Speciation and Phylogenetic Diversification in a Polytypic Amphibian

谢弗博士将研究种类繁多、变异极大的北美虎火蜥蜴的物种形成和分化的过程以及模式。该项目有两个基本目标。首先，它使用了一系列来自分子生物学的新技术，从北美和墨西哥的火蜥蜴种群中收集DNA序列数据。序列数据将被用来确定火蜥蜴的系统发育关系，使用DNA的相似和差异模式作为共同祖先最近的指示。这些结果将补充谢弗博士之前进行的关于老虎火蜥蜴系统发育关系的研究，并将回答关于这种大陆分布的物种如何发生遗传多样性的基本问题。谢弗博士还将研究这种遗传分化的进化机制。为此，将进行繁殖实验，量化田间缺乏杂交的程度，原因是1)交配后发生的发育异常，或2)种群之间的行为差异，使它们不太可能相互求爱和交配。通过将这种机制方法与分化进化模式的分子描述相结合，这项研究将提供一种独特的、深入的分析，说明物种形成是如何在广泛的脊椎动物物种中发生的。

Dr. Shaffer will examine the process, as well as the pattern, of speciation and differentiation in the wide-ranging, extremely variable North American Tiger salamanders. The project has two fundamental objectives. First, it uses a new series of techniques from molecular biology to collect DNA sequence data from salamander populations from across North America and Mexico. The sequence data will be used to determine the phylogenetic relationships of the salamanders, using patterns of similarity and differences in DNA as an indicator of recency of common ancestry. These results will complement previous research conducted by Dr. Shaffer on the phylogenetic relationships of tiger salamanders and will answer fundamental questions on how genetic diversification has occurred in this continentally distributed species. Dr. Shaffer will also examine the mechanisms by which this genetic differentiation has evolved. To do so, breeding experiments will be conducted that quantify the extent to which a lack of interbreeding in the field is attributable to either 1) developmental abnormalities that occur after mating, or 2) behavioral differences between populations that make them less likely to court and mate with one another. By interfacing this mechanistic approach with the molecular description of the evolutionary pattern of differentiation, the research will provide a unique, in-depth analysis of how speciation occurs in wide-ranging vertebrate species.