Collaborative Research: Phylogeny and Montane Species Richness in Plethodontid Salamanders

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The investigators will reconstruct the phylogeny of plethodontid salamanders using morphological and molecular data and then use the phylogeny to explore how species diversity changes with elevation, and the evolutionary reasons for patterns of species richness. Plethodontidae is the largest family of salamanders, containing about two-thirds of all 460+ species of salamanders. Plethodontids are possibly the most abundant vertebrates in eastern North America and are the focus of research by dozens of scientists in many diverse fields of biology (e.g., ecology, behavior, morphology, evolution, development). Many (if not most) of these studies depend critically on having a robust phylogenetic framework. However, higher-level relationships among plethodontids have never been the subject of a comprehensive study using modern methods. In a three-year collaborative study, the PIs will reconstruct the phylogeny of 112 species of plethodontid salamanders (plus outgroups representing five other families) using morphological characters and DNA sequences from two mitochondrial genes and one nuclear gene. The phylogeny will be used to explore how and why species diversity changes with elevation, using the unusually rich salamander fauna of the Appalachian Mountains as a model system. Many groups of organisms exhibit increased species diversity in montane areas relative to lowland areas, a widespread pattern that remains poorly explained. It is suggested herein that this pattern results from increased speciation in montane regions caused by the disjunctive nature of montane habitats and the elevational habitat specificity of highland species. Three key predictions of this model will be tested using phylogenetic methods. The study will provide the first phylogeny of plethodontid salamanders based on a rigorous analysis of morphological and molecular data. The phylogeny will be critical to dozens of researchers who use plethodontids as a model system in studies of ecology, behavior, evolution, development, and other areas of biology. The study will also be the first to address elevational patterns of species richness from a phylogenetic perspective. These analyses of montane species richness should have important implications for the fields of ecology, evolution, biogeography, and conservation biology. For example, the analyses of elevational specificity (how narrowly adapted a species is to a given elevational range and its associated climate) may be important for predicting the persistence or extinction of montane species in relation to global warming or other changes in climate. The study will provide training for undergraduate and graduate students and a postdoctoral fellow in molecular techniques and in integrated analyses of phylogeny, ecology, and evolution.