Graduate

A major goal of evolutionary biology and ecology is to understand why species richness varies among clades. Previous studies have suggested that variation in richness among clades might be related to variation in rates of morphological evolution among clades (e.g., body size and shape). Other studies have suggested that richness patterns might be related to variation in rates of climatic-niche evolution. However, few studies, if any, have tested the relative importance of these variables in explaining patterns of richness among clades. Here, we test their relative importance among major clades of Plethodontidae, the most species-rich family of salamanders. Earlier studies have suggested that climatic-niche evolution explains patterns of diversification among plethodontid clades, whereas rates of morphological evolution do not. A subsequent study stated that rates of morphological evolution instead explained patterns of species richness among plethodontid clades (along with "ecological limits" on richness of clades, leading to saturation of clades with species, given limited resources). However, they did not consider climatic-niche evolution. Using phylogenetic multiple regression, we show that rates of climatic-niche evolution explain most variation in richness among plethodontid clades, whereas rates of morphological evolution do not. We find little evidence that ecological limits explain patterns of richness among plethodontid clades. We also test whether rates of morphological and climatic-niche evolution are correlated, and find that they are not. Overall, our results help explain richness patterns in a major amphibian group and provide possibly the first test of the relative importance of climatic niches and morphological evolution in explaining diversity patterns.

The genus Aneides (Caudata: Plethodontidae) is an arboreal salamander with a prehensile tail and a distribution that spans North America. It is hypothesized that adaptations for arboreality will be visible in the osteology of the sacral vertebra either by qualitative analysis or linear and morphometric analysis in comparison with other plethodontid salamanders. This study demonstrates that while qualitative and quantitative analyses are successful at making genus-level distinctions between taxa, identification to lower taxonomic levels remains inconclusive. Linear morphometrics and dorsal Procrustes landmarks were the most successful metrics to identify known taxa. Two unidentified fossil salamander sacral vertebrae from Oregon Caves National Monument are examined with the same techniques and are tentatively identified as Hydromantes based on qualitative similarities to modern Hydromantes specimens, as the quantitative analyses were unable to confidently diagnose the unknown specimens.

The salamander diversity in the southern Appalachian Mountains is now being threatened, with lungless salamanders (family Plethodontidae) likely the most vulnerable. Multiple environmental factors threaten Plethodontids, and environmental changes uniquely affect each species within this family. Unfortunately, there is a lack of understanding about the current status of salamanders in Greene County, TN that severely limits conservation efforts for lungless salamanders. This study examined local salamander populations’ current distributions and connected salamander abundance and species richness with a subset of environmental factors to determine what areas represent suitable habitat for different Plethodontids. This information was used to develop species distribution models, which were used to identify potential areas of salamander habitat to focus management and conservation efforts. Area constrained surveys were completed at 42 transects within four main areas using a robust, random sampling design. Abiotic and biotic data, along with salamander identification, were documented at each site. Four additional variables were acquired by geographic information system (GIS 10.6). Salamanders were present at 69% of the transects. Our results indicate that salamanders tend to be located at higher elevations, in ravines, and in thicker canopy cover areas. This work will be useful in long-term monitoring and future research as salamander population, habitat, and environmental changes continue to be monitored.

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