Differentiation across multiple spatial scales in three Californian amphibians

Current distributions of species, connectivity of populations, and physiological adaptations have arisen through a dynamic past, and our interpretations of the patterns and the processes involved is heavily dependent on the scale at which we conduct our studies. To understand broad patterns of amphibian diversification, I conducted phylogeographic analyses of the widely distributed mountain yellow-legged frog (Rana muscosa) and confirmed the presence of two deeply divergent mitochondrial clades in the Sierra Nevada. Based on acoustic and morphometric differences concordant with the genetic lineages, two species, Rana muscosa and R. sierrae, were recognized. Analysis of one mitochondrial locus and eight nuclear microsatellite loci in three populations showed that R. muscosa and R. sierrae are narrowly parapatric along the Monarch Divide, without sympatry or significant gene flow detected between them. This work bolsters support for the species designations, and highlights a contemporary geographic barrier to gene flow. At the local scale, population structure was explored in R. muscosa within a single basin using microsatellite loci. Patterns of connectivity and gene flow between sites reflected geography, hydrology, and history within the limited area. To understand geographic variation within the wide range of the Pacific Treefrog (Pseudacris regilla ), I tested freeze tolerance and its effects on blood chemistry in low and high elevation frogs. Lowland frogs survived freezing in subzero temperatures, but for shorter durations than their highland counterparts. The geographically restricted Shasta Salamander (Hydromantes shastae) was found to have strong mitochondrial and nuclear genetic divergence between three major clades. These clades show concordant morphometric differentiation, supporting recognition of these species. The five studies presented here highlight the utility of assessing concordance in multiple markers at various spatial scales, and have provided insights into the differentiation of amphibians in California.