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Noland Martin, Ph.D.

Department of Biology 


noland martin 

Noland H. Martin, Ph.D.

Assistant Professor

Phone: 512-245-3317
Fax: 512-245-8713
Office: SUPP 160

Department of Biology
Texas State University - San Marcos
601 University Drive
San Marcos, TX 78666

Courses Taught

  • Evolution - Bio 4301
  • Genetics - Bio 2450

Research Interest

 The primary focus in the lab centers around the ecological genetics of speciation and natural hybridization. How are populations transformed into new species? What are the evolutionary consequences of natural hybridization? These are two of the most fundamental and interrelated questions in evolutionary biology, and with new ecological, molecular and statistical genomic techniques, answering them is a distinct possibility. The evolution of new species is generally thought to be a consequence of genetic divergence between populations ultimately resulting in complete reproductive isolation. However, reproductive isolation is often incomplete and hybridization may occur between genetically divergent taxa. While the mere existence of hybrids often fuels debate as to the usefulness of long- standing species concepts, naturally hybridizing taxa provide unique opportunities to study speciation "as it happens" before the process has been completed. To understand hybridization and speciation in both a genetic and ecological context, I use large-scale field studies, greenhouse experiments, and genomic-scale analyses in Louisiana Iris. Evolutionary biology requires the integration of such diverse types of data, and my research program illustrates the potential for using these data to ask a broad range of questions about the origin of species and the long-term consequences of natural hybridization.

The primary study system that we work on is Louisiana Iris. The Louisiana Iris species complex consists of three geographically widespread species: Iris brevicaulis, Iris, fulva, and Iris hexagona. All species are found sympatrically in southern Louisiana where natural hybrid zones can frequently be encountered. We are interested in the consequences of such natural hybridization, which can include adaptive introgression and even hybrid speciation. We have utilized QTL mapping to examine the genetic architecture of reproductive isolating barriers between Louisiana Iris species, which has also resulted in the identification of genomic regions responsible for adaptive introgression. We are now using high-throughput “next-generation” sequencing technologies to not only produce high-density genetic linkage maps for QTL mapping, but also to quantify introgression patterns and perform admixture mapping in natural hybrid zones.

A fourth Louisiana Iris species, Iris nelsonii has a very small geographic distribution and occurs only in a single Parish in Southern Louisiana. This unique species, however, has been documented to be of homoploid hybrid origin – a product of hybridization between all three of the more widespread Louisiana Iris species. Molecular evidence reveals that a large portion of the I. nelsonii genome is derived from I. fulva with a minority of the genome consisting of small introgressed regions that originated from I. hexagona and I. brevicaulis. When experimental crosses are made between I. nelsonii and its progenitors, the resulting hybrids are viable and quite fertile, suggesting that intrinsic postzygotic isolation contributes little to the total isolation observed between these species. Instead, it is likely that ecological isolation played a primary role in the origin (and current maintenance) of I. nelsonii. Another primary research focus in the lab thus focuses on integrating genomic and experimental approaches to examine ecological isolation in this species. Furthermore, because Iris nelsonii is rare and geographically restricted, the Louisiana Department of Wildlife and Fisheries (LDWF) have identified it as a “species of concern”. As such, we have an ongoing collaboration with LDWF whereby our work on the ecological requirements of I. nelsonii directly informs conservation planning for this unique species.

I am currently seeking enthusiastic Masters and PhD students to join my lab.


Ph.D. 2004 Biology Duke University
M.S. 2000 Biology University of Oregon
B.S. 1996 Biology University of Texas at Austin



1. NH Martin. 2004. Flower size preferences of the honeybee (Apis mellifera) foraging on Mimulus guttatus (Scrophulariaceae). Evolutionary Ecology Research 6: 777-782. [PDF]
2. NH Martin, AC Bouck, ML Arnold. 2005. Loci affecting long-term hybrid survivorship in Louisiana Irises: Implications for reproductive isolation and introgression. Evolution 59 (10), 2116-2124.  [PDF]
3. NH Martin, AC Bouck, ML Arnold. 2006. Detecting adaptive trait introgression between Iris fulva and I. brevicaulis in highly selective field conditions. Genetics 172 (4), 2481-2489. [PDF]
4. NH Martin, JH Willis. 2007. Ecological divergence associated with mating system causes nearly complete reproductive isolation between sympatric Mimulus species. Evolution 61 (1), 68-82. [PDF]
5. NH Martin, AC Bouck, ML Arnold. 2007. The genetic architecture of reproductive isolation in Louisiana irises: flowering phenology. Genetics 175 (4), 1803-1812 [PDF]
6. NH Martin, Y Sapir, ML Arnold. 2008. The genetic architecture of reproductive isolation in Louisiana irises: pollination syndromes and pollinator preferences. Evolution 62 (4), 740-752. [PDF]
7. ML Arnold, Y Sapir, NH Martin. 2008a. Genetic exchange and the origin of adaptations: prokaryotes to primates. Philosophical Transactions of the Royal Society B: Biological Sciences 363 (1505), 2813-2820. [PDF]
8. ML Arnold, RS Cornman, NH Martin. 2008b. Hybridization, hybrid fitness and the evolution of adaptations. Plant Biosystems 142 (1), 166-171. [PDF]
9. PJ Devries, GT Austin, NH Martin. 2008. Diel activity and reproductive isolation in a diverse assemblage of Neotropical skippers (Lepidoptera: Hesperiidae). Biological Journal of the Linnean Society 94 (4), 723-736. [PDF]
10. AL Sweigart, NH Martin, JH Willis. 2008. Patterns of nucleotide variation and reproductive isolation between a Mimulus allotetraploid and its progenitor species. Molecular Ecology 17 (8), 2089-2100. [PDF]
11. SJ Taylor, M Arnold, NH Martin. 2009. The genetic architecture of reproductive isolation in Louisiana irises: hybrid fitness in nature. Evolution 63 (10), 2581-2594 [PDF]
12. ML Arnold, NH Martin. 2009. Adaptation by introgression. Journal of Biology 8 (9), 82. [PDF]
13. PJ Devries, GT Austin, NH Martin. Estimating species diversity in a guild of Neotropical skippers (Lepidoptera: Hesperiidae) with artificial lures is a sampling problem. 2009. Insect Conservation and Diversity 2 (2), 125-134. [PDF]
14. NH Martin, JH Willis. 2010. Geographical variation in postzygotic isolation and its genetic basis within and between two Mimulus species. Philosophical Transactions of the Royal Society B: Biological Sciences 365 (1552), 2469-2478. [PDF]
15. ML Arnold, S Tang, SJ Knapp, NH Martin. 2010. Asymmetric introgressive hybridization among Louisiana Iris species. Genes 1 (1), 9-22. [PDF]
16. ML Arnold, NH Martin. 2010. Hybrid fitness across time and habitats. Trends in Ecology & Evolution 25 (9), 530-536. [PDF]
17. S Tang, RA Okashah, SJ Knapp, ML Arnold, NH Martin. 2010. Transmission ratio distortion results in asymmetric introgression in Louisiana Iris. BMC Plant Biology 10 (1), 48. [PDF]
18. SJ Taylor, RW Willard, JP Shaw, MC Dobson, NH Martin. 2011. Differential response of the homoploid hybrid species Iris nelsonii (Iridaceae) and its progenitors to abiotic habitat conditions. American Journal of Botany 98 (8), 1309-1316. [PDF]
19. MC Dobson, SJ Taylor, ML Arnold, NH Martin. 2011. Patterns of herbivory and fungal infection in experimental Louisiana Iris hybrids. Evolutionary Ecology Research 13 (5), 543-552. [PDF]
20. BG Benedict, JL Modliszewski, AL Sweigart, NH Martin, FR Ganders, JH Willis. 2012. Mimulus sookensis (Phrymaceae), a new allotetraploid species derived from Mimulus guttatus and Mimulus nasutus. Madroño 59 (1), 29-43. [PDF]
21. E Ballerini, A Brothers, S Tang, S Knapp, A Bouck, S Taylor, M Arnold, N Martin. 2012. QTL mapping reveals the genetic architecture of loci affecting pre-and post-zygotic isolating barriers in Louisiana Iris. BMC Plant Biology 12 (1), 91. [PDF]

22. SJ Taylor, KJ AuBuchon, NH Martin. 2012. Identification of Floral Visitors of Iris nelsonii. Southeastern Naturalist 11 (1), 141-144. [PDF]

23. SJ Taylor, LD Rojas, SW Ho, NH Martin. 2013. Genomic collinearity and the genetic architecture of floral differences between the homoploid hybrid species Iris nelsonii and one of its progenitors, Iris hexagona. Heredity 110, 63-70. [PDF]