground cover, geology, amount of refuge and vertical surface area) and the landscape context (burning treatment). Multimodel information-theoretic approach suggests that at a local rock scale, crevice spiny lizard occupancy may be more closely related to refuge quality. At a boundary habitat scale, most parsimonious models suggest that geographic aspect is most influential to occupancy. These results indicate that patterns of occurrence may be tied closely to characteristics most immediately affecting the ability to thermo-regulate and find cover. Lizard density decreased with increasing site size, indicating that habitat size may not be positively correlated with habitat suitability for the crevice spiny lizard.

Bio:  Jeffrey T. Jenkerson graduated from the University of Texas at San Antonio in 2013 earning a B.S. in Biology with a concentration in Ecology. In 2014, Jeffrey began pursuing a M.S. in Wildlife Ecology at Texas State University, studying how habitat parameters affect crevice spiny lizard demography.

Thesis Defense

Inducing Biofilm Dispersion

Name: Sara Robertson

Major Advisor:    Dr. McLean          


Committee Members: Dr. Forstner and Dr. Rodriguez   


Monday, April 4, 2016  9am Supple Norris Room

Bacterial growth on surfaces results in these organisms forming a complex surface-adherent biofilm community. Growth as biofilms results in  microorganisms becoming highly resistant to most antibiotics and disinfectants. In this study I explore an alternative method for biofilm control by inducing dispersion of sessile organisms into an unattached (planktonic) growth mode using boric acid. Samples used were naturally-occurring aquatic biofilms from gravel in the San Marcos River. Biofilm concentrations and detachment due to exposure to boric acid (experimental) or water (control) was measured using dilution plating and growth on R2A agar. The study further explored the effects of dispersion by examining if a preferential release of certain bacterial taxa is induced. To determine whether boric acid induced a preferential removal of bacterial populations from aquatic biofilms, DNA was purified from biofilm samples prior to and following treatment with either boric acid or water, as well as from bacteria released through these two treatments. Using Illumina Miseq sequencing, community profiles of bacterial populations were obtained and showed the population released by boric acid treatment was similar to the original biofilm population. In contrast, the population released by water treatment showed a preferential release of microbes among taxa. Future implication for dispersion could be useful in food processing equipment, medical equip and long term goals of rejuvenation of older antibiotics.

Bio: Sara is from Georgetown TX. After high school she served 4 years active duty in the U.S. Navy and an additional 3 years as an active service reservist. After completing her active duty tour she studied wildlife and fisheries at Texas A &M and received a B.S in 2009. Sara then started her Master in the fall of 2014 and will be graduating May 2016 with a M. S. in Biology. 

Thesis Defense

Social factors during foraging bouts influence sexual segregation

Leah Peterson

Major Advisor: Dr. Floyd. W. Weckerly            

Committee Members:  Dr. Mark A. Ricca, Dr. Tim H. Bonner

Friday, April 1, 2016, 1:00PM, Supple Science Building 257

Large ungulate spatial patterns occurring at broad scales can often be explained by fine-scale processes that function at the individual level. To better understand broad-scale sexual segregation, fine-scale processes were examined in a non-migratory population of Roosevelt elk (Cervus elaphus roosevelti) in the Redwood National and State Parks, California, USA. Throughout twenty years of observation, this population exhibited a change in sexual segregation, allowing the opportunity to assess the potential influence of two fine-scale mechanisms: the availability of forage abundance and social factors during the forage bout. Per capita forage availability was estimated for comparison between two meadow complexes (2005-2016) to determine if selectivity for one meadow complex by males (and thus sexual segregation) could be explained by the greater absolute metabolic requirements in males. To assess the influence of social factors (such as group size, group type, or proximity of conspecifics) during the foraging bouts, focal observations were collected from adult male and female elk from 2009-2016. These data were used to conduct AIC analyses to select the best fit models for predicting the distance traveled, the variance in turning angles, and the proportion of time the animal spends with its head out of the feeding position during a foraging bout. Interestingly, we found that the availability of forage biomass was likely not the driver for males and females using separate meadow complexes. This study instead found that males are more vigilant than females and are more likely to move farther and in direct paths to avoid proximity of conspecifics. Consequently, males will be more influenced by social factors while foraging than females. The asynchronous responses to social factors by males and females may explain the exclusive, male-only use of a meadow complex from which females were recently extirpated. We can therefore conclude that sexual segregation is driven, in part, by fine-scale foraging behaviors.

Bio: Leah Peterson is originally from Des Moines, IA. She attended Creighton University in Omaha, NE and achieved her B.S. in Biology in 2013. Leah began her Wildlife Ecology Master’s program at Texas State in the fall of 2014 and with her M.S. degree, she hopes to pursue a career in wildlife research or consultation.

Thesis Defense

Density-Dependent not -Independent Factors Influence Roosevelt Elk Recruitment in the Bald Hills of Redwood National Park

Nicholas R. Kolbe

Major Advisor: Dr. Floyd. W. Weckerly            

Committee Members:  Dr. Thomas R. Simpson, Dr. Mark A. Ricca

Friday, April 1, 2016, 9:00 AM, Supple Science Building 257

Density-dependent and ­­-independent factors are known to influence population dynamics of large ungulates like Roosevelt elk (Cervus elaphus roosevelti). But the strength of influence of both kinds of factors depends on abundance relative to K carrying capacity. I examined the influence of density, climatic variables and prescribed fire on juvenile recruitment in an elk population in Redwood National Park, California, USA, from 2002 to 2015. In the Park prescribed fire is used to reduce conifer and redwood (Sequoia sempervirens) encroachment into meadows and is not used to manage elk habitat. Consequently, prescribed fire might have a density-independent influence on juvenile recruitment and population dynamics. Fire is also known to increase elk food supplies but whether fire might have a positive influence on recruitment depends on the population size relative to K. Between 2002 and 2015 abundance varied from 190 to 279. Using a Gompertz state-space model and expectation from the standard logistic model I estimated K to be between 275 and 340. An Akaike Information Criterion model selection analysis of 35 linear regressions estimating juvenile recruitment considered abundance, prescribed fire, and climatic influences. Population abundance alone had the strongest influence on juvenile recruitment. Our findings may be affected by the population being below K carrying capacity. Prescribed fire might not have influenced recruitment because the population was too far below K or an insufficient area was burned to substantially increase elk food supplies.

Bio: Nicholas Kolbe is from McQueeney, Texas. He graduated from Texas A&M University of Kingsville in Kingsville, TX with a B.S. in Range and Wildlife Management. Nicholas began his Masters of Science in Wildlife Ecology at Texas State University in the fall semester, 2014. While at Texas State, he has presented two papers at the Texas Chapter of the Wildlife Society annual meetings and published a manuscript in California Fish and Game. During the summer of 2015, he worked as an intern for Texas Parks and Wildlife Department at the Gus Engeling Wildlife Management Area, Tennessee Colony, TX. Nicholas has also received numerous scholarships from Texas State and non-governmental organizations.

Thesis Defense

The ecology of colonial nesting Green Herons (Butorides virescens) in Texas

Name: Nathan Trimble

Major Advisor:   Dr. M. Clay Green           

Committee Members:   Dr. David Huffman, Dr. Floyd Weckerly


Wednesday, March 30, 2016, 2PM, Norris Room

Green Herons (Butorides virescens) are small herons found throughout the eastern United States, the west coast of the United States and throughout most of the state of Texas. While this species can be found along the Texas Coast year round, they occur in greater densities during the breeding season. Green Herons are solitary foragers and often nest singly, with a breeding pair defending a breeding territory. Green Herons sometimes form loose breeding aggregations or colonies presumably as a function of habitat availability and/or predator pressure. A colony of at least 35 breeding pairs of Green Herons annually breed along a tidal creek in Port Lavaca, Texas. This study sought to determine a relationship between nest density and nest success and to use observational data to examine factors of this poorly understood behavior in Green Herons. A secondary goal of the study was to examine juvenile dispersal by banding chicks and monitoring adults in subsequent years to test whether juveniles return to their natal colony to breed. Nearest neighbor spacing varied from < 1 m to 42.5 m apart (mean=9.57m). All nests occurred in low shrubs Marsh Elder (Iva frutescens) along the water’s edge. Nesting began in early April and ceased in late July/early August. Clutch size ranged from 1-5 eggs for both years with a mean of 3.09 (SE=0.106) and 3.43 (SE=0.163) for 2014 and 2015 respectively. Nest success varied between years (2014, 53.57% nest success; 2015, 12.25% nest success); high nest mortality in 2015 was likely due to extreme weather events and human disturbance. AIC model selection favored models containing the quadratic effect of nearest neighbor estimate, Julian lay date, and year suggesting the possibility of an optimum nearest neighbor distance of around 12m for Green Herons at this location, though more years of data will be needed to reveal a strong trend given the high amount of density independent mortality in 2015. No chicks banded in 2014 were re-sighted in 2015.

 Nathan Trimble grew up in Houston, TX. He received a Bachelor’s of Science in Wildlife Biology from Lees-McRae College in Banner Elk, NC. Nathan got hooked studying birds in the mountains of North Carolina and joined the Wildlife Ecology program at Texas State University in fall of 2013 with a focus on avian ecology.

Thesis Defense

Using nutrients, sediment, ions, isotopes, and hydrograph separation to quantify conduit-dominated recharge processes in a Trinity Aquifer site: Cave Without a Name

Michael Markowski

Major Advisor: Dr. Benjamin Schwartz     

Committee Members: Dr. Weston Nowlin, Dr. Astrid Schwalb

Wednesday, March 30, 8:30 AM, Freeman Aquatic Building 130 (FAB 130)

Cave streams provide an ideal location for sampling waters transported through a karst system because they integrate basin-wide sources ranging from fast flow in conduits to slow flow through the bedrock matrix. Although numerous studies have monitored cave streams to characterize these process, most have infrequent sampling intervals and/or a limited number of measured parameters. This study used a large dataset that includes high frequency sampling and comprehensive stormwater analyses of surface and cave stream water from five storm events between July 2014 and July 2015 at Cave Without A Name (CWAN) in central Texas.  The objectives were to determine which environmental factors influence the timing and proportions of storm water and pre-event water moving through the system and to quantify relationships between discharge and sediment, nutrient, and ion concentrations within and across storm events. Results show that evapotranspiration (summed over prior 12 weeks to each storm), soil moisture (at 10-40cm), and cave-stream discharge prior to each storm affects the timing of the peak ratio of stormwater/pre-event water flow through the cave. As antecedent conditions became wetter from July 2014 to July 2015, peak stormwater arrival times dropped from days to hours. Progressively faster stormwater arrival times, heterogeneity within and across storm chemographs and sediment graphs, and water isotope data all indicate a flushing of the upper unsaturated zone during Events 1 and 2, and progressive wetting of unsaturated portions of the system from July 2014 to July 2015. Taken together, these data reveal complex hydrologic and mass transport dynamics, variable rainfall-runoff and rainfall-recharge relationships, and highlight that a single storm cannot be used to accurately describe how a karstic groundwater system responds to storm events under a wide range of hydrologic conditions.  This better understanding of recharge processes at CWAN will help guide future research and surface water/groundwater management in karst regions.

Bio:  Michael Markowski attended The University of Texas and received a B.S. in Hydrogeology in 2010. He spent two years at the Pickle Research Campus, where he worked with both fluvial geomorphology and glaciology teams. He plans on completing his M.S. in Aquatic Resources from Texas State University this May.

Dissertation Defense


Influence of Brain-Derived Neurotrophic Factor and Family History of Alcohol Dependence on Alcohol USE IN Healthy Social Drinkers

Shobhit Sharma

Major Advisor: Dr. Natalie Ceballos

Committee Members: Dr. Dana Garcia, Dr. Brett Ginsburg, Dr. Michelle Lane and Dr. Shannon Weigum


Monday, March 28, 12:00 Noon, Supple Science Building Norris conference room

Brain-derived neurotrophic factor (BDNF) is important for neuronal survival, differentiation and consolidation of synaptic strength. Studies have found increased alcohol use and genetic risk for alcohol dependence in individuals with the Val66Met single-nucleotide polymorphism (SNP) of the BDNF gene, a genotype associated with decreased activity-dependent release of BDNF. However, the literature remains contentious with regard to this issue. The current study was designed to address this issue with two aims. Aim 1 examined the influence of the Val66Met SNP, serum BDNF levels, and family history of alcohol dependence (FH) on alcohol use in healthy social drinkers. It was expected that the Val66Met polymorphism would be associated with higher drinking levels compared to the Val66Val genotype, and those participants with a combination of Val66Met genotype and a positive FH would exhibit the most severe alcohol use profile. Results for Aim 1 indicated no significant effects of genotype on quantity/frequency of alcohol use; however, the Val66Met group had an earlier age at first alcohol use. FH-positive participants had an earlier age at first drunken episode. There were no interactions of BDNF genotype x FH group. Correlational analyses revealed that quantity/frequency of alcohol use was positively related to perceived stress levels in the Val66Met group, such that participants with higher stress levels tended to consume more alcohol. This relationships was not present in the Val66Val group. Aim 2 examined stress-related changes in serum BDNF levels. It was expected that Val66Met and Val66Val groups would have different stress-related changes in serum BDNF levels, and that the profile of the Val66Met group would be associated with more severe alcohol use. Results of Aim 2 indicated that, across groups, serum BDNF levels decreased in response to stress, but there were no main effects or interactions of BDNF genotype or FH group. However, in the Val66Met group, stress-related BDNF change (post- minus pre-stress) was related to age at first drink, such that earlier age of alcohol use was associated with a greater stress-related decrease in serum BDNF. This relationship was not present in the Val66Val group. Taken together, the results of these two aims suggest that in healthy young social drinkers, the association between the Val66Met SNP and alcohol use may be linked to stress vulnerability and behavioral risk factors (i.e., earlier initiation of alcohol use), which are known to be associated with the development of alcohol dependence.

BIO: Shobhit Sharma received his MS in Biology from Texas State in Spring 2011. He entered Aquatic Resources Ph.D. program in Fall 2011. As an instructional assistant he has taught laboratory courses in Anatomy & Physiology and Clinical Lab Science. During his PhD he received grant from The Texas Research Society on Alcoholism (TRSA).

Thesis Defense

Grazing Influence on Selected Parameters of the Avian Community on a Texas Hill Country Ranch

Joseph A. Jandle

Major Advisor: Dr. Thomas R. Simpson, Department of Biology, Texas State University             

Committee Members: Dr. Michael R. J. Forstner, Department of Biology, Texas State University

Dr. M. Clay Green, Department of Biology, Texas State University


Monday, March 28, 2016, 9:00 AM, Supple 153

Many regionally declining prairie and shrubland birds breed in the Edwards Plateau ecoregion of Central Texas.  Additionally, Central Texas supports a winter resident bird community rich in ground foraging sparrow species.  Livestock grazing can have species specific and mixed results for local bird communities and other wildlife.  I examined the degree to which grazing influences bird foraging frequency and the overall bird community relative to herbaceous ground cover at Freeman Center, a 1,701 ha working cattle ranch in the Balcones Canyonlands subregion of the Edwards Plateau.  For one year, I conducted avian surveys and herbaceous ground cover surveys on two grazed and two ungrazed pastures using twenty, 100 meter fixed radius point count sites and twenty, 100 meter transects extending from each site.  I included a total of 383 line transect Daubenmire surveys, 135 point count surveys, and 184 avian walking transect surveys in various analyses.  I used GLMs to analyze herbaceous ground cover surveys in grazed and ungrazed sites.  I incorporated significant herbaceous predictors into GLMMs to analyze breeding and winter resident abundance, richness, diversity, and evenness.  I also included site as a random factor.  I built an additional GLMM to analyze avian winter ground foraging counts.  I identified a total of 138 avian species from Freeman Center between January 2014 and May 2015.  All breeding bird indices were significantly different between years.  Breeding bird richness positively correlated with forb cover (P = 0.003).  Breeding bird diversity was positively correlated with tallest green grass (P = 0.016) and forb cover (P = 0.007).  Except foraging counts, no winter resident indices were significantly correlated with herbaceous ground cover predictors.  Winter resident foraging counts were positively correlated with forb cover (P = 0.002).  Breeding and wintering bird abundance, richness, diversity, and ground foraging counts were higher in grazed sites than ungrazed sites.  Results suggest that moderate rotational grazing promotes forb production and native forbs are important for breeding and wintering birds in the Texas hill country.  Future study should determine herbaceous diversity and the dominant herbaceous plants in a study area.  Judgment deferred rotational grazing should be appropriate when ranch managers have the knowledge, experience, and prudence to make best-management decisions based on climate, rainfall, and sustainability.  A Multi-year study is necessary to assess long-term cattle use and the affects of climate and rainfall on the health and future of ranch operations and wildlife at Freeman Center.

Bio: Joseph A. Jandle was born in San Marcos, Texas. He earned a B.S. from Texas State University in 2011 with a major in Wildlife Biology.  He entered the Wildlife Ecology Master’s program at Texas State University in 2014. He studies avian ecology with an emphasis on identification, vocalization, and rangeland species in Dr. Simpson’s lab.

Thesis Defense

Geochemical clues to groundwater sources of the Pedernales River

Sarah J. (Saj) Zappitello

Major Advisor: Dr. Benjamin Schwartz            

Committee Members:  Dr. Thomas Hardy, Dr. Alan Groeger

Wednesday, March 23, 1:00PM, Freeman Aquatic Building 130

Interactions between aquifers and rivers are recognized as important components of the hydrologic system. Central Texas rivers and aquifers are especially well connected due to karstic carbonate geology where gaining and losing streams, springs, and caves are common. The Pedernales River is an important source of water for local communities, the city of Austin, and downstream water users of the Colorado River, to which it drains. The Pedernales River Basin is surrounded by rapidly developing areas with increasing water demands, but the majority of the watershed is developed only for agriculture. Identifying critical areas for water quality and quantity protection while the land is still relatively undeveloped creates an opportunity for proactive water resource protection. This study compares the geochemistry of waters from the main stem and tributaries to the Pedernales River, springs across the basin, wells screened in specific aquifers, and historic data. By conducting this study during baseflow conditions, the water sources are assumed to originate exclusively from groundwater, as opposed to runoff or soil interflow. Geospatial information was also evaluated for river gains and losses where measured, springs, and surface geology. Stable isotope ratios and principal component analysis highlight the importance of groundwater contributions to the river and indicate that evaporation is controlling the geochemical evolution of surface waters. Human impacts are also illustrated by spatial analysis of water geochemistry.

Bio: Saj Zappitello is from Dripping Springs, Texas. She graduated from the University of Texas at Austin in 2006 with a B.S. in Hydrogeology and Environmental Geology. Saj is a professional geologist and an endangered karst invertebrate specialist, and she worked in environmental consulting on karst issues in the Edwards Aquifer before starting her Masters of Science in Aquatic Resources at Texas State University in the fall semester of 2014. She is an avid cave explorer and tuba player. Saj lives in south Austin with her husband, two ferrets, and ten chickens.

Thesis Defense

Inhibition of quorum signaling in Chromobacterium violaceum in the presence of cadmium, cobalt and nickel divalent cations

Name: Starla Thornhill

Major Advisor:   Dr. Robert JC McLean 


Committee Members: Dr. Leticia Vega, Jacobs International (NASA JSC);   

                                Dr. Kavita Kakirde, Texas State University


Tuesday, March 22, 2016, 11 AM, Norris Room

Bacteria are single celled organisms capable of acting as a single unit by sensing and responding to population density via a phenomenon called quorum signaling. Quorum signaling regulates a variety of phenotypes including biofilm formation and virulence factor production. In the soil bacterium Chromobacterium violaceum the virulence factor violacein results in a deep purple pigmentation and is one such regulated phenotype. Previously, a number of biological and organic molecules have been described as quorum signaling inhibitors, but to date no metal-based inhibitors have been identified. In this study, we show that quorum sensing is inhibited in C. violaceum when in the presence of sub-lethal concentrations of cadmium based salts. Cobalt and nickel salts have also been indicated as inhibitors in other gram negative species. Inhibitory effects of cadmium divalent cations on C. violaceum were shown in biofilm formation, pigmentation and virulence factor production, as well as transcript levels for genes involved in these processes. This study represents the first description of heavy metal based quorum sensing inhibition in C. violaceum.

 Starla Thornhill graduated from Texas State University with a B.S. in Microbiology in May 2014. Her research interest is in bacterial growth in the microgravity environment, and she has spent time at NASA Johnson Space Center training in use of microgravity simulating bioreactors. 

Dissertation Proposal Defense

The Arabidopsis Mediator Complex Subunit 9, a MORC1 interacting protein, is a positive regulator of plant immunity

Ji-Chul Nam

Major Advisor: Dr. Hong-Gu Kang, Department of Biology, Texas State University             

Committee Members: Dr. Nihal Dharmasiri, Department of Biology, Texas State University

Dr. Sunethra Dharmasiri, Department of Biology, Texas State University

Dr. Walter Gassmann, Division of Plant Sciences, University of Missouri

Dr. Keiko Yoshioka, Department of Cell & Systems Biology, University of Toronto

Tuesday, March 1, 2016, 2:00 pm, 209 Undergraduate Academic Center

Arabidopsis thaliana MORC1 (Microrchidia), also known as CRT1, is an ATPase protein that is required for multiple levels of plant immunity including effector-triggered immunity (ETI), PAMP (pathogen-associated molecular pattern)-triggered immunity (PTI), basal resistance, non-host resistance, and systemic acquired resistance. Consistent with its role in ETI and PTI, MORC1 physically interacts with 11 resistance proteins and the PAMP-recognition receptor FLS2. We employed yeast two-hybrid to assess a protein-interaction profile of MORC1 and identified 14 MORC1-interacting proteins (MIPs). To characterize the role of MIPs in plant immunity, we obtained T-DNA insertion lines for some MIPs and generated combined mutants with morc1/morc2. Five out of eight mip mutants tested exhibited decreased resistance against Pseudomonas syringae, suggesting that these MIPs function in plant immunity. For instance, mip13 displayed compromised resistance to P. syringae while overexpression of MIP13 conferred enhanced antibacterial resistance. Interestingly, addition of the morc1/2 mutation restored resistance to P. syringae in mip13, suggesting a complicated interaction between MIP13 and MORC1/2 in plant immunity. MIP13 encodes MED9, a component in plant RNA polymerase II mediator complex and likely functions in the transcriptional induction of defense genes. Thus, we are currently assessing the transcriptional induction of selected defense genes in MIP13 altered backgrounds in conjunction with morc1/2 to learn how MIP13 and MORC1/2 interplay in plant defense responses.

Bio: Nam Ji-Chul was born in Seoul, South Korea. He earned a B.S. from the University of Missouri in 2010 with a major in Biological Sciences. He earned a M.S. from the University of Missouri in 2013 in Plant Sciences from Dr. Gassmann. He entered the Aquatic Resources Ph.D. program at Texas State University in 2013. He studies molecular plant immunity with an emphasis on the transcriptional control of disease resistance genes in Dr. Kang’s lab.


Dissertation Proposal Defense

Natural History, Demographic Parameter Estimates, and Survey Techniques for Federally Threatened Jollyville Plateau Salamanders (Eurycea tonkawae)


Zachary C. Adcock

Major Advisor: Dr. Michael Forstner, Department of Biology, Texas State University             

Committee Members: Dr. David Rodriguez, Department of Biology, Texas State University

Dr. Benjamin Schwartz, Department of Biology, Texas State University

Dr. Benjamin Pierce, Department of Biology, Southwestern University

Dr. James Nichols, U.S. Geological Survey

Tuesday, January 19, 2016, 3:00 pm Norris Room

The central Texas Eurycea salamanders are of high conservation concern because of their extreme level of endemism, small ranges, and the rapid urbanization of the greater Austin and San Antonio areas. Seven of the 13 currently recognized species are listed as either threatened or endangered by the U.S. Fish and Wildlife Service (USFWS), and three additional species are listed as threatened or endangered by the Texas Parks and Wildlife Department (TPWD). Eurycea tonkawae was federally listed as threatened in 2013, and despite the increased attention from the listing process, few publications exist that advise conservation decisions for this taxon. The USFWS relied heavily on unpublished data for the listing decision and for establishing critical habitat units. Effective design and implementation of conservation policy is not possible without adequate natural history knowledge of the target species. In this dissertation, I intend to address several issues important to the conservation of E. tonkawae, including: 1) delineating the full extent of occupied surface habitat, 2) identifying small-scale environmental variables that influence presence (microhabitat parameters), 3) describing annual ecology, 4) estimating demographic parameters (e.g., abundance, survival), and 5) investigating environmental DNA (eDNA) as a survey technique. This work will contribute to informed conservation policy and management decisions for the recovery of Eurycea tonkawae.

Bio: Zach Adcock was born in Andrews, TX and raised in Cedar Hill, TX. He earned a B.S. from the University of Tampa in 2004 with a double major in Biology and Environmental Science and a double minor in Marine Biology and Chemistry. He earned a M.S. from the University of South Florida in 2012 in Integrative Biology from Drs. Henry Mushinsky and Earl McCoy’s lab. He worked as a wildlife and wetland consultant in Florida for 10 years concurrent with and in-between the two degrees. He entered the Aquatic Resources Ph.D. program at Texas State University in 2012, in Dr. Michael Forstner’s lab, to continue work on the conservation of endangered and threatened wildlife. His fiancée, Michelle Curtis, is in the Wildlife Ecology program at Texas State University and they have one son, Davis, of whom they are very proud.

Fall 2015

Proposal Defense

Characterization of chromatin-remodeling factors in plant immunity

April Bonnard

Major Advisor: Dr. Hong-Gu Kang            

Committee Members: Dr. Nihal Dharmasiri & Dr. Suni Dharmasiri

Tuesday, December 8, 2015, 2:00PM, Norris Room, Supple Building

Abstract: Plants have evolved a complex immune system against various pathogens, part of which involves the function of resistance (R) proteins in detecting the presence of secreted effector molecules from pathogens. This detection then leads to a robust immune response by implementing large-scale modifications in chromatin accessibility, thus leading to transcriptional reprogramming. MORC1 is a protein that interacts with several of these R-proteins and is required to maintain optimum levels of immunity in Arabidopsis thaliana. It is speculated that MORC1 is a putative chromatin-remodeling factor as it has been shown to exhibit ATPase and endonuclease activity and that a subpopulation localizes to the nucleus after pathogen infection. In this research, we aim to characterize the interaction of MORC1 with several other chromatin-remodeling factors, including ACT1, ARP4, SWC2, SWC5, SWC6, SUF3, PIE1, RVB1, and YAF9, which together comprise many of the components of the SWR1-like complex in Arabidopsis to better understand the role of MORC1 as well as the link between chromatin-remodeling and plant immunity.

Bio: April Bonnard graduated from Texas State University in 2014 earning a B.S. in Biology with a minor in Biochemistry. She is now pursuing her M.S. in Biology at Texas State University where she is studying the relationship between chromatin-remodeling and plant immunity. During her time in the M.S. program, she became a member of the Alpha Chi National College Honor Society and participated in the 20th Annual Department of Biology Colloquium, where she received an award for the best talk at the M.S. level.

Proposal Defense


Michele Crawford-Reynolds

Major Advisor: Dr. Thom Hardy, Department of Biology, Texas State University    


Committee Members: Dr. Paula Williamson, Department of Biology, Texas State University

Dr. Weston Nowlin, Department of Biology, Texas State University                                                

Dr. David Lemke, Department of Biology, Texas State University

Dr. Tina Cade, Department of Agriculture, Texas State University

Dr. Robert Doyle, Department of Biology, Baylor University         

Thursday, December 3, 2015, 9:00 AM, Freeman Aquatic Building, Room 130

 Texas wild rice (TWR), Zizania texana, is a submerged macrophyte with a single known population existing in the upper reaches of the San Marcos River.  Historically, this rare aquatic grass was in greater abundance than is observed today. First listed as a federally endangered species by the U.S. Fish and Wildlife Service in 1978 priority has since then been placed on the recovery and sustainability of TWR.  Anthropogenic factors have been suggested to continue to present challenges for the re-introduction and maintenance of TWR. Previous research has focused on habitat suitability preferences for TWR with research still lacking in understanding all the factors that may limit its potential to recover to historical levels. Suspended sediment induced turbidity due to contact recreational use of the river is one such anthropogenic factor suggested to be problematic. Turbidity has been correlated with causing a decrease in the availability of photosynthetically active radiation (PAR) in aquatic systems. The goal of this study is to evaluate the impact suspended sediment induced turbidity and subsequent reduction in PAR has on the vegetative growth and biomass productivity of TWR.  The experimental design will involve both in situ and ex situ observations, seasonal aspects (temporal) and recreational use (low and high). Identifying the impact recreational induced turbidity has on the vegetative growth of TWR may provide additional information useful in future conservation and restoration effort.

 Michele Crawford-Reynolds graduated from University of The Incarnate Word in 1991 earning a bachelor’s in biology. She later earned a master’s degree from UIW in biology (’93) and in education from Sul Ross University (’98). She has taught at a community college in the biology department since 1995. She has two children, a daughter majoring in biology at Texas A&M University in College Station and a son majoring in psychology attending Austin Community College.

Proposal Defense



Michele Crawford-Reynolds

Major Advisor: Dr. Thom Hardy, Department of Biology, Texas State University              

Committee Members: Dr. Paula Williamson, Department of Biology, Texas State University

Dr. Weston Nowlin, Department of Biology, Texas State University

Dr. David Lemke, Department of Biology, Texas State University

Dr. Tina Cade, Department of Agriculture, Texas State University

Dr. Robert Doyle, Department of Biology, Baylor University


Thursday, November 19, 2015, 8:30 AM, Freeman Aquatic Building, Room 130

 Texas wild rice (TWR), Zizania texana, is a submerged macrophyte with a single known population existing in the upper reaches of the San Marcos River.  Historically, this rare aquatic grass was in greater abundance than is observed today. First listed as a federally endangered species by the U.S. Fish and Wildlife Service in 1978 priority has since then been placed on the recovery and sustainability of TWR.  Anthropogenic factors have been suggested to continue to present challenges for the re-introduction and maintenance of TWR. Previous research has focused on habitat suitability preferences for TWR with research still lacking in understanding all the factors that may limit its potential to recover to historical levels. Suspended sediment induced turbidity due to contact recreational use of the river is one such anthropogenic factor suggested to be problematic. Turbidity has been correlated with causing a decrease in the availability of photosynthetically active radiation (PAR) in aquatic systems. The goal of this study is to evaluate the impact suspended sediment induced turbidity and subsequent reduction in PAR has on the vegetative growth and biomass productivity of TWR.  The experimental design will involve both in situ and ex situ observations, seasonal aspects (temporal) and recreational use (low and high). Identifying the impact recreational induced turbidity has on the vegetative growth of TWR may provide additional information useful in future conservation and restoration effort.

Michele Crawford-Reynolds graduated from University of The Incarnate Word in 1991 earning a bachelor’s in biology. She later earned a master’s degree from UIW in biology (’93) and in education from Sul Ross University (’98). She has taught at a community college in the biology department since 1995. She has two children, a daughter majoring in biology at Texas A&M University in College Station and a son majoring in psychology attending Austin Community College.


Thesis Defense



Damian T. Raymond

Major Advisor: Dr. Nihal Dharmasiri     

Committee Members: Dr. Sunethra Dharmasiri and Dr. Hong-Gu Kang


Monday, Nov 9, 2015,  8:30 am in Supple 257

The Major facilitator superfamily (MFS) transporter proteins regulate solute homeostasis across membranes in both prokaryotes and eukaryotes. Recently we isolated several mutant alleles of Arabidopsis PIC30, which encodes an MFS transporter protein that transports nitrate (NO3-) and synthetic auxin, picloram. Arabidopsis genome also consists of a gene, PIC30H (PIC30 homolog), which shows higher sequence homology to PIC30. In silico analysis indicate that both PIC30 and PIC30H consist of an MSF domain and a Noduline like (NOD) domain. Therefore, we hypothesized that PIC30H may function redundantly with PIC30. Using genetic and biochemical approaches we found that PIC30H localizes to plasmamembrane similar to PIC30. Nevertheless, tissue specific expression of these two genes indicates reasonable differences in spatial expression.  Furthermore, overexpression of PIC30H in pic30 did not rescue the picloram resistant root growth of pic30 suggesting that these two genes may not function redundantly. Arabidopsis mutants of both PIC30 (pic30) and PIC30H (pic30HKO) were resistant NO3- analog ClO3- suggesting both PIC30 and PIC30H transport NO3- inwardly. Interestingly, dark-induced hypocotyl growth of pic30HKO was hypersensitive to picloram while the hypocotyls of pic30 mutant was resistant when compared with wild type suggesting that PIC30 and PIC30H may transport picloram in an opposite direction. Taken together these results indicate that while some transport functions of PIC30 and PIC30H are similar, they may also have different transporter functions despite their sequence similarity.

Bio:  Damian T. Raymond graduated from University of Peradeniya – Sri Lanka in 2011 earning a B.S. in Botany with a minor in Chemistry.  In 2013, he began pursuing a M.S. in Biology at Texas State University, characterizing a putative picloram transporter protein in Arabidopsis.

Thesis Defense

Rumenreticulum - Liver Masses Relationship in White-tailed deer (Odocoileus virginianus) differ between males and females

Gayatri Bhaskar

Major Advisor: Dr. Floyd. W. Weckerly            

Committee Members:  Dr. Thomas R. Simpson, Dr. M. Clay Green.

Wednesday, November 11th, 8:00AM, Supple Science Building 153

Relationships between organ masses probably influence energy demands in mammals. Previous studies have estimated allometric relationships between body mass and organ masses in white-tailed deer. To my knowledge, however, there has been no investigation into the relationship between rumen-reticulum organ mass and liver mass in any ungulate. Furthermore, energetically demanding life history events like lactation in females and mating in males should affect organ workloads. Understanding the co-dependent relationships of these organs could be insightful to understanding the energy conservation strategy of white-tailed deer. I examined relationships between rumen-reticulum organ and liver masses in white-tailed deer to see if relationships differed between females and males during and two months before the mating season. I collected 151 white-tailed deer (68 males and 83 females) from Kerr pens, Central Texas, and a private ranch in South Texas (SOTX). Deer from the Kerr pens were obtained during the peak of the mating season, whereas deer from SOTX were collected two months prior to the mating season. All females had also given birth to young in the previous spring or summer. There was a positive relationship between masses of the rumen-reticulum organ and liver at both study areas. However, this relationship differed between males and females. In comparison to females, males exhibited heavier livers in relation to rumen-reticulum organ masses at both study areas. These findings might be useful to understanding physiological changes during energetically demanding periods in male and female white-tailed deer.

Bio: Gayatri Bhaskar is from Bangalore, India. She attended Western Kentucky University at Bowling Green, KY for her B.S in Biology. Gayatri began the Masters of Science in Wildlife Ecology at Texas State University in spring semester, 2014. While at Texas State, she presented a paper on “Birth mass scaling in Elk (Cervus elaphus)” at the 51st Texas Chapter of the Wildlife Society annual meeting, Corpus Christi, Texas. During the summer of 2015, she worked as an intern for Texas Parks and Wildlife at Kerr Wildlife Management Area, Hunt, TX.

Thesis Defense


Urbanization and Stress Response of Texas Eurycea Salamanders

 Name: Megan J. Mondelli

Major Advisor: Caitlin R. Gabor, Department of Biology, Texas State University 


Committee Members: Chris Nice, Department of Biology, Texas State University

Andrew Gluesenkamp, Texas Parks & Wildlife

Nathan Bendik, Watershed Department, City of Austin


November 6, 2015, 8AM, Norris Room

Amphibians worldwide are rapidly declining. Successful conservation strategies should consider the physiological response of an organism to its environment using stress hormones. Glucocorticoid (CG) hormones are a particularly useful class of biomarkers that effectively measure stress. The primary GC stress hormone in amphibians is corticosterone (CORT). Short-term increases in CORT (i.e., acute stress) are adaptive during stressful events because CORT mediate metabolic and immune function. However, chronic stress can be harmful to the overall health of an organism and can lead to dysregulation of the hypothalamic-pituitary-interrenal (HPI, for amphibians) axis leaving the organism susceptible to metabolic and immune problems. Chronic stress is also associated with suppressed reproductive hormones such as testosterone and estradiol. Anthropogenic and environmental factors such as seasonal changes, urbanization (modification, pollution) and storms have been shown to affect stress and reproductive hormones. Here, I studied how these factors affect the stress of two federally threatened species of Texas Eurycea salamanders that are fully aquatic. I conducted two projects, the first of which measured stress levels of E. tonkawae, Jollyville Plateau salamander, in urban and rural streams across seasons. I also examined the correlation between stress, sex steroids and activity levels of salamanders in urban and rural streams. My second project investigated the effects of storm water runoff on stress of E. nana, San Marcos salamander. I found that CORT in E. tonkawae is highest in summer but did not vary based on stream type. Activity in E. tonkawae varied by population; one urban stream showed a positive correlation between activity and CORT while but this was not the case in the other populations. However, urbanization did not affect activity level. Additionally, my research shows a significant effect of storm runoff water on testosterone, but not CORT in E. nana. In conclusion, my research shows that CORT changes with season and should be considered when testing other questions stress response. Additionally, it is possible that storm water does not affect the stress of salamanders, but some other factor associated with storm events might be stressing these salamanders. Further research is needed to tease out what factors maybe stressful.

Bio:  Megan J. Mondelli graduated from Rowan University (New Jersey) in 2013 earning a B.S. in Biological Sciences. During her undergraduate degree in 2012, she received a National Science Foundation funded REU position to explore population distributions and prey type of Plethodontid salamanders in New Hampshire. After, graduating, she worked for Rutgers University at Haskin Shellfish Research Laboratory participating in an oyster stock assessment survey for the Delaware Bay. In 2014, Megan began pursuing a M.S. in Population and Conservation Biology at Texas State University, studying how urbanization affects the seasonal variation in hormones and behavior and how runoff from storms affects hormones of Texas Eurycea salamanders.

Thesis Defense


OF THE REDDISH EGRET (Egretta rufescens)

Golya Shahrokhi

Major Advisor: Dr. M. Clay Green           

Committee Members:  Dr. David Rodriguez, Dr. Bart M. Ballard

Friday, October 30, 2015, 10:00 AM, Supple Building, Room 257

Reddish Egret (Egretta rufescens) is one of the least studied herons in North America. This dimorphic bird ranges from Baja California to Bahamas, north to Texas and Louisiana and southwards to Central America and northern part of South America. For this study we examined gene flow and genetic diversity among populations across the range of the species. We specifically tested the hypothesized distinct management units (Western, Central, Eastern) based on geographic distribution and the findings of Hill et al. (2012). We collected blood and feather samples from nestlings (n = 145) of 8 populations (Baja California, Chiapas, Yucatan, Tamaulipas, Texas, Louisiana, Florida and the Bahamas). We extracted DNA from collected samples and used 10 microsatellite markers and one mtDNA (control region) to estimate deviations from Hardy-Weinburg equilibrium, genetic differentiation, structure and gene flow. In all analysis we had more differentiations among groups and regions (Fst = 0.21) than among populations within groups (Fst = 0.09). Our results revealed three primary breeding concentration centers, one in each of the management units (Baja California for Western, Chiapas for Central, and Bahamas for Eastern) providing further support for the established management units. We found greater differentiation between populations in our mtDNA analysis suggesting less movement across populations and management units and greater philopatry in females in comparison to males. Differences in movement patterns between males and females is also supported by recent banding and telemetry data. Lastly, gene flow between the Baja California population and the remainder of species’ populations is weak whereas we detected weak to moderate gene flow between populations in Central and Eastern management units

Bio: Golya Shahrokhi received her Bachelor’s degree at Shahid Beheshti University (National University of Iran) in Biology with a minor in Zoology from Iran in 2012. She enrolled in the Wildlife Ecology Master program at Texas State University - San Marcos in 2013 and has started to work with Dr. M. Clay Green since then.  While her studies at Texas State, she won the Kushlan Research Award from Waterbird Society and Texas State University Graduate College Thesis Research Support Fellowship. Her poster, also, won the best student poster at Waterbird Society meeting in Bar Harbor, Maine in August 2015.

Thesis Defense

Characterization of an IBR5 interacting protein, ARA2 in Arabidopsis auxin response

Prabesh Ghimire

Major Advisor: Dr. Nihal Dharmasiri, Department of Biology, Texas State University         

Committee Members:  Dr. Hong-Gu Kang, Department of Biology, Texas State University

                                 Dr. Sunethra Dharmasiri, Department of Biology, Texas State University


October 29, 2015,  2.00 pm in Supple 257

         Auxin controls plant growth and development through both genomic and non-genomic processes. Genomic processes are regulated through the degradation of a group of transcriptional repressors called Aux/IAAs. Recent studies indicate that IBR5 (Indole-3-butyric acid response5), a dual specificity phosphatase, also regulates degradation of Aux/IAAs through an unknown mechanism. To better understand how IBR5 regulates plant auxin response, we recently carried out a yeast two hybrid screen to identify IBR5 interacting proteins. ARA2 was isolated as one of the putative IBR5 interacting proteins. ARA2, which is a small GTP binding protein, belongs to Ras super family of proteins that play essential roles in the intracellular transport pathways of yeast, mammalian cells, as well as in plant responses to various environmental stimuli. Several other small GTPases such as ROP2 and ROP6 are also known to be involved in plant auxin responses suggesting that small GTPases are integral components of auxin signaling. Thus, it was hypothesized that ARA2 play a role in plant auxin responses through interaction with IBR5. Results presented here show that ARA2 physically interacts with IBR5 both in-vitro and in vivo. This interaction occurs through the catalytic domain of IBR5. Interestingly, Aux/IAA degradation in loss-of-function ara2 mutant is affected suggesting that ARA2 may be a positive regulator of auxin responses. Nevertheless, ara2 mutant does not any show altered auxin related physiological responses probably due to genetic redundancy. However, characterization of ara2/ibr5-1 double mutant reveals that ara2 mutation functions as a mild enhancer of ibr5-1 especially in stress responses suggesting that ARA2 together with IBR5 may function in modulating the auxin responses during environmental stress.

Bio: Prabesh Ghimire was raised in Kathmandu, Nepal and received his BS degree in Biotechnology from Purbanchal University, Kathmandu in December 2011. Then he joined the Department of Biology, Texas State University to follow graduate studies in 2013. During his MS program, he worked both as a research assistant and an instructional assistant. In 2014, he was awarded the best poster presentation at the Biology Colloquium.

Thesis Defense



Greg A. Cummings

Major Advisor: Dr. Thomas B. Hardy     

Committee Members: Dr. Timothy H. Bonner, Dr. Adam J. Kaeser

October 27, 2:00 PM, The Meadows Center for Water and the Environment, (SLH 107)

Rainbow Trout Oncorhynchus Mykiss are typically stocked in tailraces across the southeastern United States to mitigate fish habitat and assemblage alterations caused by large impoundments.  Hypolimnetic discharges from Canyon Reservoir have created conditions suitable for a coldwater tailrace fishery and Rainbow Trout have been stocked there since 1966.  This study examined changes in suitability and availability of Rainbow Trout habitat with discharge rate to provide flow and stream restoration recommendations for the Canyon Reservoir tailrace.  Physical habitat modeling incorporated habitat suitability information for three life stages of trout coupled with hydraulic modeling to assess habitat quality and quantity at various flow rates.  Habitat mapping included traditional surveying, remote sensing, bathymetric mapping, and side scan sonar.  Side scan sonar was evaluated for efficiency and applicability to semi-wadable rivers.  Results indicate the tailrace is spawning limited and temperature, not habitat, is the primary limiting factor for adult trout.  Modified flow rates and specific stream restoration measures could increase adult trout abundance and assist put-grow-and-take strategies in the upper portion of the tailrace.  Side scan sonar provided efficient mapping of non-wadable sections of the study area.  However, there were limitations related to water level, access, navigability, positional accuracy, and post-processing.  Trial runs, training, map accuracy assessments, and further development with instruments and post-processing will improve this method in similar scenarios.

Bio:  Greg A. Cummings graduated from Oklahoma State University in 2003 earning a B.S. in Wildlife and Fisheries Ecology with a minor in Geography.  After graduating, he interned with a North Carolina State University graduate study investigating Striped Bass diet in the Albemarle Sound estuary.  Since 2004, he has worked for the Inland Fisheries Division of Texas Parks and Wildlife, managing public fisheries in Central Texas.  In 2010, he began pursuing a M.S. in Aquatic Resources at Texas State University, studying habitat mapping techniques and stream modeling.

Thesis Defense


Ionic Requirements of Blue Crab, Callinectes Sapidus, in Environments Containing Low Concentrations of Total Dissolved Solids

Duane A Friedman

Major Advisor: Dr. Joseph R. Tomasso                                 

Committee Members: Dr. Weston H Nowlin, Dr. Benjamin Schwartz


Friday, October 23, 2:00 pm, Freeman Aquatic Building, Room 130

The goal of this study was to develop an ionic environment containing 1 g/L total dissolved solids (TDS) that would support the survival and growth of juvenile blue crabs (designated a “mixed-ion solution”). The 1 g/L TDS level was selected in order to minimize the cost of preparing ponds and to potentially reduce the need for effluent permitting in inland areas. The general approach was to provide selected ions in approximate concentrations found in 1 g/L dilute seawater.

In a series of three-week exposures beginning with ~20 mm carapace-width crabs, we found:

  1. Growth in artificial sea-salt treatments of 1, 2, 4, and 8 g/L TDS averaged 76% ± 20.2% (mean ± SD) and was not significantly affected by treatments. The number of molts, feed intake and modified feed conversion ratio were not significantly affected by treatments.
  2. Growth during exposure to 1 g/L sea-salt, 0.5 g/L sea-salt + 0.5 g/L mixed-ions or 1 g/L mixed-ions averaged 41% ± 0.49% and was not significantly affected by treatment. Although not quantified, some exoskeletons in the mixed-ion treatment appeared soft and off-colored, leading us to investigate the need for environmental strontium in the next experiment.
  3. Average survival during the 21-d exposure of 1 g/L mixed-ions with 0, 1 and 2 mg/L strontium was 89% ± 12.7% and did not differ significantly across treatments. Growth across treatments averaged 40% ± 25.3% and was not significantly affected by treatment.
  4. All crabs in the 1 g/L mixed-ion environment (with 1 mg/L strontium) survived the 21-d exposure to temperatures of 26, 29, and 32oC. Growth in all treatments averaged 71% ± 12.1% and was not significantly affected by treatments. Due to two previous, failed experiments, 133 mg/L of sodium bicarbonate was substituted for 133 mg/L of sodium chloride to maintain pH levels above 7.5.

These results indicate that blue crabs can survive and grow in 1 g/L mixed-ion solution.

Bio: Duane Friedman was born in Philadelphia, Pennsylvania, grew up in the Naval life-style, living along most of the Eastern coastline. Following high school in West Deptford, New Jersey, he relocated to Oceanville, New Jersey, and entered the workforce. Eventually, his aspirations of working in the fisheries industry got the best of him and he became a commercial blue crab fisherman/aquaculturist. This led to an undergraduate degree, earning a B.S. in Marine Biology from the Richard Stockton College of New Jersey in Galloway, New Jersey. As part of his B.S., Duane completed an internship at the MOTE Marine Laboratory in Sarasota, Florida, culturing snook, pompano and amberjack. His journey to complete his life-long goal of becoming a Fish Biologist, Duane has had the opportunity since June of 2015, to work as a Biological Fisheries Student/Trainee at SMARC. At SMARC, he served as a caretaker in the endangered and threatened devil river minnow refugium, successfully completing production of 2800 F1 offspring. Following graduation Duane hopes to pursue a Doctorate degree and continue his career in aquaculture research for the federal government.


Thesis Defense


Harlan T. Nichols

Major Advisor:  Dr. Timothy H. Bonner           

Committee Members:  Dr. Kenneth G. Ostrand (USFWS), Dr. Joseph A. Veech


Thursday, October 22, 10:00am, Freeman Aquatic Building, Room 130

  Reductions in Edwards Aquifer spring flows are hypothesized to reduce reproductive effort of spring-associated fishes.  Purposes of this study were to test relationships among spring flow, associated habitat changes, and reproductive effort of the federally-listed Fountain Darter Etheostoma fonticola, a spring-associated fish inhabiting Comal and San Marcos rivers of central Texas. Study objectives were to quantify annual reproductive effort (i.e., ovarian stages, gonadosomatic index, and batch fecundity) across low to high flow gradients and aquatic habitats using natural and anthropogenically-altered stream reaches (N = 4) within the Comal and San Marcos rivers to represent in situ flow reductions.   Contrary to previous studies reporting year-round spawning, annual reproductive cycle of the Fountain Darter consisted of an optimal reproductive season (January through April), and tailing reproductive season (May through August), lack of spawning in September, and a leading reproductive season (October through December).  Among reproductive seasons, stages of ovarian condition, gonadosomatic indices, and batch fecundity generally were not different along a flow gradient or among habitats, though two exceptions were noted.  Gonadosomatic index and batch fecundity were greater (P < 0.05) at the higher flow environment (3.6 m3/s) during optimum reproductive season and greater (P < 0.05) at the lowest flow environment (0.01 m3/s) during the leading reproductive season.  Collectively, seasonality of reproductive effort was similar to sister taxa (Cypress Darter E. proeliare, Least Darter E. microperca), though protracted, and reproductive effort was not related consistently to flow environment observed during the study period.  However, other measures of reproductive effort (e.g., numbers of larvae hatched, survival of larvae through recruitment age) are necessary to quantify in order to assess the relationship among Fountain Darter viability and flow environments. 

Bio:  Harlan T. Nichols graduated from Texas State University in 2013 with a B.S. in Aquatic Biology. During his time as an undergraduate he published research while working as an assistant for several other projects. He is currently working toward a M.S. in Aquatic Resources.

Thesis Defense


Myranda K. Clark

Major Advisor:  Dr. Timothy H. Bonner           

Committee Members:  Dr. Kenneth G. Ostrand (USFWS), Dr. Joseph A. Veech


Wednesday, October 14, 1:00pm, Freeman Aquatic Building, Room 130


  A management strategy adopted to protect a federally-listed Fountain Darter Etheostoma fonticola during low flow conditions is the removal of a piscine carnivore Largemouth Bass Micropterus salmoides.  However, headwater spring communities with benthic Fountain Darters include another potential predator (Red Swamp Crayfish Procambarus clarkii).  Removal of a top predator, which consumes both benthic fish and crayfish, can produce a cascading effect and unintentionally increase rates of consumption on the Fountain Darter by removing top-down regulation of crayfish communities.  The purpose of this study was to test for cascading effects of benthic fish predation by quantifying number of Fountain Darters consumed by crayfish, bass, and combined crayfish and bass within vegetated and non-vegetated holding tanks.  Three water temperature trials were conducted to mimic low-flow winter temperatures (18°C), average spring-flow temperatures (22°C) and low-flow summer temperatures (27°C).  Among temperature trials, bass and crayfish and bass treatment levels consumed about equal numbers (P > 0.05) of Fountain Darters, whereas crayfish consumed the fewest number (P < 0.05) of Fountain Darters, except at 22°C.  Numbers of Fountain Darters consumed were unrelated to presences or absence of vegetation.  Collectively, study results were not consistent with cascading effects but rather with additive model of prey consumption.  As such, predator removal appears to be a viable option in reducing abnormal forms of mortality on benthic fishes during anthropogenically-induced periods of low flow, but removal efforts might create additional cascading effects.  Therefore, removal efforts should be monitored to further assess efficacy of the management strategy.

Bio:  Myranda Clark received her Bachelor’s degree at Missouri State University in Springfield, MO, majoring in Wildlife Biology.  Throughout her undergraduate career, she interned for the Heartland Inventory and Monitoring Network of the National Park Service.  Upon completion of her Bachelor’s, she moved to San Marcos, Texas to pursue her education in Aquatic Biology under the direction of Dr. Tim Bonner.  As a full-time graduate student, she continued research in fish ecology, taught various labs including Ichthyology and served as president of the Aquatic Biology Society.

Thesis Defense

The prevalence of Trypanosoma cruzi, the causal agent of Chagas Disease, in rodent populations in Texas

Adriana Aleman

Major Advisor: Dr. Dittmar Hahn

Committee Members: Dr. Michael Forstner, Dr. Ivan Castro-Arellano, and Dr. Hardin Rahe

August 6, 2015, 3:00 pm, Supple 257

Trypansoma cruzi is the parasite that causes Chagas disease, which affects over 8 million people in at least twenty-one countries in Central and South America. While Chagas disease has been recognized as a significant health threat to the 28 million people living in Central America, it has not been considered a significant threat to the people in the United States. Since rodents are one of the reservoir hosts for T. cruzi and abundant close to human housing, detections of T. cruzi in rodents provide a good approximation of the prevalence of Chagas disease and the potential threat to human health. The purpose of this study was to determine the incidence of rodents infected with T. cruzi in five geographical regions across Texas. T. cruzi was detected by real-time quantitative PCR (qPCR) in DNA extracted from heart tissue of rodents and detection assessed as a function of location, time of the season, and of rodent species. Of approximately six hundred samples analyzed, eight samples representing 6 rodent species were shown to be infected with T. cruzi, all from the most southern geographical region. The data indicate that rodent populations in selected regions of Texas are infected with T. cruzi. Further studies should be conducted to determine if other animal populations in the regions of Texas with rodent populations infected with T. cruzi may also be positive for the organism.

Bio:  Adriana was born and raised in Dallas, TX. She received her Bachelor’s degree in Animal Science with emphasis in Pre-Veterinarian in May 2013 from Texas A&M University-Commerce in Commerce, TX. She started her Master’s program in Biology at Texas State University in August 2013, and has been working as a graduate research assistant. While working on her M.S., she had the opportunity to be part of a two week “study abroad” program in Costa Rica. Her research was funded by the United States Department of Agriculture.


Summer 2015

Thesis Defense


Effects of Temperature and Nitrogenous Wastes on Survival and Growth of the Barton Springs Salamander Eurycea sosorum

Justin C. Crow

Major Advisor: Dr. Joseph R. Tomasso                                 

Committee Members: Dr. Michael R. J. Forstner, Dr. Kenneth G. Ostrand (USFWS)

Thursday, August 06, 11:00 am, Freeman Aquatic Building, Room 130

The Barton Springs Salamander (BSS), Eurycea sosorum, is a federally endangered obligate aquatic salamander found only in a few spring outflows located in a highly urbanized recreational area of Austin, Texas. The purpose of this study was to gain essential information regarding the physiological response of the BSS to thermal manipulations and three common aquatic nitrogenous toxins (ammonia, nitrite, and nitrate). All salamanders used in this study were produced at the San Marcos Aquatic Resource Center (SMARC, U.S. Fish and Wildlife Service) in San Marcos, Texas as part of a captive breeding program. To examine thermal stressors, salamanders were subjected to a nominal temperature increase of 0.5°C/day until a loss-of-righting response (LRR) was observed. Additionally, salamander growth was assessed following a 69 day trial in which young salamanders were reared at five different temperature treatments (nominal 15, 18, 21, 24 and 27°C). The cumulative ET50 of the LRR observed in the BSS was 32.6 ± 0.2°C (mean ± SD). The optimal temperature for growth of the BSS for weight and total length was estimated to be 19.0°C and 18.5°C, respectively. To investigate the effects of nitrogenous wastes on the BSS, ninety-six hour median-lethal concentration (96-hour LC50) trials were conducted for un-ionized ammonia-N (UIA-N), nitrite-N, and nitrate-N. The 96-hour LC50 of UIA-N, nitrite-N, and nitrate-N to the BSS was 2.1 ± 0.19 mg/L, 27.7 ± 0.72 mg/L, and 851.1 ± 49.21 mg/L, respectively. These results will aid in the conservation, management, and ongoing efforts to culture the BSS in captivity.

Bio: Justin Crow was born and raised in Fort Worth, Texas. Following high school he relocated to Austin, Texas and entered the workforce. Eventually, his aspirations of working in conservation biology got the best of him and he completed his undergraduate degree earning a B.S. in Marine and Freshwater Biology from The University of Texas at Austin. He then pursued his life-long goal of becoming a Fish Biologist. Justin has had the opportunity to work as a Biological Sciences Technician at the SMARC since 2013. At the SMARC he served as a caretaker in the endangered and threatened salamander refugium. Following graduation Justin hopes to remain with the U.S. Fish and Wildlife Service and continue his career in conservation. Justin is married to his loving and supportive wife Ana, and they have two amazing daughters who share their love of nature.


Thesis Defense

Determining the Seasonal Diets of Sable Antelope (Hippotragus niger) at Mason Mountain Wildlife Management Area

Amanda Hargrave

Major Advisor: Dr. Thomas R. Simpson           

Committee Members: Dr. Dittmar Hahn, Dr. Floyd Weckerly, Dr James Gallagher

July 2, 2015 at 10:00 am in Supple 153-A

Abstract: The seasonal diets of sable antelope at Mason Mountain Wildlife Management Area were investigated from June 2013 to April 2014 using microhistological technique and an emerging technique of DNA analysis of fecal material.  Forty samples were collected during summer 2013 with 20 samples collected in each of the remaining seasons. Vegetational analyses were conducted simultaneously with the fecal collection. Herbaceous plants were sampled using the Daubenmire method. Woody plants were sampled using the line-intercept method. Annually, the bulk of the diet was comprised of little bluestem (Schizachyrium scoparium) and Texas wintergrass (Stipa leucotricha). Plant use by sable antelope was compared with the availability of plants at Mason Mountain WMA to determine if sable antelope were selectively feeding. During spring, summer, and fall little bluestem (Schizachyrium scoparium) was selected. During the summer, switchgrass (Panicum virgatum) was also selected. Sable antelope selected Texas wintergrass (Stipa leucotricha) during the winter.  DNA analysis targeted a portion of the chloroplast trnL (UAA) intron and 13 samples were successfully amplified and sent to the University of Texas at Austin’s Genomic and Sequencing Analysis Facility for next-generation sequencing. The vast majority of plants consumed by sable antelope were grasses. While sable antelope may not compete for food resources with browsers such as white-tailed deer and greater kudu, careful consideration should be made when stocking with other grazers such as cattle, waterbuck, gemsbok, and scimitar-horned oryx.

Bio: Amanda Hargrave was raised in a small town in East Texas called Mabank where she first developed an interest in the natural world. She began her undergraduate career at Trinity Valley Community College and obtained an associate’s degree in liberal arts. She received a Bachelor of Science in Wildlife Biology in 2012 from Texas State University in San Marcos, Texas. While completing her undergraduate requirements she served as both vice president and president of the student chapter of The Wildlife Society and obtained an internship with Texas Parks and Wildlife Department at Government Canyon State Natural Area. In 2013, she entered the graduate program in Wildlife Ecology at Texas State University. While enrolled in the program she completed a second internship with Texas Parks and Wildlife Department at Mason Mountain Wildlife Management Area. As a graduate student she completed the GIS certification requirements through the geography department and worked as an instructional assistant for Modern Biology II, Techniques in Wildlife Management, and Vertebrate Natural History. Amanda’s goal is to help manage and conserve the natural resources and wildlife in Texas, while also gaining experience in the field and becoming more knowledgeable on ecological relationships and resource management.


Dissertation Defense


Praveen Kumar Kathare

Major Advisor: Dr. Nihal Dharmasiri

Committee Members: Dr. Dana Garcia, Dr. Hong Gu Kang, Dr. Sunethra Dharmasiri,

                                 Dr. Rachell Booth, Dr. Enamul Huq       

Wednesday, July 1, 2015, 02:00 PM Supple 257

The plant hormone auxin regulates many key aspects of plant growth and development as well as plant response to both biotic and abiotic stresses. This is mainly achieved through controlled gene expression of group of three early auxin responsive gene families. SAUR (Small Auxin Up RNA) family of genes are one of three early auxin responsive genes, whose expression is induced within minutes of auxin application. In model plant Arabidopsis, SAUR family consists of more than 72 genes. However, except for few genes, functions of most of these SAUR genes are not known. With the aim of functional characterization of some of Arabidopsis SAURs, we selected four different SAUR genes belonging to clade III of the SAUR family. Results from this work indicate that all the four SAUR proteins physically interact and form complex with calmodulin proteins. These four genes are involved in the regulation of cell and organ elongation, and therefore, overexpression of any of these genes results in pleotropic growth related defects. SAUR overexpression transgenic seedlings are defective in polar auxin transport and are significantly insensitive to plant hormone ethylene. Moreover, SAUR overexpression and loss-of-function mutants show altered responses to salinity and drought stress responses. Taken together these data suggest that all four SAUR genes are important modulators of plant growth and development, and also regulate plant responses to environmental stresses.

BIO: Praveen Kumar received his BS majoring in Biotechnology from Gulbarga University- Gulbarga, India and MS in Biotechnology from Bangalore University- Bangalore, India. He entered aquatic resources Ph.D. program in spring 2010. As an instructional assistant he has taught laboratory courses in plant physiology and developmental biology. He is also working as a research assistant in the Department of Biology.


Thesis Defense

Characterization of AFB5 in Arabidopsis Auxin Signaling

Lauren Minter

Major Advisor: Dr. Nihal Dharmasiri                      

Committee Members: Dr. Sunethra Dharmasiri and Dr. Dhiraj Vattem (Department of Nutrition and Foods)

Monday, June 29, 2:00 PM, Norris Room  

 Auxin regulates nearly every aspect of plant growth and development by controlling both genomic as well as non-genomic responses. Genomic responses are regulated through the degradation of a group of transcriptional repressors called Aux/IAA proteins. These repressors are degraded through the ubiquitin-proteasome pathway involving SCFTIR1/AFBs in which TIR1/AFBs function as auxin co-receptors. TIR1 gene family in Arabidopsis consists of 6 genes, of which AFB4 and AFB5 are distantly related to TIR1. We isolated two mutant alleles of Arabidopsis AFB5 (pic3 and pic59) through a genetic screen using picloram, a synthetic auxin commonly used as an herbicide.

            Both mutant alleles exhibit differential primary root growth resistance to different auxinic chemicals. AFB5 expresses highly in tissues with actively dividing cells, such as the primary and lateral root tip, lateral root primordia, and hypocotyl, suggesting that AFB5 may function in cell division and/or expansion. Altered lateral root densities have been observed in pic3 and pic59 and AFB5::AFB5-GUS expresses highly in lateral root primordia, indicating that AFB5 may regulate lateral root development. Results so far indicate that AFB5 may have a limited role in Aux/IAA degradation, suggesting that it functions partially or completely differently from TIR1. Additionally, recent published data suggests that ROP GTPases regulate both auxin and ABA signaling. Two members of this family, ROP2 and ROP6 express highly in actively dividing tissues and mutants show defects in lateral root development. We hypothesized that the functions of AFB5 may be regulated through ROP GTPases and found that AFB5 expression is significantly higher in the rop2 and rop6 background. Using phenotypic analysis of rop2 or rop6 and afb5 double mutants, we sought to identify the role of AFB5 in plant growth and development.

Bio:  Bio:  Lauren was born and raised in Austin, Texas. In 2013, she earned a B.S. in Biology with a minor in Women's Studies from Texas State University-San Marcos, during which she conducted undergraduate research in the Dharmasiri lab. Upon completion of her bachelors, she join the lab as a full-time graduate student, where she continued research on auxin signaling, taught a variety of labs as an Instructional Assistant, and served in the Student Government as the Graduate Representative for the College of Science and Engineering.


Thesis Defense


The effects of net confinement and rapid salinity change on red drum (Sciaenops ocellatus) fed supplemented diets

 Shawntel M. Lopez

 Major Advisor: Dr. Joseph Tomasso              

Committee Members:  Dr. Dittmar Hahn, Dr. Michael Forstner, and Dr. Hardin Rahe

 Friday June 26, 2015, 9:00 AM FAB 130

Due to increasing temperatures and changing precipitation patterns, hatchery raised juvenile red drum are sometimes faced with abrupt environmental changes when stocked into coastal bays. For this study, red drum fingerlings were fed either a reference or supplemented diet (2% salt, 2% salt and a prebiotic, 3% salt, 5% salt, or 7% salt) to determine if diet supplementation fostered better tolerance to net confinement and rapid salinity changes. Fish were fed diets for four to five weeks and then confined in a net for one hour, during which salinity was increased to either 40‰ or 55‰. Seventy-two hours after confinement, 100% survival was seen in those placed in the 40‰ and 0-47% survival was seen in treatment groups raised to 55‰. Plasma osmolality levels, plasma glucose concentration, plasma lactate concentrations, liver glycogen levels and hematocrits showed no significant variation across diet treatments or when comparing pre- and post-confinement values. Results of this study suggest that red drum fed a salt supplemented diet may be able to better tolerate rapid salinity increase, but further research is needed. However, if we compare performance of fish fed the reference diets in both experiments, it is clear that transfer of red drum to 40‰ may be feasible, but transfer to 55‰ risks losses of some or all of the fish.

Bio:  Shawntel M. Lopez was born and raised in Pasadena, Texas. She graduated from Texas State University in August of 2013 with her Bachelors degree in Biology, and immediately began work on her Masters degree in Biology at Texas State University. Upon graduation, she will return to her hometown of Pasadena, TX to mold the minds of future scientist as a high school Biology teacher.


Thesis Defense




Derek M. Wallace

Major Advisor:  Dr. Michael R. J. Forstner           

Committee Members: Dr. Jennifer Jensen, Dr. Joseph A. Veech

Thursday, June 25, 2015, 1:00 pm Supple Science Building, Norris Room

The loss of biodiversity worldwide is an issue of great concern and in the last quarter century amphibians have been at the forefront of this issue. Of particular note for South-Central Texans is the regional species Bufo houstonensis (Houston Toad). B. houstonensis is a Texas endemic amphibian first described as a species in 1953 and was the first amphibian listed on the U.S. Endangered Species Act in 1970. Historically the species has been found in the following counties: Austin, Bastrop, Burleson, Colorado, Fort Bend, Harris, Lavaca, Lee, Leon, Liberty, Milam, and Robertson, but is reported to be extirpated from Harris, Burleson, Fort Bend and Liberty counties. To date, Bastrop County has maintained the largest population since the 1970’s. The causes behind B. houstonensis’ decline across the range are largely attributed to habitat destruction and degradation. In addition to habitat destruction, two severe droughts have occurred across the range of B. houstonensis, the most recent resulted in a severe wildfire which drastically reduced critical habitat within Bastrop County. In 2001, the United States Fish and Wildlife Service established Focus Areas in order to direct conservation within smaller areas across the species range. Given the endangered status of B. houstonensis it is necessary to better understand these Focus Areas regarding the habitat of B. houstonensis on a temporal basis and use any information derived to assist in future conservation efforts.

Bio: Derek Michael Wallace was born in Longview, Texas and relocated to Central Texas in 2001. He enrolled in Texas State University – San Marcos in 2004 and received a B.S. in Biology, with a minor in English, in 2008. After two years working for the Texas Department of State Health Services he enrolled in the Wildlife Ecology Masters program at Texas State University – San Marcos in 2011. Between 2011 and present he also worked as a biological consultant performing field work for the protection and conservation of the Houston Toad.


Thesis Defense


Sarah Weber

Major Advisor: Dr. Randy Simpson and Dr. John Baccus

Committee Members:  Dr. Michael Clay Green

Thursday, June 25, 2015, 11:00 AM Room 153

Because of perceived declines in golden eagle (Aquila chrysaetos) populations in the western United States, United States Fish and Wildlife Service (USFWS) are closely monitoring population trends throughout their range.  An inventory of golden eagles in 2 ecosystems in Nevada (northern Mojave Desert and southern Great Basin) was conducted from 2011-2014 with the objectives to: (1) locate nest sites and territories across several mountain ranges (Kawich Range, Belted Range, Stonewall Mountain, Cactus Range, Black Mountain, Quartz Mountain, Tolicha Peak, Sheep Mountain, Pintwater Range, Desert Range, Pahranagat Range, Spotted Range, Buried Hills, Half Pint Range),  (2) estimate breeding population, and (3) map suitable nesting habitat based on nest site parameters. Cliff and canyon habitats of the southern Great Basin and northern Mojave Desert were surveyed by helicopter from 2011-2014 for active and inactive nests and to measure nest site parameters. Nest site parameters used for analysis were: general location, mountain range, cliff height, viewshed, soils, geology, elevation, aspect, slope, habitat, use, productivity, distance to nearest road and distance to water. Using these parameters, a suitability index was created using the program MaxEnt to map potential nesting habitat throughout they study site boundaries. A total of 96 nest sites (old/abandoned and newly decorated) were analyzed. During the four years of inventory 27 active nests produced 36 fledglings. Two nests were occupied for three years and three nests had double year occupancy. Results of this project will aid in establishing a monitoring program to provide guidance for avoiding and minimizing disturbances and other kinds of future “take” for federal agencies in consultation with USFWS.

Bio:  Sarah A. Weber was born in Indianapolis, IN and moved to San Antonio, Texas in 1998. She graduated from Texas A&M University in 2006 with a B.S. in Wildlife and Fisheries Science and a concentration in Conservation Biology and Biodiversity. Sarah has continual education in Geographic Information Systems (GIS) from Penn State University and has a current application pending for Certified Wildlife Biologist through The Wildlife Society. Sarah is president and co-owner of a biological and spatial surveying company called Bio-Spatial Services, Inc. Sarah has been in the consulting field for eight years and is looking forward to continuing to provide high quality expertise in the field of Natural Resources. Sarah is an avid field biologist and enjoys helping landowners (public and private) manage their wildlife and biological resources with sound science and wise use.

Sarah has a 4 year old daughter, Olive and lives in the Texas Hill Country. 


Thesis Defense

The Physiological Effect of Hypersalinity and Temperature

on Juvenile Red drum

Erica M. Molina

Major Advisor:  Dr. Joseph Tomasso       

Committee Members:  Dr. Dittmar Hahn, Dr. Michael Forstner and Dr. Hardin Rahe

Thursday June 25, 2015, 8:00 AM FAB 130

Recreational and commercial fishing have decreased the population of many fish species. As a consequence, fish hatcheries in many costal states produce fingerlings, for stocking, in effort to increase overfished populations. The purpose of this study was to determine the physiological response of juvenile red drum to warm, hypersaline conditions in order to determine whether fish are able to acclimate to life in the wild during drought conditions (ie. very low instream flows to the bays). Red drum, Sciaenops ocellatus, fingerlings were cultured in recirculating systems for 4-5 weeks at different temperature/salinity regimen, i.e. at a temperature of 30°C and a salinity of 35 ‰ (reference conditions), and a temperature of 34°C and either 45 ‰, or 55 ‰ salinity (treatment conditions). Comparison of physiological stress indicators such as hematocrits, plasma osmolality concentrations, plasma lactate concentrations, plasma glucose concentrations and liver glycogen levels in fish held under reference conditions or increased temperature and salinity regimen did not result in statistically significant differences between treatments. Indicating, that as long as food is not limiting and water quality is acceptable, juvenile red drum can tolerate warm, hypersaline conditions with no apparent detrimental effects, if gradually acclimated to environmental conditions prior to exposure to these conditions.

Bio:  Erica was born and raised in San Antonio, Texas. She received an Associates degree in Veterinary technology from Palo Alto College and has worked as an LVT at the Emergency Pet Center while in school. She also received her Bachelors in Animals Science with a minor in Biochemistry and then immediately went into her Maters program in Biology at Texas State University. After graduation she will be moving to Auburn, Alabama to pursue her PhD in Biology under the supervision of Dr. Mendonca. 


Thesis Defense

Effect of compost tea on plant growth performance and the fate of microbial communities in soil

Name Elise Claire Valdes

Major Advisor: Dr. Dittmar Hahn

Committee Members: Dr. Michael Forstner, Dr. Robert McLean, and Dr. Hardin Rahe

June 24, 2015, 10.00 AM, Supple 257

Compost tea is a popular amendment used to improve soil quality and to control soil-borne diseases in plants. With proper brewing, compost tea contains many of the beneficial microbes and nutrients of compost, but is more easily applied to plants. The purpose of this study was to (i) analyze the fate of microbial communities in spent mushroom substrate compost tea applied to soil microcosms planted with corn, and (ii) determine if growth of corn is influenced by specific constituents from compost tea, including microbes only, nutrients only, or a combination of both (i.e. the complete compost tea). Two trials were performed, one with anaerobic soil conditions and a second with aerobic soil conditions. Bacteria and Eukarya were quantified over the 30 days with sampling events on days 0, 1, 2, 5, 10, 20, and 30, as were plant growth performance characteristics like root and sprout length or their biomass. Results demonstrated a significant drop (70-90%) in abundance of microbes after application of compost tea, without recovery during the 30-day incubation period. Plant growth performance characteristics were not statistically significantly different for corn on soil receiving compost tea or separated components (i.e. microbes or nutrients) only, or a water control. While these results cannot support assumptions on beneficial effects of compost tea on plant growth performance and microbial communities in soil after application, further scientific research should consider long-term studies with different plant species and soils to further investigate potential beneficial effects of compost tea.

Bio:  Elise Claire Valdes is originally from Sugar Land, Texas. She received her B.A. in Agriculture- Animal Science from Texas State University. She initially became interested in sustainable agriculture after a trip to the Galapagos Islands. Soon after, she received the opportunity to get her Master’s degree in Biology at Texas State University under a USDA grant and with a sponsorship from the Kitchen Pride Mushroom Farm, Inc. The grant allowed her and five other students to go on a study abroad to Costa Rica last May, where she gained further insight into the dynamics of sustainable living.


Thesis Defense

Population Genetics of the Big Bend Slider (Trachemys gaigeae gaigeae) and the Red Eared Slider (Trachemys scripta elegans) in the Contact zone in the Lower Rio Grande drainage of Texas

Name: Lauren Schumacher

Major Advisor:  Dr. Michael R.J. Forstner (Chair)   

Committee Members: Dr. M. Clay Green, Dr. Thomas R. Simpson

Monday, June 22, 2:30 PM, Supple Science Building, Norris Room

The red-eared slider (Trachemys scripta elegans) is well-known for its popularity in the pet trade. It is also known for its near cosmopolitan distribution, which is partly due to the release of these pet turtles. When introduced to a new area, non-native T. s. elegans can hybridize with other native Trachemys species. An example of this occurs between T. s. elegans and the Big Bend slider (T. gaigeae gaigeae) in western Texas. Recent research and trapping efforts have primarily focused on Big Bend National Park. Mitochondrial haplotypes unique to T. g. gaigeae have been observed in T. s. elegans inhabiting Rio Grande tributaries downstream of the park, which could indicate historical hybridization. This study sought to address these concerns by utilizing specifically targeted additional sampling within these areas. I used twenty polymorphic microsatellite loci and model-based clustering methods to detect hybrids. Out of the 120 turtles sampled, 7.5% were identified as hybrids using the program Structure v2.3.4, and 23.3% were identified as hybrids using NewHybrids v1.1. My results supported the findings of past research as hybridization was found between T. g. gaigeae and T. s. elegans. They also supported the idea that morphology cannot identify hybrids. Some of the backcrossed individuals were located in areas outside of the range of T. g. gaigeae. This may represent an ancestral polymorphism caused by previous gene flow between individuals in the Rio Grande, Pecos River, and Devils River.

Bio: Lauren grew up in a small town in southern Illinois where she was constantly bombarding her classmates with fun facts about one animal or another. She eventually moved to Florida to earn her B.S. in Marine Biology from Florida Institute of Technology. After graduation, she started working at the Dauphin Island Sea Lab where she assisted with a number of projects that involved the restoration and subsequent monitoring of coastal marine habitats. This was followed by three months of fieldwork in the Mojave Desert assisting with a desert tortoise disease ecology project out of the University of Nevada, Reno. She joined the Population and Conservation Biology Masters Program at Texas State in the fall of 2012. While at Texas State, Lauren has taught Genetics labs and worked as a Houston toad monitor.


Thesis Defense

Landscape scale habitat associations of Sprague’s Pipit (Anthus spragueii)

overwintering in the southern United States

John A. Muller

Major Advisor:  Dr. Joe Veech           

Committee Members:  Dr. Clay Green, Dr. Rich Kostecke (Nature Conservancy)

Monday, June 22, 10:00 AM in Norris Conference Room

Sprague's Pipit is a North American endemic migratory grassland songbird that has experienced a substantial population decline over the last half-century. There has been very limited research done on Sprague’s Pipit especially on their wintering grounds. There is no complete account of their historic wintering range and there is also limited knowledge about the status of their current wintering range in the United States and Mexico. On the breeding range, Sprague’s Pipits seem very selective in their habitat use, although there are reports that there may be a broader use of habitats on the wintering grounds. My objective was to determine the habitat types that Sprague’s Pipit associates with at the landscape scale. I used land cover data from the National Land Cover Database GIS layers, CropScape GIS layer, and pipit point locations retrieved from eBird. I examined landscape-scale (1, 2 and 5 km) habitat associations of Sprague’s Pipits over wintering in areas of Arizona, New Mexico, Texas, and Louisiana. I then compared these habitat associations to those of random locations and to locations of the closely related American Pipit. I found that Sprague’s Pipit locations had minimal canopy cover, lower percent cover of woody vegetation and certain agriculture land cover types in comparison to random locations. I also found that although Sprague’s Pipit is known to be negatively affected by non-native and anthropogenic grasslands at fine spatial scales, these grassland types may be suitable for the species at the landscape scale. Sprague’s Pipit also appeared to be much less of a habitat generalist than the more common American Pipit.  The results of my study could potentially be used in landscape-level planning for the conservation of the species on its wintering grounds.

Bio:  John was born and raised in Austin, TX. He received a B.S. in Wildlife Biology from Texas State University in 2012. After receiving his bachelor’s degree he worked as a biotech and wildlife monitoring intern for the USFWS for 18 months at both Tishomingo NWR, Oklahoma and Buenos Aires NWR along the Arizona/Mexico border. He started the M.S. program in Wildlife Ecology in January of 2014, and has been working as a graduate research assistant.


Dissertation Defense

Efficacy and Efficiency of Head-starting and Captive Propagation of an Endangered Amphibian: Implications for Continued Population and Habitat Management Following Catastrophic Wildfire

Melissa Jones

Major Advisor: Dr. Michael Forstner
Committee Members:  Dr. Dittmar Hahn, Dr. Floyd Weckerly, Dr. Audrey McKinney and Dr. Todd Swannack

Friday, June 19, 2015, 11:00 AM Norris Room

The Lost Pines ecoregion of Texas is a loblolly pine (Pinus taeda) and oak (Quercus stellata) dominated woodland forest with remaining fragments in Austin, Bastrop, Colorado and Fayette Counties. Bastrop County Texas continues to support the largest known and best studied population of Houston toads (Bufo [Anaxyrus] houstonensis). The Houston toad was first described in Houston, Texas in 1953, and was the first animal from Texas and first amphibian federally listed as an endangered species.  To date, nearly all recovery efforts have centered on the “robust” population remnant in Bastrop County. Houston toad populations have remained in a continual decline consequent of multiple stressors, including habitat fragmentation, urban growth of the city of Bastrop, red imported fire ants, fertilizers and chemical run off, agricultural practices, drought, and most recently, catastrophic wildfire. The aftermath of the Bastrop County Complex fire of 2011 has left the county with the need for immediate, active and continual restoration of plant communities on public and private land. This recent fire event now presents us with the rare opportunity to explicitly test habitat suitability and species survivorship pre and post catastrophic wildfire on native amphibian populations. I seek to provide data that are relevant to continued population conservation programs and the ongoing habitat remediation and restoration efforts in Bastrop County. I have investigated 1) the efficacy and effectiveness of head-starting and captive propagated releases of Houston toads; 2) assessed habitat suitability and the effects of catastrophic wildfire on Houston toad populations, and 3) assessed familiarity and community support of recovery efforts for the Houston toad among Bastrop residents. My results will guide future management strategies and contribute to conservation recovery efforts for the remaining Houston toads in this altered landscape.

Bio:  Melissa Jones was born in San Antonio, TX on March 29th 1980 to Curtis and Carolyn Jones.  In 2002, she received her Bachelors of Science degree in Zoology from Southwest Texas State University. In 2004, she returned to Texas State University and received her Masters of Science degree in Wildlife Ecology in 2006. In 2010, she entered the Aquatic Resources doctoral program at Texas State University to focus on habitat and population management of the endangered Houston toad.


Thesis Defense


Andrew R. MacLaren

Major Advisor:  Dr. Michael R. J. Forstner           

Committee Members: Dr. Shawn F. McCracken, Dr. Floyd W. Weckerly

Friday. June 19, 2015, 8:00 AM Supple Science Building, Norris Room

 Abstract:  Amphibian populations are experiencing rapid rates of decline, the causes of which are sometimes controversial. The vocalization of the male anuran is used as an indication of a potential breeding event. Researchers have been relying on these vocalizations to monitor the health, reproductive status, and diversity of anuran populations for centuries. As technology advances so does our ability to innovate and improve the way anuran populations are monitored. One such innovation comes in the form of portable commercially available audio recording devices (ARD). These tools enable researchers to capture the sounds produced by populations of any vocalizing animal species and analyze them using machine-learning techniques of pattern recognition. The application of these techniques is understudied and not well documented for anurans. I conducted rigorous testing of these techniques to improve methods of monitoring populations of the endangered Houston Toad (Bufo houstonensis). The desired result of these tests would be a reliable and robust tool for recognizing the call of the Houston Toad. This would allow researchers to search vast quantities of digital audio files for the unique sound of this animal. I also compared the efficacy of this machine-learning technique to a highly trained professional listening for the call. Researchers often doubt the reliability of automated techniques, thus my recognition tool must be able to perform capably. Additionally, I employed these automated machine-learning techniques to document the presence or absence of the Houston Toad in two counties of Texas, and then coupled those data with highly resolute details of the environmental conditions to examine call phenology of the Houston Toad and graphically visualize this behavior across a complete chorusing season.

Bio: Andrew MacLaren relocated to Houston, Texas from Bay City, Michigan in 2000. Received a B.S. Biology, minor in Philosophy, in December of 2013 from Texas State University - San Marcos. He joined the Master of Biology program here at Texas State beginning June 2014. He also worked as a biological consultant monitoring populations of Houston Toads in the interim of his enrollment as a student.


Thesis Defense

Using a Habitat Suitability Model and Molecular Analyses to Aid in the Conservation Management of the Texas Tortoise, Gopherus berlandieri

Anjana Parandhaman

Major Advisor:  Dr. Michael R. J. Forstner           

Committee Members: Dr. Shawn F. McCracken, Dr. Thomas R. Simpson, Dr. M. Clay Green

Thursday, June 18, 2015, 2:00 PM Supple 257-A

The Texas tortoise, Gopherus berlandieri, is a threatened species in the state of Texas and strict conservation action is required to ensure that continuing population decline does not occur. The historical range of the Texas tortoise includes a much larger area than recent observations support, especially in the eastern range. Assessing the habitat suitability of the eastern historical range of the species and determining whether this region still supports the species will aid in its conservation. For the first chapter of my thesis, I conducted road surveys, from March to October of 2014, in these understudied regions. GPS coordinates of tortoises from these surveys, along with coordinates obtained from online databases were used with environmental predictors to model habitat suitability for the species using ArcGIS and Maxent. I found that there are some patches of habitat in the eastern range that could potentially support the species. In addition, some areas of suitability exist outside the species range. For the second chapter of my thesis, a population genetics study was carried out using tortoise samples, found outside its current and historic range, to determine genetic diversity and population structure using microsatellite loci. I found that selected tortoises likely belong to the same population, although some loci have a relatively high amount of genetic diversity. Both of my chapters attempt to explain the poorly understood factors of habitat suitability and aid in genetic diversity research for the Texas tortoise. This in turn will allow for better management and conservation of the species throughout its range.

Bio: Anjana was born in a land far, far away (also known as Chennai, India) and obtained her Bachelor’s degree in Zoology from Stella Maris College, Chennai, in 2011. She spent a year working on coastal issues, crocodiles and Olive Ridley Sea turtles, and volunteered for various other organizations. Anjana then moved to Texas, joined the Masters program in Wildlife Ecology at Texas State University in January of 2013, and has been trying to do awesome science ever since. 


Spring 2015

Thesis Defense


Jacob N. Bilbo

Major Advisor: Dr. Thomas B. Hardy             

Committee Members: Dr. Paula S. Williamson & Dr. Weston H. Nowlin  

Friday, April 24, 2015, 1:30 PM FAB 130

Abstract:  Hydrilla (Hydrilla verticillata) is an invasive species that is problematic globally and also in the San Marcos River where it competes with native species. Hydrilla has been described as the “perfect aquatic weed” because it is able to propagate under a wide range of environmental conditions including low nutrient and variable light conditions (Langeland 1996). Treatment methods for control of non-native aquatic plants can be restricted due to the co-occurrence of native endangered species, requiring an integrated approach of several methods for restoration, including removal by hand, and manipulating environmental factors to encourage growth of native species. I conducted a competition study to determine if native species can out-compete non-native species under a set of environmental conditions. The experiment was conducted within Spring Lake at the headwaters of the San Marcos River, Hays Co. Texas between 03/28/2014 and 05/21/2014. I used a three-factor replacement design: (water velocity, substrate type, and competitive pressure) to assess competitive interaction between a native and non-native aquatic macrophyte. Illinois pondweed (Potamogeton illinoensis) and hydrilla were potted in monoculture (intraspecific competition) and mixtures (interspecific competition) using sand or silt sediment, and high or low velocity for a period of seven weeks. Above- and belowground dry biomass, total stem length, and number of stems were measured. Across all treatments, pondweed demonstrated significantly (P<0.05) higher growth rates than hydrilla. Substrate type and monocultures were not statistically significant factors in plant growth, however growth indices indicated that total dry biomass of both plants was slightly higher in sand substrate and high velocity. I also found intraspecific competition was greater than interspecific competition for both species, and that both species produced more biomass when in monoculture and at lower ratios in mixtures. Therefore, data from this study suggests optimal growing conditions for Illinois pondweed to out-compete hydrilla are in sand substrate and high velocity conditions. Continued research is required to further understand the competitive interactions of native and non-native macrophyte species in the San Marcos River.

Bio:  Jacob Bilbo is originally from El Paso, TX where he earned his B.A in Interdisciplinary Studies at the University of Texas at El Paso. He became interested in aquatic biology after researching arctic zooplankton community dynamics for his senior thesis. While pursuing his M.S. in Aquatic Resources at Texas State University, he has worked as a consultant for the Southeastern Aquatic Resources Partnership. He then worked as a graduate research assistant at the Meadows Center for Water and the Environment conducting habitat restoration in the San Marcos River.


Thesis Defense

Small mammal communities and urban land cover associations in

San Marcos, Hays County, TX

Lauren Cody

Major Advisor: Dr. Thomas R. Simpson            

Committee Members: Dr. M. Clay Green and Dr. Ivan Castro-Arellano

April 17, 2015 1:00 PM SUPP 153-A

The importance of understanding small mammal diversity in urban areas is multifaceted. Small mammals affect predator population dynamics, habitat structure, and the spread of zoonotic diseases. Small mammal populations can help evaluate habitat fragmentation and quality and can potentially delineate habitat management strategies. My objectives were to determine the composition and diversity of small mammal communities within the city of San Marcos, and to evaluate relationships between composition and diversity by meteorological seasons and land cover type. I surveyed 20 sites within urban San Marcos between August 2013 and May 2014 for a total of 11,590 trap nights over 4 seasons. A total of 280 small mammals among 12 species were captured; the hispid cotton rat (Sigmodon hispidus) had the highest relative abundance overall (46.1%), in all seasons, and in all land cover types except urban developed, where the house mouse (Mus musculus) was most abundant. The northern pygmy mouse (Baiomys taylori) was also significantly more abundant than other captured species. Grassland sites showed the highest trap success (7.7%). The highest diversity index (1.39) and species richness (n = 5) were found in Speck Parking Lot, an urban developed site. Bicentennial Park, classified as forest/woodland, yielded no captures over the entire survey period. The Lower Purgatory Greenspace area, a grassland site, had the highest relative abundance (n = 87) and trap success (15.9%). While I did not find a significant difference in species diversity based on land cover type or season, more surveys should be conducted to gain a clearer picture of the small mammal communities of this area. Many sites did not yield any captures during some or all seasons, potentially deflating species diversity indices. I also saw fewer captures in the spring season, most likely due to the extreme cold winter season experienced by the San Marcos area. Two of the forest/woodland sites had large stands of privet trees (Ligustrum spp.), which likely account for lower relative abundance in those areas. Now that areas with high abundance and diversity of small mammals have been identified in San Marcos, these sites can provide opportunities for future surveys and projects, and can be used to assess and monitor the habitat quality of this urban area.

Bio:  Lauren Cody was born in Fort Sill, OK, but quickly moved to Texas. She grew up in San Antonio and received her B.A. in Biology from the University of Texas at Austin in 2007. After working in environmental testing for a pharmaceutical company in North Austin, she decided to pursue higher education. While working towards her M.S. in Wildlife Ecology here at Texas State University, she has volunteered with Austin Water Quality and Plateau Land and Wildlife Management, and has been an IA for Functional Biology labs.


Thesis Defense


Lorissa Di Giacomo

Major Advisor: Dr. M. Clay Green          

Committee Members: Dr. Ivan Castro-Arellano & Dr. Thomas R. Simpson  

Monday, April 13, 2015, 12:00 PM Supple 153-A

Habitat parameters that affect survival and reproduction can be enhanced or degraded from human activities including disturbance and development. While the development of human-made structures can obviously degrade (e.g. loss of habitat) a species’ ability to survive and reproduce, human structures can also promote population growth through a species use of these structures for basic life history requirements, such as nesting and roosting. My study examined the overlap (spatially and temporally) of Cliff Swallows and Cave Swallows during the nesting season as well as the seasonal use of 5 bridges in Central Texas by both species. Specifically, I examined spatial isolation between swallow species and investigated the influence of temperature and ambient light properties on nest site selection. For both years of this study, Cliff and Cave Swallows were present during our surveys; while the numbers were variable between years and among bridges, in general Cliff Swallows were the dominant species present. In contrast, Cave Swallows were only recorded at two of the five sites: B2-Plum Creek, and B5- Blanco State Park during both years. I found no significant interaction between bridges and probe (F = 0.901, P = 0.493) for mean temperature (°C) but the three bridges (B2, B3, B5) did significantly differed in mean temperature with B2 significantly warmer than B3 and B5 (F = 15.104, P <0.001). For mean light (Lux), I found a significant interaction between bridge and probe (F = 63.75, P <0.001) with all bridges receiving less light within the interior spans then the outer spans and the bridges differing significantly in overall ambient light; in order of decreasing light: B2, B3 and B5. Cave Swallows were found only within the interior spans of bridges (i.e. darker areas) and at the two bridges that received the less light. However, Cave Swallows did not appear to be influenced by temperature as Cave Swallows occupied the hottest (B2) and coolest (B5) bridges. Based on my results, it appears Cave Swallows are selecting bridge site that are relatively dark but not influenced as much by temperature at the nest site. Future studies are warranted to continue investigating the nest site selection of Cave Swallows as they continue to expand their range into the south western United States.  

Bio:  Lorissa Di Giacomo earned a B.A. in Biology from Texas Lutheran University in 2012. While in college, she worked at the San Antonio Zoo as a Playleader. As a Population and Conservation Biology Master’s student at Texas State University, she was funded to do her research from Texas Department of Transportation. Upon graduation, Lorissa hopes to work for TPWD but until that time she will remain at the San Antonio Zoo, where she has been a part of for the past 11 years.


Dissertation Proposal Defense


Investigating Population Structure and Evolutionary History of Three Focal Taxa

in the Edwards – Trinity Aquifer System Using Integrative Systematic Methods

Emrah Ozel

Major Advisor: Dr. Michael R. J. Forstner             

Committee Members: Dr. David R. Butler, Dr. Benjamin F. Schwartz, Dr. Chris Nice, Dr. Marshal Hedin

Monday, April 13, 2015, 9:00 AM, Supple 257A

Caves are fascinating environments that harbor many obligate and facultative organisms. In general, these species share a set of troglomorphic characters at various degrees depending on their life cycles. Darkness, relative climatic stability and significant humidity lead the convergent evolution of subterranean lineages. Three focal taxa (Asellidae, Stenasellidae, Cirolanidae; Order: Isopoda / Ceuthophilus; Order: Orthoptera / Cambala, Speodesmus; Class: Diplopoda) in the Edwards – Trinity Aquifer system are selected to investigate the influence of these physical and climatic habitat features on subterranean evolution and population structure. Studies showed that morphological analysis can easily be deceived by the convergent nature of subterranean evolution. On the other hand, molecular techniques provide deeper insights on phylogeny and population structure; however, it is still a controversial idea to use molecular methods solely for defining species boundaries. Integrative systematics is a recent trend in biology aims to utilize various data sources for species delimitation process. In this study, I will seek to use high resolution three-dimensional morphological data, molecular genetic data including nuclear, mitochondrial and anonymous DNA markers and basic climatic data to infer species boundaries. In addition to this, taxon sampling will allow assessing colonization histories, habitat connectivity and inter/intra-cave variations. Also, using these analytical methods, some other parameters such as strength of convergent evolution and the effect of UV radiation can be estimated. Lastly, my research will be one of the few studies that follows an integrative approach to evaluate subterranean evolution in the Edwards – Trinity aquifer system of Central Texas.

Bio: Emrah Ozel earned a BSc. degree in Biology from Hacettepe University, Ankara, Turkey. In 2010, he received a MSc. in Zoology from Hacettepe University, Turkey. He entered the Ph.D. program in the Department of Biology at Texas State University in Fall 2011. As a Ph.D. student, he has been employed as an instructional assistant for Genetics lab.


Thesis Defense

RIO GRANDE BEAVER (Castor canadensis mexicanus)  SURVEY IN


Howland J. Reich IV

Major Advisor: Dr. Thomas R. Simpson

Committee Members: Dr. Floyd W. Weckerly, Texas State University & Dr. M. Clay Green, Texas State University

Thursday, April 9, 2105, 2:00 PM, LBJ 3-3.1

 The Rio Grande River and its tributaries are home to the southwestern subspecies of North American beaver, Castor canadensis mexicanus. National Park Service biologists and biologists of protected areas in Mexico are concerned with the status of beaver populatons in this area. The last survey for the Rio Grande beaver, sometimes known as the Mexican beaver, in Big Bend National Park was conducted in 1981 by P. Strong and J. Bissonette. My objectives were to document centers of beaver activity and estimate the beaver population in Big Bend National Park. I surveyed 130 km of Rio Grande River with kayaks and canoes from the mouth of Terlingua Creek to the mouth of Boquillas Canyon during several trips from February 2013 to May 2014. I recorded water depth, type of vegetation, sign of active beaver colonies (dens, beaver tracks, scat, and cuttings), and ranked the amount of beaver activity within each colony as high, medium or low.  From these data, I created a map in ArcGIS showing bathymetry of the river, vegetation profiles, and sites of active beaver sign. I delineated a total of 98 active beaver colonies in the study area. Analysis of water depth with respect to den locations indicated that colonies were located in the deeper pools along the Rio Grande.  I conducted camera surveys on 11 colonies to estimate the number of beaver in each colony.  With camera survey data and activity ranking of each colony, I estimated a population of 185 beaver occupying the 98 colonies. This represents a 38% increase in the beaver population along the Rio Grande since the 1981 survey.

Bio:  Howland J. Reich IV (Joey) earned a B.S. in Wildlife Biology from Texas State University- San Marcos in 2013.  While in college, he worked as a wildlife biologist for a private landowner in the Texas hillcountry.  As a Wildlife Ecology Master’s student at Texas State University, he taught functional biology labs, worked as a wildlife biologist for All Out Ranch Improvements, and held an RA position conducting surveys of the Rio Grande beaver in Big Bend National Park.  Upon graduation, Joey will continue to work as a wildlife biologist for All Out Ranch Improvements.


Thesis Defense

Nutrient Limitation of Algae and Heterotrophic Bacteria in Reservoir Ecosystems:
Implications for Pelagic Competition along a Trophic Gradient

Amelia Everett

Major Advisor: Dr. Weston Nowlin       

Committee Members: Dr. Alan Groeger, Texas State University & Dr. Dittmar Hahn, Texas State University

Wednesday, April 8, 2015, 1:00 PM, FAB 130

In low productivity pelagic ecosystems with low concentrations of inorganic nutrients, bacteria have been shown to play a relatively greater role in C and nutrient cycling and the importance of bacteria is thought to decline as productivity and dissolved inorganic nutrients increases.  Plankton ecologists have proposed several mechanisms which lead to this pattern, but it is generally thought that bacteria should exhibit a competitive advantage over algae in unproductive systems with relatively high concentrations of dissolved inorganic C (DOC) and low concentrations of dissolved inorganic nutrients. However, there is a limited amount of data examining if the intensity of competition between algae and bacteria for inorganic nutrients varies with ecosystem productivity.  My thesis focused on examining the potential for competition between heterotrophic bacteria and algae across a productivity gradient in a group of 19 Texas and Ohio reservoirs. Across reservoirs, DOC:dissolved inorganic nutrient ratios decreased with increasing productivity, signifying a shift in the dominant forms of available nutrients for algae and bacteria along a trophic gradient. The N and P content of algal and bacterial cells (i.e., C:N and C:P) follow a similar pattern of increasing cellular nutrient content with increasing productivity. Concurrent nutrient limitation assays indicated that algae across reservoirs were equally likely to be primarily limited by N or P, whereas bacteria were most frequently primarily limited by P and rarely limited by C. The magnitude of nutrient limitation responses (i.e., a response ratios) were greater overall with P addition over N or C, likely due to competition for inorganic nutrients. Both algae and bacteria exhibited heightened response ratios to P than with N or C comparatively due to low concentrations of P found within unproductive systems, thus an important limiting nutrient in these reservoirs studied.

Bio:  Amelia Everett earned a B.S. in Environmental Science- Marine and Coastal Resources from Texas A&M University- Corpus Christi in 2012. While in college, she worked as a research field technician for the Conrad Blucher Institute for Surveying and Science. As an Aquatic Resources Master’s student at Texas State University, she taught general ecology labs and held an RA position conducing water quality analyses for the San Marcos River in 2014. Upon graduation, Amelia will work as a GLOBE intern for the Nature Conservancy assisting in stewardship of private lands surrounding the Pedernales and Blanco River watersheds.


Dissertation Defense

Biological and Environmental Influences on Developmental

Variation of Ungulates in Variable Environments

Daniel M. Wolcott

Major Advisor: Dr. Floyd W. Weckerly             

Committee Members: Dr. R. Terry Bowyer, Dr. Paul L. Leberg, Dr. Thomas R. Simpson, and Dr. M. Clay Green

Friday, April 3, 2015, 12:00 PM, Supple 116

 Fundamental to lifetime fitness is the amount of body development that occurs during the life of an individual. This is especially apparent in long-lived species in which age-structured populations and sexual dimorphism affect breeding success among individuals. A considerable amount of research has been conducted on ungulates in order to understand factors that affect developmental variation within populations. However, much of this work has been conducted in regions in which metabolism - and subsequently body development - is influenced by photoperiod and environmental seasonality. Recently, several studies have demonstrated that increasing environmental heterogeneity at high latitudes has negatively affected ungulate population dynamics. My dissertation focused on understanding factors that influence skeletal and somatic development of ungulates across variable environments. Specifically, I addressed developmental variation at critical life stages (natal to adulthood) and highlight new findings on body development in two species of new world cervids (Capreolinae). My dissertation demonstrated that seasonal limitations to body development, considered pervasive in ungulate populations, are less present in populations that experience benign winter conditions and higher degrees of environmental stochasticity. The new insights gleaned from this dissertation are beneficial in understanding how populations of these biologically and economically important species may adapt to changes in local climate.

Bio: Daniel M. Wolcott was born in Daytona Beach, Florida, and raised in Memphis, Tennessee. He earned a B.S. in Biology with a pre-med emphasis from The University of Memphis in 2007. He continued his education by enrolling in the M.S. program at The University of Memphis with an emphasis in ecology under the advisement of Dr. Michael L. Kennedy. Upon receiving his M.S. in 2011, he began his Ph.D. in the Aquatic Resources program at Texas State University under the advisement of Dr. Floyd W. Weckerly. His research interests are largely focused around understanding factors that affect the diversity and distribution of species. He enjoys teaching and anything related to the outdoors and family. He is thankful to his wife of 8 years, Amy, and their two children Emma (7) and Millie (2) who have been supportive throughout his education. 


Dissertation Defense

Quantification of frankiae in soil

Suvidha S. Samant

Major Advisors: Dr. Dittmar Hahn, Department of Biology, Texas State University

Committee Members: Dr. Jeffrey O. Dawson, University of Illinois at Urbana-Champaign, Dr. Mark Paschke, Colorado State University, Fort Collins, Dr. Michael Forstner, Department of Biology, Texas State University,  Dr. Bob McLean, Department of Biology, Texas State University


Friday, April 3, 2015, 8:00 AM, Supple 257

The genus Frankia represents nitrogen fixing bacteria that form root nodules with more than 200 actinorhizal plant species. In nature, Frankia is found in soil and in root nodules of specific host plants. Due to their low abundance in soil and difficulties to isolate them, most studies on Frankia focus on populations in root nodules, which are a natural locale of enrichment for Frankia. As a consequence, little is known about the ecology of Frankia in soil. This PhD. dissertation work therefore focuses on two basic objectives: (1) to develop molecular detection and quantification methods for the analyses of Frankia populations in soils, and (2) to elucidate the effects of environmental conditions on the fate of frankiae in soils. Initial work on the first objective resulted in the development of two SYBR Green based qPCR methods, using either rRNA gene sequences or nifH gene sequences as targets for the detection of all frankiae or specific subgroups in soils. Both qPCR methods are currently refined, and will finally be used to analyze Frankia populations in two studies: (1) to compare the abundance of indigenous Frankia populations in soils beneath alder and birch from 4 sites in Illinois to assess the effects of plant species and sampling location (rhizosphere, crown cover, no plant impact) on the abundance and diversity of indigenous Frankia strains, and (2) to determine variables that affect growth and abundance of specific indigenous Frankia populations in soil microcosms over time as a function of plant species and carbon resource supply. Overall, this dissertation will result in the development and application of molecular tools that will be used to increase our understanding of the fate of specific Frankia populations in soils.

Suvidha (Suvi) Samant earned a BSc. in Zoology from Carmel College, Goa, India. In 2005, she received a MSc. in Marine Biotechnology from Goa University, India, and later earned an M.S. in Biological Sciences from Wichita State University, Kansas. She entered the Ph.D. program in the Department of Biology at Texas State University in Fall 2011. As a Ph.D. student, she has been employed as an instructional assistant for Microbiology and Microbial Ecology labs.

Dissertation Proposal Defense

Population Dynamics and Habitat Conservation for the Golden-cheeked Warbler (Setophaga chrysoparia)

Adam Duarte

Major Advisor: Dr. Floyd W. Weckerly and Dr. Jeff S. Hatfield                 

Committee Members: Dr. James D. Nichols, Dr. Michael R. J. Forstner, and Dr. M. Clay Green

Friday, March 13, 2015, 2:00 PM, Supple 116

 Central to wildlife conservation and management is the ability to forecast how species will behave and persist under future environmental conditions. To accomplish this, biologists must have a deep understanding of factors that impact population dynamics for a species of interest at a variety of spatial and temporal scales. During this seminar, I will discuss my dissertation research, which is centered on updating and extending our knowledge on golden-cheeked warbler (Setophaga chrysoparia) population dynamics and habitat conservation at multiple spatial scales. Specifically, I will present papers that examine warbler habitat change, survival, immigration, productivity, and population dynamics using a variety of contemporary statistical and geospatial analyses. Using Landsat imagery, I provided quantitative evidence for a large-scale reduction in total warbler breeding habitat, which became more fragmented across the warbler’s breeding range. I estimated survival probabilities using 20 years of capture-resight data that suggest previous warbler population models were overly optimistic with respect to adult survival. Further, I found no strong evidence for spatial variation in survival or temporal patterns in survival that relate to observed warbler population dynamics. Using long-term monitoring data, I found immigration was important to stabilize local warbler populations, indicating conservation and management plans need to be implemented at a larger spatial scale. Lastly, I used these estimates to program a range-wide, spatially explicit population model to project warbler population and habitat dynamics into the foreseeable future. The model results indicated population viability could be achieved under current conditions, and that increasing the amount of protected lands would have a substantial impact on warbler carrying capacities at the end of a 50-year simulation. Overall, this research will help guide conservation decision making for the golden-cheeked warbler, at the local and range-wide scale.

Adam Duarte was raised in Wichita Falls, Texas. He earned a BS in Wildlife and Fisheries Sciences from Texas A&M University in May 2009, while simultaneously serving in the U.S. Marine Corps Reserve. In Fall 2009 he enrolled in the Wildlife Ecology MS program at Texas State University and joined Butch Weckerly’s lab. Upon completion of his Masters in May 2011 he joined the PhD program in Aquatic Resources at Texas State University, working with Butch Weckerly (Texas State University) and Jeff Hatfield (USGS Patuxent Wildlife Research Center). His research interests are focused on contributing to the effective conservation and management of natural resources through the application of modern statistical methods and geospatial analyses.

Dissertation Proposal Defense


Matthew T. Milholland

Major Advisor: Dr. Iván Castro-Arellano           

Committee Members: Dr. Joe Veech,Texas State University, Dr. Rodney Rohde, Texas State University, Dr. Tom Lee, Abilene Christian University, Dr. Gerardo Suzán Azpiri, Universidad Nacional Autónoma de México

Friday, February 27, 2015,11:00 AM, Supple 257

 Zoonotic pathogens are the dominant cause of novel and reemerging infectious diseases.  Hantaviruses (family Bunyaviridae) and their associated human diseases occur globally and differ according to their geographic distribution and type of illness exhibited in humans.  Prevention of these diseases requires surveillance of seroprevalence in animal populations.  Hantaviruses occur in close association with particular rodent, bat, and shrew reservoir hosts.  Small mammal assemblage structure and species richness are suggested as strong drivers for the maintenance and spread of hantavirus infections.  Climatic factors, such as precipitation, can influence reservoir density and abundance by increasing available food resources.  These fluctuations in rodent assemblage structure can contribute to the maintenance or reduction of hantavirus seroprevalence.  Dominance indices of competent hosts and assemblage characteristics may predict disease risk.  The research objectives of the dissertation are to:  1) to determine the ecological correlates of hantavirus prevalence in small mammal assemblages at the site, region, continental, hemisphere, and global levels; 2) to compare and contrast differences in prevalence found in sylvan and disturbed habitats; 3) investigate the relationship between phylogenetic diversity and seroprevalence; 4) to develop predictive models for hantavirus prevalence in small mammal assemblages using defined ecological correlates; and 5) to quantify transmission events and seroconversions between naïve and infected rodents.  Preliminary results suggest a relationship between the weighted site seroprevalence and the relative species abundance, observed species richness, and phylogenetic relatedness of species within the assemblage.   Current research regarding hantavirus disease dynamics usually follows outbreaks of hantaviral disease in localized areas.  My research aims at understanding the small mammal assemblage components and climatic factors influencing hantavirus prevalence, and developing a means of preventative surveillance. 

Matthew T. Milholland received his B.S. in biology in 1996 from Abilene Christian University and studied integrative physiology at The University of North Texas Health Science Center at Fort Worth before obtaining his M.S. in wildlife ecology from Texas State University in 2005.  He was a lead biologist studying the impacts of windfarms on bat and bird mortalities in Abilene, TX.  He has also worked as a contract biologist throughout Texas and as an adjunct instructor at Cisco College before beginning the Ph.D. Aquatic Resources program at Texas State in January 2013.  He and his wife of 19 years, Megan, have two children, Noah (9) and Posey (7), of whom he is very proud.


Fall 2014

Dissertation Proposal Defense

Characterization of chromatin dynamics under biotic stress in Arabidopsis

Name: Yogendra Bordiya

Major Advisor: Dr. Hong-Gu Kang        

Committee Members: Dr. Nihal Dharmasiri,Texas State University, Dr. Sunethra Dharmasiri,Texas State University, Dr. Daniel F. Klessig, Cornell University, Dr. Ping He, Texas A&M University

Friday, January 16, 2015, 10:00 AM, Supple 257-A

A genetic screen for components involved in resistance (R) protein-mediated immunity in Arabidopsis led to isolation of crt1 (compromised recognition of TCV). CRT1/MORC1 was shown to be a MORC ATPase that physically interacts with multiple immune components. While MORC1 is mainly located in endosome-like vesicles in the cytoplasm, a subpopulation resides in the nucleus, which increases after infection. The combined findings that MORC1 i) is an endonuclease, ii) is localized to heterochromatin, and iii) is implicated in epigenetic regulation, including suppression of heterochromatic transposable elements (TEs), suggest that MORC1 has an important nuclear function(s). To gain insight into the role of MORC1 in the nucleus, genome accessibility in response to Pseudomonas syringae pv. tomato (Pst) in Arabidopsis and its MORC1-associated mutants were assessed. DNase-seq, a genome-wide inspection of DNase I hypersensitive site (DHS), identified 29,450 DHS in twelve different combinations of genotypes and treatments including Pst infection. Characterization of the DHS differentially present among these different combinations revealed that genomic regions associated with signal transduction and (a)biotic stress are over-represented, under pathogen challenge. TEs were also significantly over-represented in Pst infection-induced- and MORC1 mutant-associated differential DHS (dDHS). Interestingly, these TE-associated dDHS were primarily in heterochromatic region for the MORC1 mutants but genome-wide for Pst infection-induced dDHS. Interestingly, chromatin immunoprecipitation of MORC1 showed that, while MORC1 indeed interacted with these heterochromatic TE-associated dDHS, it interacted with Pst infection-induced TE-associated dDHS that are located in well-characterized defense marker genes including PR-1 during pathogen infection. These results suggest that infection drives dynamic changes in the genome and that MORC1 plays important roles in modulating accessibility to these genomic regions. 

Yogendra received his bachelor’s degree in Agriculture from University of Agricultural Sciences, Bangalore, India in 2009 and master’s in Crop Science and Biotechnology in 2012 from Seoul National University, Seoul, South Korea. In 2012 Fall, Yogendra entered into Ph.D. program at Texas State University.

Thesis Defense


Shalini Madadi

Major Advisor: Dr. Shannon Weigum

Committee Members: Dr. Rohde, Dr. McLean

Monday, December 8, 2014 10:00 AM - Norris Conference Room

In developing countries, morbidity due to infectious diseases such as diarrheal illness can cause major deterioration of physical and cognitive impairment in young children under the age of five and individuals with poor immune system. In such regions, proper diagnosis and treatment can help in changing the mortality and morbidity rates. Current tests used to detect diarrhea-causing pathogens are often expensive, time consuming, require a well-maintained centralized laboratory with continuous power supply, highly skilled laboratory personnel and good bio-safety practices, which are often limited in resource poor settings in both developed and developing countries. Real-time PCR, immunoassays (ELISA, or EIAs, lateral-flow test strips), microscopy, and flow cytometry are few examples of traditional tests available. The goal of this project was to develop a paper-based microfluidic device for detection of Cryptosporidium and Giardia, two protozoan pathogens that cause persistent to chronic diarrhea worldwide that is inexpensive and easy to use. Toward this goal, we have designed and optimized a wax-printing technique to create microfluidic channels in paper that direct fluid flow via capillary action in defined patterns for colorimetric immunoassay detection of individual and multi-plexed pathogens. Initial results suggest that a minimum printed width of 300 µm is necessary to form an impermeable barrier in chromatography paper when heated at 95oC for 10 min, while a minimum channel width of 1500 µm is necessary to wick fluids through the microfluidic channels. Next, we performed a concentration series of immunolabeled Cryptosporidium oocysts and Giardia cysts to determine the lowest detectable number of oocysts in an enzyme-based colorimetric assay. Our results indicate that as few as 250 oocysts are detectable for Cryptosporidium and 2000 cysts for Giardia. We further fabricated 3- dimensional (3-D) paper-based devices with a size-selective filter that excludes the use of cumbersome pre-labeling protocol and expensive equipment to remove unbound-free antibodies by retaining enzyme-bound pathogens and measuring the amount of enzyme that reaches the bottom layer. Tests for size-selective membrane and 3-D retention assay using in-line filter holder proved that cellulose acetate membrane with 1.2 µm pore size had shown to retain Cryptosporidium oocysts of size 4-6 µm. Follow-up assays for detection of cryptosporidium in paper devices using enzyme retention assay showed potential for further improvement in development of paper-based microfluidic devices. This research supports the use of paper-based microfluidic assays for colorimetric detection of infectious pathogens with high sensitivity that use low cost materials and simple fabrication techniques

Bio:  Shalini Madadi was born and raised in Hyderabad, India where she pursued her bachelor’s degree in biotechnology in 2010. Coming from a developing country, she has seen the poverty and limited access to health care resources in remote areas where infectious diseases are prevalent, which inspired her to pursue a degree in master’s under the supervision of Dr. Weigum. Her research aims towards developing inexpensive and easy-to-use diagnostics that can identify infectious diseases, such as pathogens causing diarrhea, using simple colorimetric assays.


Thesis Defense



Sara E. Harrod

Major Advisor:  Dr. Clay Green             

Committee Members: Dr. Floyd “Butch” Weckerly, Dr. Thomas “Randy” Simpson

Friday, November 21, 2014 - 3:30 PM, SUPP 153A

I studied the effects of landscape characteristics on nesting success and nest site selection of native cavity-nesting birds utilizing nest boxes at the Freeman Center, San Marcos, Texas from 2013 to 2014.  Nest checks were conducted twice weekly from February to July of each year.  Landscape analyses were conducted using ArcGIS and FRAGSTATS and habitat measurements were collected on site to examine the landscape characteristics surrounding each box.  I used the Mayfield Method to estimate nest success of each nesting pair.  For each year, Principal Components Analyses (PCA) were conducted to assess characteristics of each nest box, and Canonical Correspondence Analyses (CCA) were conducted to assess relationships between habitat features surrounding nest sites and species nesting success. 

Four species utilized the nest boxes in 2013, followed by six in 2014.  In 2013, Eastern Bluebirds (Sialia sialis) (15% occupancy) and Ash-throated Flycatchers (Myiarchus cinerascens) (5% occupancy) were most successful in grassland and shrubland habitats, respectively.  Bewick’s Wrens (Thryomanes bewickii) (77.5% occupancy) were generalists; their nesting success showed no association for any habitat variable.  Sites of Black-crested Titmice (Baeolophus atricristatus) (12.5% occupancy) nests were associated with areas of little herbaceous or woody vegetative cover while no difference in landscape characteristics were found between successful and failed nests.  In 2014, bluebird (20% occupancy) success and failure were associated with large grassland patches.  Flycatcher (11.7% occupancy) success was not associated with any measured habitat variables, while failure occurred in sites with large shrubland patches.  Titmouse (38.3% occupancy) success and failure were not correlated with any measured habitat variables, while wren (71.7% occupancy) success was most likely to occur in sites with large woodland patches.  To maximize nesting success, wildlife managers utilizing nest boxes to manage for a given species should consider not only habitat types but patch characteristics such as density and area when considering where to erect nest boxes. 

Bio:  Sara Harrod was born in Wichita Falls, Texas, on October 05, 1989.  Her interest in wildlife began at a young age and led to a passion for bird-watching.  After graduating from high school, she attended Texas A&M in College Station, Texas, and began her undergraduate work.  She received a Bachelor of Science in Zoology in May of 2012.  The following fall, she began her work on her Master’s at Texas State University.  In the future Sara hopes to study the effects of anthropogenic activity on passerines and the conservation of at-risk populations. 


Thesis Defense


Cody A. Craig

Major Advisor:  Dr. Timothy H. Bonner     

Committee Members:  Dr. Christopher Taylor (UTPA), Dr. Floyd Weckerly (TxState)

Friday, November 21, 2014 - 10:00 AM,  FAB 130

Base flow is the portion of stream flow attributed to groundwater, and few studies quantify the pure effects of base flow reductions on stream fish communities. Spring complexes within the karst terrains of the Edwards Plateau Region of central Texas offer a unique opportunity to test hypothesized relationships between base flow and stream fish communities. Spring complexes are numerous within the Edwards Plateau, providing multiple independent observations, stable hydrographs dominated by base flow conditions, similar groundwater sources, and support endemic fishes that are associated with the spring complexes (i.e., spring-associated fishes).  Primary objectives of this study were to assess spring-associated fish richness, relative abundances, and densities across a gradient of base flow magnitudes with predictions that metrics of spring-associated fish communities would linearly decrease with reductions in base flow.  To control potential confounding variables, additional objectives were to test for the presence and strength of parapatry that is hypothesized to exist between spring-associated fishes and riverine-associated fishes (i.e., fishes with distributions not typically associated with spring complexes).  Patterns in richness, relative abundances, and densities indicated parapatric distribution between spring-associated and riverine-associated fishes.  Strength of parapatry depended upon base flow magnitude.  Correspondingly, differences in spring-associated fish richness, relative abundances, and densities along a base flow gradient were detected, but only densities were linearly related to base flow.  Richness and relative abundances of spring-associated fishes were non-linearly related to base flow, suggesting that spring complexes have a level of buffering capacity against base flow reductions.  The relationship between spring-associated fish communities and base flow gradient was used to support the reported parapatry between spring-associated fishes and riverine-associated fishes with in the area and to highlight the conservation value of spring complexes to regional fauna.  Predictive models generated in this study can be used to evaluate spring-associated fish community integrity within the Edwards Plateau Region and to predict future changes in Edward Plateau spring complexes related to increases in groundwater extraction.

Bio:  Cody Craig was raised in Longview, TX.  He attended Texas Tech University for his B.S. in Wildlife Fisheries Management.  Continuing his undergraduate research, he joined the graduate program at Texas State for a M.S. in Aquatic Biology.  After graduation, he would like to continue his educational pursuit with a Ph.D. with an ultimate goal of continuing research in the field of aquatic ecology.  


Thesis Defense


Melissa B. Phillips

Major Advisor:  Dr. Timothy H. Bonner (Biology)

Committee Members:  Dr. Gwendolyn Hustvedt (Fashion Merchandising), Dr. Joseph A Veech (Biology)

Thursday, November 20, 2014 - 10:00am, FAB 130

Occurrence and types of microplastics in the digestive system of freshwater fishes could be an emerging environmental crisis because of the proliferation of plastic pollution in aquatic environments.  Recent studies report increasing amounts of microplastics in marine systems and in the gut tracts of marine fishes.  To date, only one study has reported percent occurrence of microplastics (12%) in the digestive system of freshwater fishes.  Purposes of this study were to quantify occurrences and types of microplastics ingested by fishes within the western freshwater drainages of the Gulf Mexico and an estuary of the Gulf of Mexico.  My study objectives were (1) to enumerate and identify microplastics from fishes taken from 10 sites and nine freshwater drainages of Texas and harbor, bay, and gulf sites within or near the Laguna Madre of southeast Texas, (2) to compare percent occurrence of microplastics among habitat and trophic guilds of fishes, and (3) to compare percent occurrence of microplastics between urbanized and non-urbanized streams and thus test the hypothesis that fishes from urbanized streams will have greater percent occurrence of microplastics than fishes from non-urbanized streams.  Among 535 fishes examined in this study, percent occurrence of microplastics was 8% in freshwater fishes and 10% in marine fishes.  Plastic types included polyester, polystyrene, polypropylene, acrylate, and nylon. Percent occurrence of microplastics ingested by fishes in non-urbanized streams (5%) was less than that of one urbanized streams (Neches River; 29%).  Percent occurrence by habitat (i.e., benthic, pelagic) and trophic guilds (herbivore/omnivore, invertivore, carnivore) were similar.  Percent occurrences of microplastics reported herein are similar for freshwater fishes and towards the lower end of the range of microplastic ingestion in marine fishes (range: 8 - 33%).  Occurrences of microplastics in the fishes pose several environmental concerns.  For fish health, microplastics absorb toxins and can be passed through the digestive system, into the circulatory system, and accumulate in tissue.  Long-term effects are unknown for the fish or the effects on human consumers. 

Bio: Melissa Phillips was raised in London, England.  She attended the University of Leeds for her B.A. in Sociology.  After raising enough funds to she took a one way flight to Honduras where she certified as a Divemaster and dived her way around Central and South America.  Upon returning to London she worked in Marine Conservation and web development.  She enrolled in the MS-Sustainability Studies program to further a career in marine conservation, specifically to reduce the amount of plastic pollution in our marine environments.  

Dissertation Defense


Freshwater turtles as a renewable resource: using red-eared slider

(Trachemys scripta elegans) as a model species

Ivana Mali

Major Advisor: Dr. Michael R.J. Forstner            

Committee Members: Dr. Thomas R. Simpson, Dr. Floyd W. Weckerly, Dr. Scott K. Davis, Dr. Hsiao-Hsuan Wang

Thursday, November 20, 2014 - 2:00 pm LBJ 3-9.1

 Freshwater turtles have a long history of being utilized by humans. For centuries, turtles have been used as a protein resource and in traditional medicine, playing an important role in cultures across the globe. Wild turtle harvests have historically and currently been unsustainable. While some regulatory regimes have been implemented in different regions, many taxa remain unprotected and there is a need for improvement. The objective of this work was to assess the problem of unsustainable wild freshwater turtle harvest and commercial trade in the United States of America (US), focusing first on the entire southeast region and specifically on the Texas harvest paradigm. I also evaluated solutions, such as commercial turtle farming as an alternative to wild population harvest. The results provide evidence of large, unsustainable exports of freshwater turtles continuing out of the US, despite recently implemented restrictions on turtle harvest in several states of the Southeast US. Moreover, I provide evidence of the negative consequences from non-uniform harvest regimes across the Southeast US. Turtle harvest regulations in Texas are based on assumptions regarding the overland movement patterns of adult red-eared slider (Trachemys scripta elegans) on the landscape. To test these assumptions, I developed a novel method to monitor movements, achieving a higher resolution than what has been previously reported and allowed me to evaluate the source-sink harvest paradigm applied to Texas freshwater turtle populations. The results illustrate flaws in the current management regulations, but also provide direction for future studies to help improve management. Finally, by modeling biological data alongside economic information on farming red-eared sliders in Louisiana, I demonstrated the economic challenges of farming red-eared sliders for meat markets. While it gives a perspective of how the future market may develop, it highlights some of the difficulties to achieving sustainability with the commercial trade of turtles for meat.

Bio: Ivana Mali was born in Novi Sad, Serbia on February 25 1983 to Ljiljana and Petar Mali. She obtained her Bachelors of Science in Biology at Henderson State University in May 2008. She enrolled at Texas State University in 2008 and earned her Masters of Science in Wildlife Ecology in August 2010. She entered the Aquatic Resources doctoral program in 2010 focusing on chelonian population sustainability. She has been a Flowing Waters teaching fellow (2011-2013) and is the current president of the Texas Herpetological Society. Her research topics include freshwater turtle reproductive ecology, testing field sampling assumptions and biases, movement ecology, but also global freshwater turtle sustainability under anthropogenic pressures such as road mortality and commercial harvest.


Dissertation Proposal Defense

Biodiversity Research using Hierarchical Models in a Bayesian Framework

Katherine Bell

Major Advisor: Dr. Chris Nice       

Committee Members: Dr. James Fordyce, Dr. Darrin Hulsey, Dr. Noland Martin, and Dr. James Ott

November 13, 2014 - 9:00 am, LBJ Student Center 3-9.1

Biological systems are structurally complex, but hierarchical modeling allows these multiple levels of structure to be examined simultaneously. The research I propose explores the use of hierarchical models in three different biodiversity research projects: 1.) I will investigate the population genomics and genomic architecture of jaw morphology in a trophically polymorphic species of cichlid. Here a hierarchical approach will be used to model uncertainty, which results from next generation sequencing techniques, and to test for associations between phenotype and genotype. 2.) Next, I will examine the response of British butterflies to climate change.  For this question a hierarchical model will enable the simultaneous estimation of both species- and community-level responses to climate change. 3.) The third project explores the fitness surface of chemical sequestration using the pipevine swallowtail butterfly as a model system. This project will include lab and field studies which will provide data used to develop a hierarchical model that accounts for costs and benefits in fitness to both predators and prey. 

Bio: Katherine was born in Dorset, England. She received a BSc HONS in Zoology from Queen Mary, University of London in 2009. In 2010 she enrolled at Texas State University and joined the Population and Conservation Biology program, as a part of Chris Nice’s lab. Upon completion of her Masters in 2012 she joined the PhD program in Aquatic Resources at Texas State University and continued her work with Chris and the Nice lab group.


Thesis Defense




Lynsey Ramirez

Major Advisor:  Dr. Thomas R. Simpson           

Committee Members: Dr. Clay Green, Dr. Chris Nice

Monday, November 10, 2014 - 9:00 am, Norris Conference Room

Brazilian free-tailed bats (Tadarida brasiliensis) overwinter in south and central Mexico and migrate north each spring to form large breeding colonies in northern Mexico and the southwestern United States; however, there are recent observations of increasing populations of free-tailed bats overwintering in central Texas.  It is possible that climate change has led to warmer winters in northern sections of their range with increased insect productivity forming a sustainable food resource for the bats.  Dietary analysis using the dissecting microscope methodology show their summer prey includes adults of several Lepidopteran species in the family Noctuidaie and species of beetles in the order Coleoptera.  In this study I used traditional methodology of dissecting guano pellets to identify insect fragments through the use of various keys, guides and experienced entomologists, and gather information on the dietary habits of overwintering free-tails.  Pellets were collected from roosting sites at three different locations across central Texas: the Chiroptorium, Old Tunnel, and D’hanis Bridge, and then dissected in the lab.  Orders of the insects and in some cases, families, were identified which determined a glimpse of what free-tailed bat colonies are eating to survive winter months in central Texas.  Diptera, Hemerobiidae, and Lepidoptera composed the greatest percent composition of diet with significant differences between sites based on a particular food category.  Differences could be due to diverse vegetation and habitats at each sampling site.  Winter diets will begin to be established and understanding the factors that control migratory dynamics and alterations expected with continuing climate changes can be gained.

Bio:  Lynsey Martinez Ramirez was born in Alamogordo, New Mexico on August 13, 1987 to Jose and Patricia Martinez and raised in San Antonio, Texas.  She graduated with a B.S. in Biology at the University of Texas at San Antonio May of 2010 and enrolled at Texas State University-San Marcos to pursue a Master’s of Science degree in Wildlife Ecology.  Lynsey was married in 2011 and had two baby girls in 2012 and 2013.  During the course of her graduate career, she was actively involved with Hermandad de Sigma Iota Alpha, Incorporada and earned a hunting scholarship with Conservation Leaders for Tomorrow.  She was also an Instructor’s Assistant for Freshman Biology (non-majors) and a member of TriBeta National Biological Honor Society and the Texas Academy of Science.  Lynsey hopes to use her degree to pursue work in conservation biology and restoration projects.


Thesis Defense



Melissa D. Sutton

Major Advisor:  Dr. Shannon Weigum     

Committee Members:  Dr. Tania Betancourt, Dr. Dana García

Friday, November 7, 2014 - 10:00 am,  RFM 4233

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide, particularly in regions where chronic Hepatitis B and C infections are common.  Early detection of HCC remains challenging due to the lack of existing biomarkers with adequate sensitivity and specificity for screening high-risk patients.  Nanoparticle assemblies that incorporate high-affinity aptamers which specifically bind malignant hepatocellular carcinoma cells could be useful for targeted drug delivery or enhancing contrast with existing ablation therapies.  The in vitro interactions of a tumor-specific aptamer, TLS11a, were characterized in a hepatoma cell line via live-cell fluorescence imaging, SDS-PAGE and Western blotting techniques.  Cell surface binding of the aptamer-AlexaFluor®546 conjugate was found to occur within 20 minutes of initial exposure, followed by internalization and localization to late endosomes or lysosomes using a pH-sensitive LysoSensor Green dye and confocal microscopy. In an effort to characterize the TLS11a target protein, the TLS11a/AlexaFluor-546 conjugated aptamer was used in place of primary antibody in a conventional Western blot following electrophoresis and transfer of proteins extracted from various cellular components.  Prominent bands appeared just over 21 kilodaltons (kDa) in the cell surface protein fraction, the cytosolic hydrophilic protein fraction and in whole cell lysates; no TLS11a-bound protein bands were apparent in the hydrophobic membrane fraction.  Aptamer-functionalized polymer nanoparticles containing poly(lactic-co-glycolic acid) (PLGA) and poly(lactide)-b-poly(ethylene glycol) (PLA-PEG) were then prepared by nanoprecipitation and passively loaded with the chemotherapeutic agent, doxorubicin, yielding spherical nanoparticles approximately 50 nm in diameter.  Targeted drug delivery and cytotoxicity was assessed using live/dead fluorescent dyes and a MTT colorimetric viability assay with elevated levels of cell death found in cultures treated with either the aptamer-coated and uncoated polymer nanoparticles.  Identification and characterization of the cell surface protein epitope(s) recognized by the TLS11a aptamer are ongoing along with nanoparticle optimization, but these preliminary studies support continued investigation of this aptamer and functionalized nanoparticle conjugates for targeted labeling and drug delivery within malignant hepatocellular carcinomas.

Bio:  Melissa Sutton was raised in Virginia Beach, Va. and moved to Texas in 2008.  She briefly attended Austin Community College where she received her A.S. in Chemistry, before transferring to Texas State for her B.S. in Microbiology.  Continuing her undergraduate research, she joined the graduate program at Texas State for a M.S. in Biology.  After graduation, she would like to have a career in industry, either working in a lab or a research facility.


Thesis Defense


Effects of diel cycle and turbidity on antipredator response to multiple cues of predators by Eurycea nana and Eurycea sosorum.

Kristina Zabierek

Major Advisor:  Dr. Caitlin Gabor           

Committee Members: Dr. Jim Ott, Dr. Kristen Epp

Friday, October 31, 2014 - 1:30 pm, SUPP 153-A

Predation is an influential force in many ecological communities. Prey often exhibit antipredator behaviors which minimize risk of predation. However, antipredator behavior may be costly by reducing time spent foraging or mating. I wanted to determine whether Eurycea nana, the San Marcos salamander, is able to minimize costs of antipredator behavior by responding to chemical cues of predators based on the diel cycle of the predator. I studied response of salamanders to a diurnal predator, green sunfish (Lepomis cyanellus) and a nocturnal predator, red-swamp crayfish (Procambarus clarkii) during the daytime and nighttime to determine if salamanders were able to respond in a risk-sensitive manner. I found that salamanders exhibited increased antipredator behavior in response to green sunfish, but not to crayfish. I also found that diel cycle did not affect antipredator behavior, suggesting they do not respond in a threat sensitive manner based on the foraging cycle of their predator.

            Anthropogenic influences can have effects on predator-prey interactions. Increased turbidity is a growing problem for aquatic systems and can affect the ability of prey to respond to predators. I studied the effect of turbidity on antipredator behavior in Eurycea sosorum, the Barton Springs salamander, by comparing their response to cues from green sunfish predators, Lepomis cyanellus, and green-throat darter non-predators, Etheostoma lepidum. I wanted to determine whether multimodal cues are important in predator detection, therefore cue treatments included a fully crossed design including both chemical and visual cues of the predator and non-predator across two vision levels; clear (0 NTU) and low turbidity (~20 NTU). I found that E. sosorum significantly increased antipredator behavior to predator chemical cues compared to non-predator chemical cues but did not respond to visual cues. This suggests multimodal cue use is not a major factor in predator detection. We also found that E. sosorum had decreased antipredator behavior in turbid conditions compared to clear conditions. This has significant conservation implications for the already endangered salamander.

Bio: Kristina was raised in Brooklyn, New York and received her B.A. in Biology at CUNY Queens College in 2012. During her time there she worked in a research laboratory studying costs of pesticide resistance in the Colorado potato beetle. She spent a summer on a farm in Ithaca, NY studying organic farming methods to attract natural predators of the Colorado potato beetle. Interested in conservation, Kristina also had an internship with the NYC Parks Department monitoring piping plovers. Always being interested in amphibian biology, Kristina joined the Population & Conservation Biology under Dr. Gabor in 2013. During her graduate education Kristina participated in projects examining anthropogenic effects on stress hormones (CORT) in Eurycea nana and Eurycea tonkawae. After completion of her M.S. degree, Kristina plans to dedicate herself to pursuing knowledge about insect-amphibian interactions and to conservation education.


Thesis Defense


The impact of human disturbance on the foraging ecology of Green Herons (Butorides virescens)

Amanda A. Moore     

Major Advisor:  Dr. M. Clay Green

Committee Members: Dr. David Huffman, Dr. Thomas “Randy” Simpson

Friday, October 31, 2014 - 10:00 am, RFM 4233

As the trend towards urbanization continues, natural areas can become highly urbanized and recreational use of these natural areas may also increase. Waterbirds use areas that are generally subject to elevated levels of human disturbance and consequently are often considered highly susceptible to disturbance. In 2013 and 2014, I assessed the effects of human recreational disturbance on Green Herons (Butorides virescens) through the use of focal observations. I collected behavioral data over 154 observations along the headwaters of the San Marcos River located in Central Texas; the river varies in its degree of human recreational activity and thereby disturbance varied across sites. I built 15 linear regression models to assess the potential influence of human disturbance as well as potential influence of habitat differences between study sites on each of the response variables (4 foraging behaviors and foraging efficiency).

Using AIC model selection, I found that differences in habitat provided the best explanation for the observed variation in 4 of the 5 response variables measured. These results suggest that Green Heron foraging behavior is not significantly affected by human recreational disturbance but influenced more by differences in habitat. It is possible that the birds are habituated to disturbance and tolerant of humans at certain locations and perhaps only modify their foraging technique in order to maximize their foraging efficiency to suit their locale. These finding are noteworthy in that it is important to be able to distinguish cases where human disturbance impacts a species from cases where it does not in an ongoing effort to strike a balance between the needs of waterbird species and human recreational use of aquatic systems.

Bio: Amanda Moore was raised in Bloomingdale, Illinois and moved to Texas in 2001. She received a B.A. in Arts & Technology from U.T. Dallas in 2005. After graduation, Amanda worked out in the “real world” for about 5 years before deciding to change paths and move to San Marcos to join the Texas State Wildlife Ecology graduate program. She hopes her next “real world” career involves conservation, fieldwork, and birds.


Thesis Defense

Floral Scent Production in the Carrion Flower Genus Stapelia (Apocynaceae)

Johann Souss

Major Advisor: Dr. David Lemke             

Committee Members: Dr. Michael A. Huston, Dr. Garland Upchurch

Thursday, October 30, 2014 - 1:00 pm, Norris Conference Room

            Floral scent plays an important role in the reproductive biology of many flowering plants, often serving as a pollinator attractant. In a majority of species, floral scent is a diffuse product of the epidermis, especially that of the corolla. In some groups, however, the production and emission of the volatile substances responsible for fragrance is localized to specialized glands, temed osmophores. This study examined the composition of floral fragrance in the genus Stapelia, a group of succulent perennial herbs native to the drier regions of South Africa. Volatile compounds produced by flowers were collected using headspace-solid phase microextraction. Component separation and identification were achieved using gas chromatography-mass spectrometry. A diversity of organic compounds was found among members of the genus, including various terpenoids, organic acids, sulfur compounds, and nitrogenous compounds. Among the most common compounds identified were dimethyl disulfide, dimethyl trisulfide, hexanal, and trimethylamine. Although osmophores were originally described from the petals of other members of the milkweed family, this study has demonstrated, using a combination of vital staining, histological examination, and gas chromatography, that among Stapelia species the production of volatile compounds appears to be a function of the corona, the often elaborate set of appendages situated between the corolla and androecium.

Bio: Johann Souss received his B.S. in zoology from University of Florida in 2008.  Upon completing his undergraduate degree he worked as a resident naturalist in Costa Rica.  He joined the Texas State biology graduate program in 2010.  He moved to Oregon in 2012, where he spent most of his time exploring his interests in coffee and hospitality.  Johann will be departing for Tanzania in February 2015 to work on sustainable agriculture and environmental education projects as a Peace Corps Volunteer.



Thesis Defense

Examining the effects of urbanization on the occurrence of mammal species

in natural areas of the eastern Edwards Plateau


Matt Haverland

Major Advisor:  Dr. Joe Veech           

Committee Members: Dr. Butch Weckerly, Dr. Jennifer Jensen (Geography)

Thursday, October 30, 2014 - 10:30 am, Norris Conference Room

Central Texas is experiencing urbanization at an unprecedented rate. This anthropogenic conversion of land is due in part to a rapidly growing population in the Austin and San Antonio metro areas and the development of infrastructure and resources needed to support that growth. Urban parks, greenspaces, and preserves can mitigate the impact of land development by serving as habitat for local wildlife populations. To maximize the potential of this habitat, we must assess how urbanization influences species across a landscape. Mesocarnivores act as top-tier predators in an ecosystem almost completely devoid of large predators and thus they could influence abundance of other species. I surveyed 72 sites (point locations) across nine different study areas throughout the eastern Edwards Plateau ecoregion of central Texas for fourteen survey occasions during 2013. Using occupancy modeling, I examined the influence of ten different urban covariates on mesocarnivore occurrence. Generalist species, such as raccoons and opossums, had an increased probability of occurrence at sites with higher urban influence and were most likely to occur in smaller more urban study areas. Ringtails and grey foxes appeared to be unaffected by urbanization and were equally likely to occur across all sites. Results for other species, such as the coyote and skunk, were inconclusive. Most species had very low probability of detection with only the raccoon and fox having a probability greater than 0.1.  Knowledge of the effect of urbanization on wildlife could assist us in evaluating current preserves as well as devising strategies to conserve species in any planned future preserves.

Bio: Matthew Haverland was raised in College Station, Texas and received his B.S.  in Marine Fisheries at Texas A&M University-Galveston in 2007. During his time in Galveston, he worked as a student research assistant for the NOAA Fisheries Ecology Lab aiding biologists in studies on benthic marsh communities in Texas and Louisiana. After graduation, Matt joined the NOAA Fisheries Service as a temporary fisheries observer collecting data on bluefin tuna spawning in the Gulf of Mexico and later joined the Pelagic Observer Program as a full time fisheries observer where he worked for several years. After a renewed interest in terrestrial biology, Matt joined the Texas State Wildlife Ecology graduate program in 2012. During his graduate education, Matt has participated in several ecological studies including work as a seasonal field technician conducting bobwhite quail surveys. After completion of his M.S. degree, Matt plans to seek employment as an ecologist examining vertebrate communities and ways to mitigate the impact of human development.


Dissertation Proposal Defense


Probiotic regulation of fat-storage via Angiopoietin-like 4 (ANGPTL4)

  Priscilla Pham

  Major Advisor:  Dr. Bob McLean           

  Committee Members: Dr. Dana García,  Dr. Shannon Weigum, Dr. Dhiraj Vattem,

  Dr. Jennifer Spinler, Dr. Vatsala Maitin

  October 17, 2014 - 11:00 am, SUPP 153-A

Gut bacteria have been shown to influence diet-related obesity, mediated in part via ANGPTL4, a       circulating lipoprotein lipase inhibitor that modulates fat-storage in the adipose tissue. Modulating the gut microbiota to exert stimulatory activity towards ANGPTL4 may thus serve a protective function against diet-related obesity. I have screened several commonly used probiotic strains for enterocytic ANGPTL4-modulation in vitro and observed significant increases in ANGPTL4 protein levels in response to secreted factors from Bifidobacterium longum. An initial characterization of these bioactive factors indicated them to be secreted B. longum proteins. The objective of the proposed study is to further elucidate the mechanism of ANGPTL4-regulation by B. longum and its impact on fat storage, and investigate if dietary enrichment of Bifidobacterium in the gut can enhance ANGPTL4 in human subjects.

Bio:  Priscilla Pham is from Houston, Texas and received her BS in Human Nutrition and Foods from Prairie View A&M University. In 2010, she entered the Master’s in Human Nutrition Program at Texas State University and began her research in the Molecular and Cellular Nutrition Laboratory under Dr. Vatsala Maitin. As a PhD student, she is continuing her research work under the advisement of Dr. Bob McLean.


Thesis Defense

Species traits versus environmental properties as factors

influencing species abundance

Stephanie Miller

Major Advisor:  Dr. Joe Veech           

Committee Members: Dr. Jim Ott, Dr. Ivan Castro-Arellano

Tuesday, October 21, 2014 - 12:30 pm, SUPP 257-A

A longstanding goal in ecological research is to explain the abundance of a species found in a particular place and time. To do so, researchers identify factors that influence species abundance and attempt to describe their relationships quantitatively. The main objective of my study was to compare the relative effects of intrinsic species traits (morphological, physiological, behavioral and life history attributes) and extrinsic environmental properties (climatic, biotic and geographic aspects) on species abundance. From a literature search, 915 independent abundance observations were compiled for 83 species from 170 survey locations distributed throughout the western United States. Besides abundance information, data on species traits associated with body size, reproductive capacity, diet, and geographic range were acquired along with properties of each survey location including climatic, spatial, and biotic (number of other rodent species and individuals) variables. To make the comparison, four composite variables (an intrinsic ecological variable, intrinsic geographic variable, extrinsic abiotic variable and extrinsic biotic variable) were created using Principal Components Analysis (PCA), and a fifth variable that was the distance between each species location (occurrence in a particular survey) and the center of that species geographic range was also included. Model comparison and model-averaging procedures were then conducted using all 31 possible linear regression models of the five predictor variables with standardized abundance (corrected for extraneous design variables) as the response variable. For the dataset consisting of all species, the intrinsic ecological variable was found to have the greatest influence on abundance (N=915, βeco = 0.116, SE= 0.042). For datasets limited to certain genera (Dipodomys, Neotoma, Perognathus, and Peromyscus), different variables were identified as most influential. These results indicate that environmental properties and species traits can influence abundance independently and in combination with one another. Moreover, there is no single combination of extrinsic and intrinsic variables that most influences abundance in all genera. Nonetheless, the distinction between intrinsic and extrinsic variables is a useful dichotomy in studying the factors affecting species abundance.

Bio: Stephanie received her Bachelors of Science from the University of Florida in 2010, with a major in Zoology and a minor in Wildlife Ecology and Conservation. During her undergraduate career she worked in a physiology lab studying the response of snake kidneys to salinity changes and an animal behavior lab that studied the effects of predation on cichlid parenting structure. Upon completing her undergraduate degree, Stephanie acquired a field technician position working for a Clemson University Ph.D. student examining the habitat use of coyotes and raccoons on Yawkey Wildlife Preserve. Now after completing her Masters at Texas State University in Population and Conservation Biology, she plans to continue her education studying topics at the intersection of community ecology, species distribution, and biodiversity conservation.

Dissertation Proposal Defense

Personality, predation, and competition in a changing environment

Chelsea Blake

Major Advisor: Caitlin Gabor , Biology Department, Texas State University             

Committee Members: Dr. Andrea Aspbury, Biology Department, Texas State University, Dr. Alison Bell, University of Illinois-Champagne-Urbana, Dr. Brian Langerhans, North Carolina State University, Dr. Chris Nice, Biology Department, Texas State University  

Sept 4, 2014 - 12:00 noon, HPB 145

 In order to explore the effects of anthropogenic environmental change on the behavioral ecology of native species, I propose four studies which will examine a range of predatory and competitive relationships. I present a study examining how personality of native prey individuals influences their behavior and survival of several different predator species, including native, novel, and invasive predators. In a second study, I will examine the relationship of behavioral traits to body shape traits associated with predator escape ability, and plasticity of behavior in response to morphological changes. I will also explore how personality of prey may relate to predator recognition in response to a novel predator. In the final study I will explore how environmental changes like rising turbidity can interact with competitive and predatory relationships among native species. The goal of the experiments presented is to add to our understanding of how behavior interplays with anthropogenic changes to shape outcomes for native species in shifting ecological landscapes.

Bio: Chelsea Blake grew up in the heart of the Midwest. Chelsea double majored in Art and Biology at Earlham, a Quaker liberal arts college in Indiana. After gaining teaching, field work, and research experience in Maryland, Oregon, Georgia, and South Carolina, she moved to Texas in 2011 and entered the Aquatic Resources PhD program at Texas State. She received a National Science Foundation Graduate Research Fellowship in 2013 to support her dissertation work. She lives in Austin with a houseful of pets, roommates, and her husband. She legally married her partner (and best field assistant) while in New York this summer.



Summer 2014

Thesis Defense


The effect of indole production on the growth of Escherichia coli when co-cultured with Enterococcus faecalis

Shelly L. Pringle

Major Advisor: Dr. Robert JC McLean

Committee Members: Dr. Gary Aron, Department of Biology, Dr. Dittmar Hahn, Department of Biology, Dr. William Coons, Department of Biology, Victoria College

July 11, 2014 - 2:00 pm, SUPP 257-A

In nature, bacteria live in dynamic communities surrounded by a vast number of other bacterial species. Recent studies indicate that one mechanism by which Escherichia coli thrives within such a multitude is via production of the molecule indole. Evidence indicates that indole thwarts the quorum sensing system of acyl-homoserine lactone (AHL) producing bacteria such as Pseudomonas aeruginosa, Chromobacterium violaceum, and Pseudomonas aureofaciens. Impeding the signaling system of these bacteria ultimately leads to a lowering of toxic secretions such as pyocyanin and proteases. The aim of this research was to determine if the production of indole by E. coli increases its competitive fitness with Enterococcus faecalis. E. faecalis is a Gram positive, non-AHL producing bacteria which is found alongside E. coli as normal flora in the human intestine, as well as  in a number of mixed culture infections. E. faecalis has increasingly become a concern as it is now a leading cause of hospital-acquired infection and has developed resistance to “last-line” antibiotics such as Vancomycin. Colony counts and turbidity of ΔtnaA (the E. coli mutant incapable of degrading tryptophan and thus deficient in indole production) were measured in mixed culture with E. faecalis. Indole was then reintroduced at physiologically relevant concentrations. Contrary to previous research, in competition with E. faecalis the population size of E. coli is inhibited and indole has a further inhibitory effect.


Shelly Pringle attended the University of Texas where she received a Bachelor of Arts in Biology in 2003.  Upon receiving her degree she worked as a high school science teacher, teaching Biology, Chemistry, and Integrated Physics and Chemistry. In the fall of 2012, Shelly was admitted to Texas State University–San Marcos to pursue a Master of Science in Biology.


Thesis Defense

Seasonal diets of the collared peccary (Pecari tajacu)

In the Llano uplift ecological region of Texas

Meredith Hominick

Major Advisor: Dr. Thomas R. Simpson             

Committee Members: Dr. M. Clay Green, Department of Biology, Dr. James F. Gallagher, Department of Biology

July 07, 2014 –1:00 pm, SUPP 153-A

I investigated the seasonal diets of the collared peccary (Pecari tajacu) at Mason Mountain Wildlife Management Area from June 2013 to April 2014 using microhistological analysis of fecal material.  Eighty fecal samples were collected from summer 2013 to spring 2014.   I identified and quantified 36 plant species consumed by the collared peccary. Prickly pear was consumed in all seasons with seasonal use of forbs, grasses and mast.   Annually, the bulk of the diet was comprised of browse (including prickly pear) 37.1%, forbs 32.8%, mast 22.4% and grasses 7.8%.  Primary browse species included prickly pear (Opuntia spp.) and live oak/blackjack/post oak (Quercus spp.).  Forbs, especially silver bladderpod (Lesquerella argyraea) and prickly fanpetals (Sida spinosa), were highly utilized as well.  Vegetational surveys were conducted using the Daubenmire method to sample herbaceous species and line intercept method to sample woody species.  Results of log-likelihood chi-square tests with Bonferroni corrected confidence intervals established that there were statistically significant differences between plant use and availability (P<0.001). Additionally, Manly’s alpha preference indices indicated that collared peccaries foraged selectively on silver bladderpod in spring. Prickly pear was a selected food plant in the summer. Peccaries selectively foraged on live oak/blackjack/post oak and prickly pear in the fall and selected prickly fanpetals during winter.

Meredith received a B.S. in Biology and a minor in Environmental Science from University of the Incarnate Word in 2012. She began her studies at Texas State in the fall of 2012, and completed internships with Texas Parks and Wildlife Department as well as Bayou Land Conservancy.


Thesis Defense


Detection of Borrelia burgdorferi sensu lato Infection in Rodents
From Disturbed and Sylvan Assemblages Across Texas

Troy J. Maikis

Major Advisor: Dr. Iván Castro-Arellano, Department of Biology, Texas State University

Committee Members: Dr.Thomas R. Simpson, Department of Biology, Texas State University, Dr. Maria Esteve-Gassent, Department of Veterinary Pathobiology, Texas A&M University

July 3, 11:00  Norris Room, Supple Science Building

Lyme disease, caused by the bacterium Borrelia burgdorferi, affects tens of thousands of Americans each year.  Most of the research in the United States is conducted in the northeastern portion of the country.  Texas represents an under-studied area with low incidences of annual human infection.  Studying the bacterium in an area of low incidence could answer questions about why it has a greater prevalence in other parts of its range.  The present study investigated tick loads on rodents and Borrelia prevalence in disturbed and sylvan habitats at five sites in Texas across three seasons.  At four of the sites investigated, rare and relatively large bodied species that were only captured in sylvan habitats had  higher tick load than the rest of the species collected at the site.  Borrelia prevalence was found to vary seasonally, with larger numbers of infected individuals being captured in the fall.  Future studies are needed to determine if the results described herein represent a consistent pattern, but this work represents a positive step toward investigating LD in the southern portion of its range.

Bio:  In 2006, Troy Maikis graduated with a B.S. in Ecology and Evolutionary Biology from The University of Arizona.  After receiving his degree, Troy went on to work all across the western U.S. for multiple government agencies, non-profits, and private contracting firms.  In the fall of 2012, he began his M.S. research at Texas State University.  Following the first presentation of a portion of his M.S. research, Troy was awarded the William B. Davis award by the Texas Society of Mammalogists.


Thesis Defense

Reliability Analysis of Rainwater Harvesting in Three Texas Cities

Name: Dustin Lawrence


Major Advisor: Dr. Vicente L. Lopes, Dept. of Biology             


Committee Members: Dr. Walter Rast, Dept. of Biology, Dr. Ronald R. Hagelman, Dept. of Geography

July 2, 2014 10:00am FAB 130

Population growth and a prolonged drought have raised concerns about the sustainability of water resources in Texas. Recent state legislation has made financial assistance available towards the development of water supplies. The purpose of this research is to inform decision makers at state and local levels, as well as property owners about the amount of water that can be supplied by rainwater harvesting systems in Texas so that it may be included in any future planning. Reliability of a rainwater tank is a concern as people want to know to what degree a source of water can be depended on. Performance analyses were conducted on 3 cities under different climate conditions and multiple scenarios to demonstrate the importance of optimizing rainwater tank design. This was accomplished using a daily water balance model and running simulations on a range of tank sizes appropriate for rainwater harvesting at the household level. Reliability curves were produced and reflect percentage of days in a year that water can be supplied by a tank. Operational thresholds were reached in all scenarios and mark the point at which reliability increases by only 2% or less with an increase in tank size. Maximum thresholds were also reached in some scenarios and indicate a tank size that provides the maximum achievable reliability. Additional simulations considered several average years of rainfall for each city under a single scenario to determine an average ideal tank size. A payback period analysis was conducted on these tank sizes to determine the amount of time it would take to recoup the cost of installing a rainwater harvesting system.

Bio: Dustin Lawrence was raised in New Braunfels, Texas.  After serving for 4 years in the United States Army, he received a B.S. in Geography with a minor in Biology from Texas State University in 2010. He was accepted into the Aquatic Resources program at Texas State University as a Master’s Candidate in 2011. While working towards his graduate degree, he taught 2 semesters of biology labs, interned with the Texas Commission on Environmental Quality, and started a family. He currently works full-time as a laboratory technician for New Braunfels Utilities conducting various tests to maintain water quality standards.


Thesis Defense

Validating environmental flow recommendations:

drifting coarse particulate matter, invertebrates, and larval fishes

Christopher R. Vaughn

Major Advisor: Dr. Timothy H. Bonner, Department of Biology

Committee Members: Dr. Floyd W. Weckerly, Department of Biology, Dr. Archis Grubh, Texas Parks & Wildlife

July 3, 2014 – 1:00 PM, Freeman Aquatic Building (FAB) 130

Water quantity management in Texas and elsewhere is currently managed under the theory of the Natural Flow Paradigm, which states that sound ecological riverine environments are dependent upon the dynamic character of flow.  Water quantity recommendations and standards prescribe a multi-tier flow regime, consisting of subsistence, base, and high-flow pulses, with magnitudes of each based on long-term averages of site-specific hydrographs.  The next step in water quantity management is to validate that the recommended flow regimes are sufficient to maintain a sound ecological environment, although validation methodologies are rarely incorporated into water quantity management plans.  Purposes of this study were to develop methodologies for validating flow recommendation and standards that are transferable and replicable and to quantify the value of flow tiers relating to organic drift.  Objectives of this study were to assess drift biomass of coarse particulate matter (CPM) and drift rates of invertebrates and larval fishes related to flow tiers (i.e., subsistence, base, two per season high flow pulse, one per season high flow pulse, and one per year high flow pulse) across four sites and two rivers (i.e., San Antonio and Guadalupe rivers).  A priori predictions were that CPM, invertebrates, and larval fishes were in greater biomass or densities at higher flow tiers, though at some point flows would be sufficiently high and induce a washout effect.  Findings were generally inconsistent with the predications.  Biomass of CPM did not differ among flows ranging from subsistence to two per season high flow pulse events, and densities of macroinvertebrate did not differ among flows ranging between base and one per season events.  However, densities of fluvial specialist Neoperla (Order Pelcoptera) were positively correlated with flow as a continuous variable rather than a categorical variable.  Densities of larval fishes were greatest at subsistence, base, and two per season high flow pulses and decreased at 1 per season flow pulses.  It is uncertain if a washout effect occurred or if survival of larval fishes was decreased at a higher flow pulses.  With a validation methodology in place, replications from other sites and river basins can be added to the existing model to improve statistical power and inference, along with other flow-dependent variables, in order to fully assess the value of multi-tier flow regimes.    

Christopher Vaughn is from Arlington, Texas.  He attended Texas A&M University where he received a Bachelor of Science in Wildlife and Fisheries Sciences with an emphasis in Fisheries Ecology and Conservation in December 2011.  Immediately upon graduation, Christopher came to Texas State University to earn his Masters of Science degree in Aquatic Resources.  His primary area of research is in instream flow, water quantity management, and the effects that deviant flows have on instream biota, in particular, drifting organics.


Thesis Defense


Atmospheric Carbon Dioxide and its Relation to Carbon Cycle Perturbations during Ocean Anoxic Event 1d: A High Resolution Record from Dispersed Plant Cuticle

Name: Jon D. Richey

Major Advisor: Dr. Garland R. Upchurch

Committee Members: Dr. David E. Lemke, Dept. of Biology, Dr. Noland H. Martin, Dept. of Biology, Dr. Marina B. Suarez, Dept. of Geological Sciences, University of Texas – San Antonio  

 July 3, 2014 10:00am Supple 153-A

Past geological greenhouse intervals are associated with Ocean Anoxic Events (OAEs), which result from an increase in marine primary productivity and/or an increase in the preservation of organic matter. The end point is widespread black shale deposition combined with a long-term atmospheric positive δ13C excursion from an increase in the burial of 12C. Some OAEs show a negative δ13C excursion preceding the positive excursion, indicating a perturbation in the global carbon cycle prior to the initiation of these events.

The Rose Creek Pit (RCP) locality, southeastern Nebraska, is currently the only known terrestrial section that preserves OAE1d (Cretaceous, Albian-Cenomanian Boundary) and has abundant plant organics. These features allow for a combined analysis of carbon isotopes and stomatal index (SI) to determine changes in the cycling between carbon pools and their relation to inferred paleo-CO2. To do this, RCP SI data were calculated from the cuticle of Pandemophyllum kvacekii (an extinct laurel) and related taxa, and fitted to δ13C curves derived from fossil gymnosperm charcoal and lignitized wood, as well as other published δ13C profiles from RCP and nearby sediment cores. Absolute values of CO2 were estimated using three published transfer functions based on species of extant Lauraceae.

SI indicates changes in CO2 coincident with changes in δ13C.  Near the bottom of RCP, pCO2 was relatively low (330−615ppm). At the same level, this study records a negative δ13C shift of ~2.8−2.96‰ compared to pre-excursion samples collected near RCP, similar to that of other RCP δ13C curves (~2.14−2.4‰). All RCP δ13C curves show that the negative excursion lasts through ~3.3m of the section. During this negative excursion, pCO2 increases from the pre-excursion values to a high of ~380−800ppm. After the negative excursion, all RCP δ13C curves and pCO2 values show a slow return to pre-excursion values. Despite the finer sampling intervals of this study compared to other RCP δ13C curves, δ13C curves from fossil gymnosperm charcoal and lignitized wood do not record the positive excursion recorded in carbonate δ13C curves during OAE1d. This study confirms that δ13C of fossil wood, whether coalified or charcoalified, and SI from dispersed cuticle can reliably capture carbon cycle perturbations and changes in atmospheric CO2 around OAEs.

Bio: Jon D. Richey was raised in Tyler, TX. After a long break from higher education, he received a B.S. in Biology from Texas State University – San Marcos in 2011, and entered into the Master’s program in Biology that same year. Jon received a National Science Foundation Graduate Research Fellowship in 2013 and a Texas State Thesis Support Fellowship in 2014. He will enter the Ph.D. program in Earth and Planetary Sciences at the University of California – Davis Fall 2014.


Thesis Defense

Variation in rumen-reticulum fill in white-tailed deer (Odocoileus virginianus)

Meredith R. E. Aiken


Major Advisor: Floyd W. Weckerly            

Committee Members:Dr. Thomas R. Simpson, Department of Biology, Dr. M. Clay Green, Department of Biology

June 24, 2014 – 11:00 AM, Supple 153

Understanding variation in rumen-reticulum fill allows us to predict how ruminants will accommodate fluctuations in food supplies and animal production demands. Studies suggest rumen-reticulum fill increases with lower quality diets (low crude protein-CP, high acid detergent fiber-ADF) and browse diets compared to pelleted diets. Rumen-reticulum fill presumably fluctuates with the demands of antler growth and access to females during the mating season, in male white-tailed deer, and during late gestation and lactation in females. Previous research has mainly examined the relationship between rumen-reticulum fill and body mass; however, multiple factor may be influencing rumen-reticulum fill. Herein, I examined the influences of nutrition (ADF and CP), diet type (pelleted or browse), reproductive demands (males in rut vs. males outside of rut, lactating vs. non-lactating) as well as body mass, rump fat, age, and sex on wet and dry rumen-reticulum fill. I collected white-tailed deer (122 males, 152 females) from Kerr Wildlife Management Area, Texas (pen-raised, free ranging) and a private ranch in south Texas. I built models and used Akaike Information Criteria to select competing models to understand which hypotheses explained rumen-reticulum fill dynamics. The only prediction that was not falsified was that lactating females had greater fill. In regards to nutrition, wet fill decreased, as ADF increased. This is likely because of chemostatic factors that regulate food intake and diet quality when dietary fiber is ‘low’. Deer consuming a pelleted diet had greater wet and dry rumen-reticulum fill than deer consuming a browse diet. My findings indicate that scaling relationships between body mass and rumen-reticulum fill were allometric. Additionally, rumen-reticulum fill is influenced by a wide variety of factors.

Meredith received a B.S. in Wildlife and Fisheries Science from Texas A&M University in 2009. She began her studies at Texas State in the fall of 2012, and was recently awarded the Leadership Scholarship from the Max McGraw Wildlife Foundation and Wildlife Management Institute.



Thesis Defense

Current velocity and flow mediated diets of larval fishes

David S. Ruppel

Major Advisor: Dr. Timothy H. Bonner

Committee Members: Dr. Floyd W. Weckerly, Department of Biology, Dr. Alan W. Groeger, Department of Biology

June 12, 2014 – 12:30 PM, FAB 130

Purposes of this study were to test two theories relating to food consumption of larval stream fishes.  Flow-pulse feeding theory states that larval fish food consumption will be greater following nutrient-rich flow pulses.  Drift-feeding theory states that larval fishes enter the drift at night to consume food items under the protection of darkness.   Objectives of this study were to quantify gut fullness and occurrence and abundances of food items consumed among larval fishes taken during subsistence flow, base flow, and several high flow pulse tiers (e.g., one per season, one per year) and between larval fishes taken during the day in slackwater habitats and larval fishes taken during the night in swift water habitats.  During one year period of observation among four sites and two rivers, mesolarval of obligate riverine taxa (i.e., Cyprinidae, Catostomidae, Percidae) had greater gut fullness within 28 d following a 1 per season flow event than those taken within 28 d following subsistence flow, base flow, 2 per season flow event.  Greater gut fullness during a 1 per season flow event was attributed to greater numbers of copepods and organic detritus consumed.  However, gut fullness and occurrences and abundances of food items consumed by metalarvae were independent of flow.  Among mesolarvae and metalarvae collectively and among taxa, gut fullness was greater during the day for fishes taken in slackwater habitat than those taken at night from swift water habitats.  Larval fishes within lowland rivers of western gulf slope drainages of Texas conformed only partially to larval fish feeding theories.  Drift-feeding theory likely is not a mechanism to explain larval drift at night, and the value of flow pulses to larval fish feeding and subsequent recruitment was not consistent among larval life stages.   Nevertheless, this study documents for the first time larval fish food consumption in lowland rivers and establishes a process to quantify the value of flow tiers relevant to the stream fish community.

David received a B.S. in Zoology from Northern Michigan University in May 2012. David began his studies at Texas State University in Summer 2012 and was recently awarded the Certificate of Excellence in Spring 2014.  David currently serves as President of the Aquatic Biology Society and is a member of the Texas Chapter of the American Fisheries Society. 


Spring 2014

Thesis Defense


Daniel C. Huston

Major Advisor:
Dr. David G. Huffman

Committee Members:
Dr. Ivan Castro-Arellano, Department
Dr. Kenneth G. Ostrand, U.S. Fish and Wildlife Service

May 8, 2014 – 1:00 PM, Supple 116

Centrocestus formosanus and Haplorchis pumilio are invasive Heterophyid trematodes which have been introduced to Texas via introductions of their first intermediate snail hosts. Second intermediate hosts for both of these trematodes include multiple species of freshwater fishes, which become infected when exposed to free-swimming trematode cercariae. Centrocestus formosanus cercariae encyst in the gills of their fish hosts, whereas H. pumilio cercariae penetrate the epidermis and encyst in the head and tissues of the fin insertions. Though mortalities in fish hosts have been attributed to these trematodes in artificially confined systems such as fish culture, there are no reported fish kills attributed to these trematodes in the wild. We speculate that many fish species restricted to stable spring-fed systems would experience increasing parasite burdens of these trematodes over time. High metacercarial intensities in the gills could lead to reduced respiratory efficiency, while high metacercarial intensities in the fin insertions could reduce swimming performance. In order to test this hypothesis and estimate the impact of these parasites, we developed a methodology for the artificial infection and swimming endurance testing of small fish hosting various intensities of trematode metacercariae. We found we were able to induce a wide range of metacercarial intensities in our fish using wild caught Melanoides tuberculata infected with either C. formosanus or H. pumilio, and that we could test the swimming endurance of these fish with a specially constructed swim tunnel. This methodology has laid the groundwork for the development of a mathematical model of the impact of these parasites at various metacercarial intensities. In addition, we utilized artificial infection methods to examine host specificity for C. formosanus. Though C. formosanus has previously been reported to infect frogs and toads in Asia, the potential for Texas amphibians to become infected has been ignored. We exposed adult San Marcos salamanders (Eurycea nana) and larval leopard frogs (Lithobates berlandieri) to the cercariae of C. formosanus. We found that while the neotenic E. nana was refractory to infection, L. berlandieri tadpoles were susceptible. We believe that the active respiratory rhythm of the tadpoles when compared to the passive respiratory system of the salamander may account for this observation. Lastly, we examined host breadth and built a preliminary second intermediate host list for H. pumilio in Texas. Haplorchis pumilio has been known to occur in Texas for over a decade, and has been reported infecting snails in multiple spring-fed systems throughout the state. However, no second intermediate fish hosts have been reported hosting H. pumilio metacercariae in Texas, or the U.S.A. We examined the federally listed fountain darter (Etheostoma fonticola), Devils River minnow (Dionda diaboli), Pecos gambusia (Gambusia nobilis), Comanche Springs pupfish (Cyprinodon elegans); Texas protected Rio Grande darter (Etheostoma grahami) as well as the largemouth bass (Micropterus salmoides). With the exception of C. elegans, all species examined were positive for H. pumilio. We conclude that H. pumilio is likely present in many systems where their snail hosts have become established, and these finding present concern for human and wildlife health. 

Daniel Huston was born in Corpus Christi, TX. Daniel Received a B.S. in wildlife biology from Texas State University in 2011, and began an M.S. in biology in 2012. He has worked for the U.S. Fish and Wildlife Service throughout his graduate career, and enjoys topics pertaining to invertebrate biology.


Dissertation Defense

Wetlands, birds, and changing landscapes: examining avian communities
at multiple spatial extents

Suzanne Whitney

Major Advisor:
Dr. Joseph Veech

Committee Members:
Dr. Floyd Weckerly, Department of Biology
Dr. Weston Knowlin, Department of Biology
Dr. Erica Fleishman, University of California - Davis
Dr. Curt Flather, USDA – Forest Service, Fort Collins, CO

May 9, 2014 – 9:00 AM, SUPPLE 116

Destruction and impairment of wetlands has been extensive throughout the conterminous United States, resulting in the loss of both crucial ecosystem functions and productive habitat for a wide variety of organisms. Over the last few decades, efforts to protect, restore, and create wetlands have led to increases in wetland area and improvements to wetland quality in many locations. However, wetlands are difficult to create or restore, and whether these initiatives will lead to wetland function that approaches historical levels remains unclear. My research focuses on how the diverse bird communities that rely on wetlands might be affected by changes to their primary habitat and the surrounding landscape. I utilized data from the North American Breeding Bird Survey (BBS) and the National Land Cover Database (NLCD) to develop a set of spatially-explicit abundance models for each of 24 species of wetland-breeding birds. Independent variables in these models included combinations of three different aquatic habitats as well as other land cover types that could potentially influence species abundance. I compared the models in an information-theoretic framework to determine which cover types most influenced species abundance. All species were positively associated with one or more types of aquatic cover, and when considered in the broad spatial context of entire landscapes, other cover types likely affect abundances of many species as well. I also used data from the BBS and the NLCD to develop an inventory describing the characteristics of wetland bird communities and the composition of the landscape (including how these factors have changed over time) within several Bird Conservation Regions. The data included in this inventory indicate that wetlands and the bird communities associated with these systems have continued to experience substantial regional changes in recent years. Further, a review of previously published studies on avian use of anthropogenic wetlands suggests that while created and restored wetlands do support substantial bird communities, these assemblages are typically dissimilar from those at natural wetlands.

Suzanne graduated from California Lutheran University with a B.S. in Biology in 2004 and received her M.S. in Environmental Studies from the College of Charleston in 2008. She taught environmental education and worked on various ecological research projects in Oregon, California, Massachusetts, Puerto Rico, Mississippi, and South Carolina before moving to Texas. Suzanne entered the Aquatic Resources Ph.D. program at Texas State University in the fall of 2009 and has been supported as an Instructional Assistant for Organismal Biology and as a National Science Foundation GK-12 fellow with Project Flowing Waters.




Dissertation proposal Defense


Role of IBR5 in modulating SCF ubiquitin ligase mediated protein degradation in plant hormone response


Thilanka Jayaweera


Major Advisor:
Dr. Nihal Dharmasiri, Department of Biology, Texas State University.

Committee Members:
Dr. HongGu Kang, Department of Biology, Texas State University
Dr. Sunethra Dharmasiri, Department of Biology, Texas State University
Dr. Alan Lloyd, MCDB, University of Texas at Austin
Dr. William Gray, Department of Biology, University of Minnesota


May 9, 2014 – 2:00 pm Supple 153

The SCF (Skp1, Cullin, F-box) ubiquitin ligase dependent protein degradation is a common mechanism that regulates protein abundance of both plants and animals. This mechanism is involved in many cellular processes such as cell cycle, signaling cascades, and developmental processes. Several plant hormone signaling pathways such as auxin, gibberellic acid, ethylene, and jasmonic acid use the SCF dependent ubiquitin-proteasome pathway to regulate gene expression. In auxin signaling, auxin promotes the interaction between Aux/IAAs and SCFTIR1/AFBs and thereby enhances the ubiquitination and degradation of Aux/IAA repressors through 26S proteasome. The degradation of Aux/IAAs relieves the repression on ARFs leading to the modulation of gene transcription. Dual specificity phosphatase, IBR5 was identified as a protein involved in auxin signaling. Unlike in many other auxin insensitive mutants, Aux/IAA proteins are not stabilized, but rather degrade faster in ibr5-1 compared to the wild type suggesting that IBR5 negatively regulates Aux/IAA degradation. Also, the loss of ABP1 auxin receptor function leads to rapid Aux/IAA degradation similar to ibr5-1, suggesting that ABP1 and IBR5 function in a common signaling pathway to regulate SCFTIR1/AFBs dependent Aux/IAA degradation.

Overall goal of this study is to understand the molecular mechanism by which IBR5 regulates SCF ubiquitin ligase mediated protein degradation. Three ibr5 mutant alleles, ibr5-1, ibr5-4 and ibr5-5 as well as alternatively spliced IBR5.1 and IBR5.3 will be used to further understand the function of IBR5 in the above process. Also, experiments will be carried out to understand the interaction between ABP1 and IBR5, hypothesizing that IBR5 links ABP1 and TIR1/AFBs dependent auxin signaling pathways.

Thilanka Jayaweera was raised in Kandy, Sri Lanka and received his BS degree in Molecular Biology and Biotechnology from University of Peradeniya, Sri Lanka in May 2009. Then he entered the graduate College of Texas State University and earned his MS degree in Biology in fall, 2011. Thilanka entered the aquatic biology PhD program in spring 2012 to continue his research focused on auxin signaling in plants development. During his stay at Texas State he won several awards including Biology colloquium award, Colene Drace Cell Biology award, Graduate college scholarship and Dorothy Coker Research Fellowship.


Thesis Defense

Factors Affecting Phosphorus Uptake in Karstic Rivers of the Edwards Plateau, Central Texas

Aaron P. Swink
Major Advisor:   
Dr. Weston Nowlin
Committee Members:
Dr. Benjamin Schwartz, Department of Biology
Dr. Alan Groeger, Department of Biology
April 23, 2013 – 1:00 PM, FAB 130

Phosphorus (P) is a limiting nutrient for microbial primary producers in many aquatic systems and thus an overabundance of it via urban and agricultural runoff has led to eutrophication of waterways across the globe. There are a variety of ways to study nutrient dynamics, but nutrient spiraling theory is often used as a measure of efficiency and limitation in lotic ecosystems. However, the consistency, accuracy, and utility of the traditional metrics are questionable, especially as the discharge and hydrologic complexity of a stream or river increases. Thus, there is a relative dearth of knowledge on nutrient uptake in larger rivers, especially in spring-fed rivers. Recent improvements in methodology (i.e., pulsed tracer addition experiments) have allowed nutrient uptake length measurements to be performed in larger rivers in which it was cost-prohibitive to perform more traditional uptake methods (i.e., short-term steady state injection or isotope additions).
The purpose of this study was to quantify P uptake and examine the factors that influence P uptake in relatively larger discharge riverine ecosystems, specifically, in karstic, spring-fed rivers of the Edwards Plateau, in central Texas.

We utilized a pulsed tracer addition method to measure P uptake in 7 rivers and coupled these estimates with measurements of a diversity of in-stream and reach-level variables which are likely to exhibit influences on P uptake and retention in lotic ecosystems
We found that levels of chlorophyll-a and particulate P in benthic biofilms were significant predictors of uptake rates. In general, there was a high degree of covariance between benthic chlorophyll-a, benthic particulate P, water column SRP and dissolved mineral load indicating that biological and physicochemical factors are highly interrelated and work in concert to affect P cycling in these systems. Our results indicate that P uptake rates for the rivers in this study are rapid when compared to similarly sized non-karst rivers due to (1) the low availability of dissolved phosphate in the river, (2) abundance of algae-dominated biofilms, and (3) interaction with dissolved minerals (especially Ca2+), presumably resulting in precipitation of insoluble mineral forms of P. We have also shown that pulsed tracer additions can be a simple and effective tool for studying nutrient dynamics in streams and rivers.

Aaron Swink is from Kapaa, Hawaii. He attended Texas A&M University where he received a Bachelor of Science in Bioenvironmental Science in 2009. He has since worked for invasive species eradication projects in Hawaii and has done water quality monitoring for the San Marcos Observing System (SMOS) and the San Marcos Habitat Conservation Plan (SMHCP). In 2012, he was admitted to Texas State University to pursue a Master of Science in Aquatic resources. His primary areas of research interest are in freshwater biogeochemistry and karst hydrogeology and geomorphology.


Thesis Defense

Mating behavior and the effects of turbidity on association preferences in the fountain darter, Etheostoma fonticola.

Sophia L. DeColo


Major Advisor:
Dr. Caitlin R. Gabor

Committee Members:
Dr. Andrea Aspbury, Department of Biology
Dr. Kenneth Ostrand, USFWS

April 10, 2014 – 10:00 AM, Supple Norris Room

Anthropogenic activities such as industrial pollution, aquatic recreation, and increased groundwater withdrawal pose serious threats to aquatic ecosystems. Rising levels of turbidity as a result of these threats have serious consequences for aquatic organisms as turbidity degrades visual communication. The federally endangered fountain darter, Etheostoma fonticola, is endemic to the clear spring-fed headwaters of the San Marcos and Comal Rivers in central Texas. Here we tested the impact of simulated turbidity on association preferences in E. fonticola. We examined whether male and female E. fonticola exhibit preferences for larger over smaller individuals across two vision levels; clear and impaired (simulated low turbidity). We found that both female and male E. fonticola do not exhibit association preferences for larger over smaller individuals of the opposite sex or the same sex. Simulated low turbidity levels affected the total amount of time both female and male E. fonticola spent associating with individuals of the opposite sex. Reducing the amount of time spent associating with the opposite sex may reflect a reduction in the amount of time spent evaluating potential mates, thereby weakening sexual selection for traits important in mate choice. These results indicate that compromised vision hampers association preferences in E. fonticola, which may be of concern for the conservation and management of this endangered species.

Additionally we investigated the mating behavior of E. fonticola. Association preferences in E. fonticola did not reveal female or male mate preferences for size in this species. However, male-male interactions may influence mating behavior in E. fonticola and larger and smaller males may experience variation in mating success regardless of female preferences for size. Here we examined whether larger and smaller male E. fonticola exhibit differences in agonistic behavior and mating success. We found that larger males exhibited higher rates of aggressive behaviors and smaller males in turn exhibited more defensive behaviors. However, differences between larger and smaller males in male-male interactions were not correlated with differences in spawning success. These results suggest that male size influences dominance relationships in E. fonticola but not mating success. Combined with the results from our previous study, body size is not an important male trait for evaluating or choosing potential mates in female E. fonticola. As changing environmental conditions and anthropogenic activities threaten this endangered species, further understanding of the mating behavior of E. fonticola may be critical for their conservation and persistence.

Sophia DeColo was born in Boston, Massachusetts. She attended Northeastern University where she received a B.S. in Biology in 2010. While at Northeastern, she conducted undergraduate research in vertebrate paleontology and had the opportunity to work in the penguin colony at the New England Aquarium. Since then she has pursued various outlets to engage in animal husbandry and aid in conservation efforts. In 2012, Sophia entered Texas State University to pursue a Master of Science in Population and Conservation Biology.


Thesis Defense

Influence of a population irruption by Roosevelt elk on a vegetation index

Heath D. Starns


Major Advisor:
Dr. Floyd W. Weckerly

Committee Members:
Dr. M. Clay Green, Department of Biology
Dr. Thomas R. Simpson, Department of Biology


April 4, 2014 – 11:00 AM, SUPP 257

Understanding the factors that influence population growth is central to the study of any species. Large herbivores can influence their food supplies through herbivory. Over 23 years just before and throughout an irruption by a Roosevelt elk population I assessed temporal and spatial patterns of the Normalized Difference Vegetation Index (NDVI). My objectives were to determine if elk herbivory was associated with NDVI and whether the plant community foraged by the irruptive population was tolerant or resistant to elk grazing. Using Landsat 5 Thematic Mapper imagery, I obtained estimates of NDVI for three areas of Redwood National and State Parks, each inhabited by distinct populations of Roosevelt elk. Each population exhibited a different pattern of growth through the time series of the study. One population underwent the irruptive growth pattern while the other two populations did not. Using piece wise regression, I detected temporal changes in NDVI for the area used by the irruptive population that suggested a decline in forage biomass during the end of the dry season but I detected no decline in NDVI at the peak of the growing season. My findings suggest that the area used by the irruptive elk population may have undergone changes in plant community composition favoring plants that were resistant to elk grazing.

Heath received a B.S. in Wildlife Ecology and Management from Texas A&M University in August 2008. After graduating, he worked as assistant manager on a wildlife-focused ranch in south Texas for three years. Heath began his studies at Texas State in the Fall of 2012, and was recently awarded the Thesis Research Support Fellowship in Spring of 2014.


Thesis Defense


Ruben U. Tovar

Major Advisor:
Dr. Dana García

Committee Members:
Dr. Caitlin Gabor, Department of Biology, Texas State University
Dr. Glenn Longley, Department of Biology, Texas State University

April 2, 2014 – 10 am, Supple 153

The recent focus on conserved genes expressed through development has allowed for great headway in understanding the molecular mechanisms responsible for the variation seen among organisms. Understanding the expression of these integral developmental genes has implications with respect to evolutionary processes. The south central Texas Eurycea clade presents a unique continuum of karst phenotypes, having representative species of both subterranean and above ground morphotypes. By describing the adult ocular morphology and the developmental pathways leading to it, I hope to lay the foundation for better understanding the underlying molecular mechanisms responsible for subterranean phenotypes in a karst salamander system.
I am interested in exploring the evolution of developmental mechanisms that has resulted in the divergent ocular morphologies seen between the subterranean Texas blind salamander (Eurycea rathbuni) and the above ground Barton Springs salamander (Eurycea sosorum). To better understand the developmental processes of ocular reduction, a description of adult ocular histology was done first. The adult histology revealed an underdeveloped eye in the subterranean species E. rathbuni and well-developed eyes in the above ground species E. nana and E. sosorum. To understand how differences in gene expression influence the divergent outcomes of eye development between the two morphotypes, expression of genes involved in ocular development (pax6 and shh) was examined in E. rathbuni embryos and E. sosorum embryos. Pax6 and Shh are conserved across all animals and share similar expression patterns through development in species in which their expression has been examined. I found that both E. rathbuni and E. sosorum express Pax6 and Shh,butthe time course and location of Pax6 and Shh expression in the developing eye of the blind salamander differed from that in the sighted salamander. Furthermore, I observed unexpectedly that the lens, which functions in inducing development of the retina in other organisms, persists in the Texas blind salamander into the latest embryonic stages. I conclude that these salamanders present an ideal system in which to study the evolutionary and developmental mechanisms that lead to the variation in morphotypes seen in the Eurycea clade.

Ruben Tovar was born in San Antonio, Texas. He received a B.S. in Interdisciplinary Studies with a minor in Biology from the University of Texas, Arlington in 2010. His research interests lie broadly in herpetology, but his question of interest is in the subdiscipline of evolutionary developmental biology.


Dissertation Proposal

Predicting Future Range Expansion of Whooping Crane (Grus americana) Winter Habitat Using Long-Term Census and Remotely Sensed Data

Nicole A. Davis


Major Advisor:
Dr. Thomas Hardy, Department of Biology, Texas State University

Committee Members:
Dr. Clay Green, Department of Biology, Texas State University
Dr. Susan Schwinning, Department of Biology, Texas State University
Dr. Jennifer Jensen, Department of Geography, Texas State University
Dr. Elizabeth Smith, International Crane Foundation

April 1, 2014 – 3:30 pm Supple 112

Individual-based models (IBMs) have been utilized to explain various ecological processes. Examples include the influence of winter range carrying capacity on migrating bird survival, habitat choice in relation to range distribution, and changes in population dynamics from habitat degradation. The aim of my dissertation is to develop a spatially-explicit individual-based model to examine how behavioral patterns in wintering whooping cranes (Grus americana) influence territorial expansion and, most importantly, if these patterns may potentially limit territorial expansion below the seemingly available habitat. Whooping cranes have remained an endangered species since 1967, with only one wild-population remaining; the Aransas-Woods Buffalo population. Current conservation strategies regarding land protection for the Aransas-Woods Buffalo population within their wintering grounds along the Texas coast are limited by the uncertainty of future distribution as the population increases. I will develop winter range habitat suitability models for subadult and adult whooping cranes for inclusion in the individual-based model. The overall goal of the final IBM is to mimic past distributions of the Aransas-Woods Buffalo population within their wintering grounds along the Texas coast. The IBM could then be used as a conservation strategy tool to aid in future protection of the endangered Aransas-Woods Buffalo whooping crane population by producing predictions of winter distribution as the population increases.

Nicole received a B.S. in Biology from the University of Texas at San Antonio in December 2007 and a M.S. in Biology from Texas A&M University-Corpus Christi in May 2011. While attending Texas A&M-Corpus Christi, she was a NOAA Environmental Cooperative Science Center fellow and received the Teresa Heinz Scholar for Environmental Research Scholarship. Nicole joined the Aquatic Resources PhD program at Texas State University-San Marcos in the spring of 2012. She has remained an intern with the International Crane Foundation since joining Texas State and recently received a research grant from the Coypu Foundation.


Fall 2013

Dissertation Proposal Presentation

Influence of Brain-Derived Neurotrophic Factor and Family History of Alcohol Dependence on Alcohol Consumption Characteristics of Healthy Social Drinkers

Shobhit Sharma

Major Advisor:
Dr. Natalie Ceballos, Department of Psychology, Texas State University

Committee Members:
Dr. Brett Ginsburg, Department of Psychiatry, UTHSCSA
Dr. Dana Garcia, Department of Biology, Texas State University
Dr. Michelle Lane, Department of FCS, Texas State University
Dr. Shannon Weigum, Department of Biology, Texas State University

October 30, 2013 – 1:00 pm, LBJSC 3-11.1

Studies in animal models have suggested that decreased brain-derived neurotrophic factor (BDNF) levels may also be related to a genetic propensity for problem drinking. Studies in human participants have confirmed this relationship by examining presence vs. absence of the Val66Met single-nucleotide polymorphism (rs6265 SNP) of the BDNF gene, a genotype associated with decreased activity-dependent release of BDNF. Research suggests that BDNF may play a significant role in the reinforcing and rewarding effects of alcohol consumption and may be linked to genetic vulnerability to alcohol dependence. The proposed study will have following specific aims. Aim 1: will examine potential differences in salivary BDNF profiles among healthy social drinkers (aged 18-27) with and without a family history of alcohol dependence (FH), and the relationship of BDNF levels to alcohol use characteristics in these groups. Hypothesis 1: BDNF profiles are expected to be related to alcohol use characteristics such as quantity/frequency of alcohol consumption (the Val66Met polymorphism and lower BDNF associated with higher drinking levels), age of first drink and age of first drunken episode (lower BDNF associated with earlier initiation of alcohol use and drinking to excess), and binge drinking habits (lower BDNF associated with higher frequency and greater severity of binge drinking) compared negative controls (e.g., Val66Val). Aim 2: will examine the relationship between BDNF polymorphisms and 16-hour cortisol levels. Hypothesis 2: Previous studies have shown that carriers of the met-allele exhibit significantly attenuated HPA-axis activity. Similarly, individuals who are family history positive for alcohol dependence have also been shown to have attenuated HPA responses to stress. Preliminary data suggest a trend toward alcohol use differences between BDNF groups. The second step in the project, 16-hour cortisol levels, is currently underway in the existing genotyped participants. Based on this research, it is proposed that a synergistic effect of BDNF genotype and family history status may occur, such that family history positive participants with the BDNF Val66Met variant will show a differential effect on diurnal variation of cortisol levels as compared to all other groups.

Shobhit earned an MS in Biology from Texas State University in 2011 and entered the Ph.D. programin the Department of Biology at Texas State University in fall 2011. As a Ph.D. student, he has been employed as an instructional assistant for Anatomy and Physiology labs. In April 2013, Shobhit was awarded John P. McGovern Fellowship for his research from the Texas Research Society on Alcoholism in 2012. He also presented his research work at the Experimental Biology 2013 meeting.


Dissertation Defense


Benjamin T. Hutchins

Major Advisor:
Dr. Benjamin Schwartz

Committee Members: 
Dr. Timothy Bonner, Department of Biology, Texas State University-San Marcos
Dr. Weston Nowlin, Department of Biology, Texas State University-San Marcos
Dr. Annette Engel, Department of Earth & Planetary Sciences, University of Tennessee-Knoxville
Dr. Stephen MacAvoy, Department of Biology, American University

Nov. 1, 2013 – 1:00 PM, Supple 116

Food web complexity is closely tied to nutrient availability which is often assumed to be severely limiting in subterranean ecosystems. However, this is assumption is largely based on studies in relatively shallow habitats dependent on allochthonous, photosynthetic detritus. The Edwards Aquifer of Central Texas provides an interesting opportunity to examine food web structure in a deep, phreatic setting because 1) it has an unusually diverse faunal assemblage and 2) both allochthonous detritus and autochthonous, chemolithoautotrophic organic matter are supplied to the aquifer in spatially isolated regions. Both of these nutrient sources are spatially and temporally variable within the aquifer, and both are consumed by metazoan taxa. However, the relative contribution of allochthonous and autochonous organic matter to consumers varies within the aquifer as a function of hydrologic proximity to organic matter sources. The presence of two disparate food resources promotes niche partitioning among sympatric species, and this trophic specialization is reflected in morphologic adaptations. Horizontal trophic diversity (primary consumers feeding on multiple resources) increases biomass available to higher level consumers, resulting in a food web longer than any previously reported from a groundwater habitat. A meta-analysis of groundwater foodweb studies suggests that ecosystem age, ecosystem size, and predator-prey mass ratios also affect trophic length in groundwater foodwebs. These data suggest that the prevailing paradigm of food web structure in subterranean ecosystems is overly simplistic.

Benjamin Hutchins was born in Louisville, KY and received a B.S. in Biology from Western Kentucky University in 2005. He then attended American University in Washington DC, earning a M.S. in Biology in 2007. Ben has acted as a biological consultant on several projects, and he and his wife Carrie served 2 years as Peace Corp volunteers in Morocco prior to his entry into the Aquatic Resources Ph.D. program in the fall of 2009.


Thesis Defense

Prevalence of Batrachochytrium dendrobatidis in amphibian communities of Central Texas and Tamaulipas, Mexico

Andrea Villamizar Gomez


Major Advisor:
Dr. Michael Forstner

Committee Members:
Dr. Dittmar Hahn, Dept. Biology
Dr. Ivan Castro Arellano, Dept. Biology

November 05, 2013 – 8:00 am Norris Room, Supple 376-A.

Batrachochytrium dendrobatidis (Bd), a fungus that causes chytridiomycosis on infected amphibians, and has been implicated as a potential causative agent in the amphibian population declines of the past 50 years. This study seeks to assess the prevalence of Bd in amphibian communities in Central Texas and the state of Tamaulipas, Mexico. In Central Texas two counties were evaluated during the spring of 2012, and for the Tamaulipas assessment samples of 18 amphibian species were collected between 2004 and 2008 at 16 different localities that ranged from 100-2900 meters in elevation. All the samples were obtained from non-consumptive toe clippings and swabs. The presence of the pathogen was assessed by using a Taqman quantitative real time PCR (qPCR) assay in a highly sensitive approach to detection. Interestingly, there is a low prevalence for Bd in Central Texas in comparison with previous studies conducted in this area. All samples tested from Tamaulipas were negative for the presence of the pathogen. This study implies that monitoring the pathogen in both southern Texas and northern Mexico requires explicit changes to normal surveys protocols. To better understand the dynamics of the fungus in these environments, will require increased efforts during periods that accommodate pathogen thermal preferences. Further exploration in this regions and adjacent areas will help to inform of the prevalence, widespread and epidemiology of Bd and would help prioritize conservation efforts.

Andrea Villamizar Gomez, was born in Bogota, Colombia. She completed the degree of Bachelor in Veterinary Medicine at UDCA University in Bogota. After graduating with a Bachelor’s degree in 2008, she practiced for 3 years before starting her Master’s program in Wildlife Ecology at Texas State University-San Marcos under the supervision of Dr. Michael Forstner during August 2011.