Speciation and Phylogenetic Diversification in a Polytypic Amphibian

谢弗博士将研究分布广泛、变化多端的北美虎蝾螈的物种形成和分化过程以及模式。该项目有两个基本目标。首先，它使用分子生物学的一系列新技术来收集来自北美和墨西哥的蝾螈种群的DNA序列数据。序列数据将用于确定蝾螈的系统发育关系，使用DNA的相似性和差异模式作为共同祖先近代性的指标。这些结果将补充Shaffer博士之前对虎蝾螈系统发育关系的研究，并将回答有关这种分布在大陆上的物种如何发生遗传多样化的基本问题。谢弗博士还将研究这种基因分化进化的机制。为此，将进行育种实验，量化野外杂交缺乏的程度：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，该研究将为广泛的脊椎动物物种如何形成提供独特而深入的分析。

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.