Thesis Title: An Assessment of Assortative Mating and Sexual Size Dimorphism in Two Tiger Beetle Species

Research Advisor: Major Advisor (Thesis Chair): Chris Nice
Committee Members James Ott and Caitlin Gabor

ABSTRACT
Size assortative mating and female-biased sexual size dimorphism (SSD) are expected to occur in taxa with post-copulatory mate guarding due to selection for male choice of large females when male time investment is high. Facultative mating behaviors are also predicted to occur in these taxa when changes in the social environment alter the benefits for guarding males. I used field observations and lab experiments in 2006 and 2007 to investigate the factors influencing mating behaviors in two tiger beetle species that exhibit mate guarding behavior in central Texas, Cicindela belfragei and C. formosa. Both species displayed female-biased SSD, but size assortative mating did not occur in the field. Large mates were not preferred by either sex, but mate guarding and copulation durations were affected by female size, indicating that males may be capable of assessing female size once paired with a female. The social environment of C. belfragei in experiments did not affect guarding, copulation, or total amplexus durations, but in C. formosa, social context was important. The results of this study suggest that male choice of large females does not cause the female-biased SSD in these species, assortative mating may not be a characteristic of these species, and that mating behavior durations may not be affected by the extent of mating male harassment by non-mating males or by the outcome of male contests for females. Instead, this study supports previous findings, that Cicindela mating behavior may be determined by other factors, such as the location of oviposition sites and the ability to fly.

Thesis Title: Pollinator Effectiveness, Pollinator Importance, and Pollen Dispersal in Star Cactus

Research Advisor: Major Advisor (Thesis Chair): Paula Williamson
Committee Members James Ott and Chris Nice

ABSTRACT

Thesis Title: Population Genetics and Conservation of Texas Hill Country Salamanders (Eurycea)

Research Advisor: Major Advisor (Thesis Chair): Chris Nice
Committee Members: Caitlin Gabor, James Ott and Joe Fries

ABSTRACT
The Texas Hill Country is composed of isolated aquatic habitats that are inhabited by a variety of endemic aquatic organisms, many of which have restricted ranges and are threatened by human usage of aquatic resources. Among this fauna are the spring-adapted, neotenic salamanders of the genus Eurycea. I examined mitochondrial and nuclear sequence variation of seven Eurycea populations to address the following questions: 1) to what extent does gene flow occur among these populations?, 2) do river systems and/or aquifers serve as conduits for gene flow in this system?, and 3) what is the status of the populations, measured by population size and growth rate? The number of pairwise migrants per generation based on non-equilibrium pairwise migration rates was less than one for all pairs of populations except JacobÂ's Well and DevilÂ's Backbone. There was a significant correlation between non-equilibrium migration rate and geographic distance. Partial mantel tests revealed that what little gene flow occurs among population does not appear to be facilitated by current aquifer or river systems. Each of the populations sampled in this study likely constitutes a unique entity and should be managed as such. Population size estimates are reasonably large (approximately 178,100-1,720,600) and are coupled with no evidence of population decline. The Comal Springs population has the largest estimated population size, and appears to be growing.  I also examined genetic variation and structure within the San Marcos Springs Eurycea population (E. nana) and between this wild population and the refuge population housed at the San Marcos National Fish Hatchery and Technology Center. There is no significant genetic structure among three sites sampled within the wild population. Estimates of genetic diversity for the wild and refuge populations are not significantly different.

Zachariah Gompert

Thesis Title: Evolutionary Consequences of Hybridization in the Lycaeides Species Complex

Research Advisor: Major Advisor (Thesis Chair): Chris Nice
Committee Members: Dr. Jim Ott, Dr. Mike Forstner, Dr. Gary Upchurch, and Dr. Dan Bolnick

ABSTRACT
I examined the consequences of hybridization at two contact zones between previously isolated Lycaeides (Lepidoptera: Lycaenidae) populations. First I investigated a contact zone between the North American endangered Karner Blue Butterfly (L. melissa samuelis) and the closely related L. m. melissa. Western populations of L. m. samuelis share mitochondrial haplotypes with L. m. melissa populations, while eastern populations of L. m. samuelis have divergent haplotypes. I tested two hypotheses concerning the presence of L. m. melissa mitochondrial haplotypes in western L. m. samuelis populations: 1) mitochondrial introgression has occurred from L. m. melissa populations into western L. m. samuelis populations, or 2) western populations of the L. m. samuelis are more closely related to L. m. melissa than to eastern L. m. samuelis populations yet are phenotypically similar to the latter. Multilocus genetic data clearly differentiated L. m. samuelis and L. m. melissa. These findings support the hypothesis that the presence of L. m. melissa mitochondrial haplotypes in western L. m. samuelis populations is the result of mitochondrial introgression, and illustrate the risks of using data from a single locus for diagnosing significant units of biodiversity for conservation. Second, I tested the hypothesis that alpine adapted Lycaeides populations at a contact zone in the Sierra Nevada arose via hybrid speciation between L. idas and L. melissa. Using molecular data and data from ecological experiments, I demonstrated that the alpine-adapted butterflies in the genus Lycaeides are the product of hybrid speciation. I showed that the alpine populations possess a mosaic genome derived from both L. melissa and L. idas and that these populations are differentiated from, and younger than, their putative parental species. Adaptive traits that allow persistence of these populations in the environmentally extreme alpine habitat also reproductively isolate these populations from their parental species, as predicted by theory.