Doctoral Dissertation Research: Testing for Ecological Speciation with Phylogeographic Data

物种形成的各种过程还没有被很好地理解。其中一个主要的假说是生态物种形成，它提出生活在不同地区的同一物种种群会随着时间的推移而因不同的环境而分化。最终，这些变化会累积起来，形成不同的物种。这项研究将通过研究索诺兰沙漠和奇瓦瓦沙漠的多种蛇来检验生态物种形成的假设，这两个地区的近距离种群具有不同的DNA序列。利用基因组DNA序列数据、解剖学、形态学和气候数据的组合，研究人员将测试生态物种形成的预测是否能解释这些最近分化的种群之间观察到的差异。本研究将培养一名研究生，并为本科生提供分子进化研究和多样化实验室技术的早期训练。从研究中收集的数据将用于为研究生设计一门新的课程，然后他们可以应用类似的方法来解决他们自己在系统学和进化生物学方面的研究问题。生态物种形成假说认为，生殖隔离是物种间不同生态的自然选择的副产品。另外，还有一些非生态机制可以导致物种形成，包括遗传漂变、不相容突变的固定或性选择。在生态物种形成假说下，生殖隔离与生态分化有一定的联系。这项拟议的研究将测试一群蛇的生态物种形成特征，这些蛇在索诺兰沙漠和奇瓦瓦沙漠之间共享一个共同的系统地理断裂。研究人员将收集高通量基因组DNA序列数据，并测量姐妹类群对之间的生殖隔离。生态位模型和形态计量学将用于测量种群间的生态差异。然后使用贝叶斯模型平均来评估生态分化和时间对生殖隔离的影响。本研究将探讨生态分化是否在最近的时间尺度上推动物种形成，并测试其在产生物种水平多样性方面的重要性。此外，该研究将有助于阐明这一生物多样性热点地区产生高区域物种多样性的机制。

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.