I am a Ph.D. candidate in the Department of Zoology at Oregon State University. I am an evolutionary biologist interested in a variety of topics. The fundamental questions that I ask are in regards to the nature of phenotypic evolution. Why do some populations adapt and spread while others do not? Why do we observe rapid evolution in field studies, but the fossil record and living diversity suggest that evolution is slow? What factors contribute to the evolution of phenotypic diversity? How do population level models of phenotypic evolution scale up to evolution across a species range over evolutionary time?
Gene flow and the diversification of the western Garter Snakes (Thamnophis). Much of my research focuses on the evolution of the Western Terrestrial garter snake, Thamnophis elegans. This is a polytypic species with a wide geographic range throughout the west. Preliminary phylogenetic data using mitochondrial sequences suggest a complex pattern of divergence that is not concordant with current subspecies designations. There is considerable variation in this group, much of it reflecting differences in geographic variation in diet (T. elegans has among the broadest diets of any snake) and habitat. These snakes are found from the desert floor to over 10,000 feet in the Sierra mountains. They range ecologically from slug-eating specialists to piscivory, and everything in between. My research examines the importance of gene flow between differentially adapted forms in generating diversity in the western garter snake clade. I am examining this across the entire radiation, which shows evidence of ancient hybridization and gene flow in several species. In addition, I am examining whether hybridization in contemporary populations increases or decreases the potential for local adaptation and range expansion. I will address this question by examining the G-matrix of several hybrid populations between subspecies of T. elegans to determine if the genetic architecture necessary for adaptation is present in natural hybrid zones. Evolutionary quantitative genetics and the G-matrix provides a framework for assessing evolvability of populations, and may influence patterns of diversification across the genus as a whole.
The Paradox of Stasis- working toward biologically informed process models. Biologists often study evolution across very different timescales. Selection studies study phenotypic change over the course of a few years, while paleontologists study divergence over millions of years. It has long been noted that evolutionary rates can be quite rapid over just a few generations, but that these changes do not scale up over evolutionary time, where paradoxically slow rates of change prevail. Why does so little phenotypic change accumulate when the potential for change is so great? Can phenotypic models of evolution based on evolutionary genetics and the adaptive landscape explain patterns of divergence across all timescales? I am currently collaborating with researchers at the University of Oslo to characterize patterns of divergence across different timescales and to develop models that provide a clear connection to adaptation and genetics. Such models are particularly important to our interpretation of evolutionary patterns of divergence, particularly in the case of widely used comparative methods.
Sexual selection and drift. Together with my collaborators, I have published a paper in Evolution that examines the potential for genetic drift coupled with sexual selection to drive speciation by reproductive isolation. This paper is a first step towards making a connection between quantitative genetic models of sexual selection and and empirical patterns of reproductive isolation. Furthermore, we are particularly interested in the potential for drift to enhance divergence and isolation among populations. Consequently, we are pursuing analyzing models of sexual selection with stochastic differential equations, as stochastic equilibria may produce dramatically different evolutionary outcomes when compared with their deterministic counterparts.
Gulf of Guinea Herpetofauna . Working with Dr. Bob Drewes at the California Academy of Sciences, I have described a new species of frog from the genus Phrynobatrachus from the Gulf of Guinea islands in Africa (PDF). The presence of any amphibians on these oceanic islands is a perplexing biogeographic mystery, as all of 7 species found there are endemic and must have dispersed to the islands over salt water, a feat typically thought to be near impossible for amphibians. I have had the opportunity to accompany two expeditions organized by Dr. Drewes to these wonderful islands.