My general interests are in phylogeography and conservation of amphibians in the southeastern US. As molecular ecology is a rapidly growing field with the potential to answer a wide variety of questions, I aim to incorporate genetics into all of my work - in particular, exploring the vast opportunities provided by massively parallel, next-generation sequencing methods. I am interested in exploring questions in biogeography and phylogeography, population genetics, systematics, genomics and transcriptomics, and conservation to better understand the patterns and processes of the evolution of biodiversity in the southeastern US.
My research is a model for understanding how geography and climate have influenced current amphibian distributions in the Southeast and how we can use this knowledge to make predictions given future climate projections. Specifically, the overall focus of my research is to understand (1) the evolutionary processes underlying amphibian geographic distributions in the southeastern US., and (2) the effects of climate, landscape, and geography on phylogeny and patterns of genetic variation in southeastern amphibians.
My dissertation research used the southern red-back salamander Plethodon serratus as a model for investigating the processes driving "multi-disjunct" amphibian species ranges in the Southeast. This region is home to at least 30 vertebrate species with these "multi-disjunct" distributions (consisting of 3-10+ isolated regions), including 18 amphibians. I used genetic data and spatially explicit natural history collection and environmental data (through ecological niche modeling and palaeodistribution modeling) to describe the patterns of genetic variation within P. serratus and test hypotheses about demographic and biogeographic history.
Phylogeography of Plethodontid Salamanders
The rationales for including multiple loci in phylogenetic and systematic studies are well established, but the large genomes of amphibians, and particularly salamanders, pose unique challenges for novel methods of generating massive genetic data sets. Salamander genome sizes can be up to 40 times the size of the human genome! Part of my dissertation involved testing the utility and effectiveness of new protocols for next-generation sequencing for generating a large multilocus phylogenetic data set for P. serratus to further elucidate the systematics and evolutionary history of this species.
The family Plethodontidae is one of the most diverse in terms of genome size, with genomes ranging from about 18-70 Gb. There are 55 species of Plethodon, but genome size has been measured for only 25% of those species (which is actually a fairly decent percentage). The genome size of my own study species, P. serratus, was not known, so I collaborated with Ryan Gregory at the University of Guelph to collect this data. On a broader scale, I am using ancestral character reconstruction to study how genome size has expanded and contracted along lineages in Plethodontidae.
Evolution of Genome Size
My master's thesis research investigated the evolutionary history of the widespread species Rana sphenocephala (southern leopard frog). This species has a long, complicated taxonomic history, with two subspecies frequently recognized, one fount only in southern peninsular Florida, and the other found throughout the rest of the species range. I used an integrative approach including phylogenetics, GIS-based ecological niche modeling, and morphology to resolve taxonomic controversy and reconstruct the evolutionary history of R. sphenocephala.
I was also one of two lead researchers on a collaboration among several institutions investigating multiple leopard frog populations of interest in the northeastern U.S. Several populations had mating calls that sounded different from both of the known leopard frog species in the area. Our genetic analyses showed that the region is host to a previously undescribed cryptic species, which we named Rana kauffeldi, the Atlantic Coast leopard frog.