Doctoral Dissertation Research: Testing for Ecological Speciation with Phylogeographic Data

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The various processes involved in the formation of species are not well understood. One of the leading hypotheses, ecological speciation, proposes that populations of the same species living in different regions will diverge over time in response to differing environments. Eventually these changes will accumulate, resulting in the formation of different species. This research will test the hypothesis of ecological speciation by studying multiple species of snakes in the Sonoran and Chihuahuan deserts where it has been shown that closely populations in the two regions have divergent DNA sequences. Using a combination of genomic DNA sequence data, anatomy, morphology, and climate data, researchers will test whether predictions from ecological speciation account for differences observed between these recently diverged populations. This research will train one graduate student and provide undergraduate students with early training in molecular evolutionary studies and diverse laboratory techniques. Data collected from the research will be used to design a new course for graduate students, who can then apply similar methods to address their own research questions in systematics and evolutionary biology.The ecological speciation hypothesis states that reproductive isolation is a byproduct of natural selection on divergent ecologies between species. Alternatively there are several non-ecological mechanisms by which speciation can occur, including genetic drift, the fixation of incompatible mutations, or sexual selection. Under the hypothesis of ecological speciation it is expected that reproductive isolation will be correlated with ecological differentiation. The proposed study will test for the signature of ecological speciation in a group of snakes that share a common phylogeographic break between the Sonoran and Chihuahuan deserts. Researchers will collect high-throughput genomic DNA sequence data and measure reproductive isolation between pairs of sister taxa. Ecological niche models and morphometrics will be used to measure ecological divergence between populations. Bayesian model averaging will then be used to assess the affects of ecological divergence and time on reproductive isolation. This research will address whether ecological divergence is driving speciation at recent time scales, and test its importance in generating species level diversity. Further, the study will help to illuminate the mechanisms responsible for generating high regional species diversity in this biodiversity hotspot.