Inferences of evolutionary relationships in most groups of organisms have traditionally been based on morphological characters. In recent years, however, the use of molecular data has become widespread in systematics. Although there is usually close agreement between morphology-based and molecule-based inferences about phylogeny, there are special cases in which rates of evolution in the two components differ greatly. This appears to hold for salamanders of the tribe Hemidactyliini in the family Plethodontidae, in which morphological characters alone do not appear to provide a reliable estimate of phylogeny. Knowledge of patterns of genetic divergence in this group (which may occur in the absence of morphological differentiation) also has implications for the conservation of these salamanders and their habitat, especially because some of the species involved are threatened by habitat destruction. Under the guidance of faculty advisor David Hillis, graduate student Paul Chippindale will use several molecular systematic techniques to reconstruct phylogenetic relationships among these salamander species. The techniques include protein electrophoresis, restriction enzyme analysis of nuclear ribosomal and mitochondrial DNA, and sequencing of mitochondrial genes. Special emphasis is placed on the surface and cave-dwelling central Texas salamanders of the genera Eurycea and Typhlomolge, with a diversity of morphologies and of life histories.The research will determine whether parallel changes in morphology and in life history characterize this group, and it will also test hypotheses about the evolutionary significance of changes in genome size.
