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.
