What is a species and how do we recognize it? I am interested in patterns and processes of species formation. I use molecular data and tools from the fields of systematics and phylogeography to delineate boundaries within complexes of ‘cryptic species’ (two or more species erroneously classified as single species). My research has shown that many geographically widespread ‘species’ of frogs in Southeast Asia actually contain multiple, divergent, and sometimes sympatric evolutionary lineages that I hypothesize to be distinct species. These findings have implications for biogeography, community ecology, and conservation, and raise questions on how these sympatric lineages originated and are maintained.
There is a pressing need to describe species diversity to provide conservation managers with information that can help mitigate loss of biodiversity from human activities. This is a critical role that systematists can take in the fight to preserve global health. I prepare species descriptions and taxonomic revisions of amphibians and reptiles, usually initiated by discoveries that I make during fieldwork. To date, I have described over 30 species of Southeast Asian amphibians and reptiles.
Bridging my interests in molecular systematics, phylogeography, and specimen-based taxonomy, I am excited by developments toward recovering usable DNA from preserved (including formalin-fixed) museum specimens. The vast majority of existing museum specimens of amphibians and reptiles were prepared prior to the molecular revolution, and therefore lack associated tissues that were preserved for molecular analyses. As a graduate student, I successfully modified a human forensics protocol to obtain mitochondrial and nuclear DNA from museum specimens of frogs, turtles, and amphisbaenians that were preserved as far back as the mid-1800s. I am optimistic that next-generation DNA sequencing technology will greatly advance these efforts.
Emerging Infectious Diseases
Four emerging pathogens, the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd), the salamander chytrid fungus B. salamandrivorans (Bsal), the snake fungus Ophidiomyces ophiodiicola (Oo), and Ranavirus (principally Frog virus 3; FV3) have been associated with morbidity, mortality and/or mass die-offs of wild populations of amphibians and reptiles around the world. These emerging pathogens have been human-mediated, either directly through commerce of amphibians and reptiles for pets, food, traditional medicine, and research, or indirectly through increase of environmental stressors. North Carolina has a very high diversity of amphibians and reptiles (notably, the state is a global hotspot of salamanders), but the presence and impact of these emerging pathogens are undocumented or poorly understood in the state. I am collaborating with field herpetologists, molecular biologists, veterinarians, state agency managers, and citizen scientists to test if Bd, Bsal, Oo, and FV3 are emerging pathogens in wild and captive amphibians and reptiles in NC, especially species undergoing population declines in the region. Identifying these pathogens in wild amphibians and reptiles across NC will be critical for understanding the ecology of these diseases, and will be essential for monitoring, management and conservation practices.
I have maintained an active field program in Southeast Asia since I began working with the Wildlife Conservation Society Laos Program in 1998. My field program in Southeast Asia focuses on the countries of Laos, Cambodia, Thailand and Vietnam. The amphibians and reptiles of Laos and Cambodia are very poorly known, and most of my field efforts have been in those two countries. This fieldwork often entails logistically challenging expeditions to very remote areas.
I live and work in the beautiful U.S. state of North Carolina, home also to at least 164 species of amphibians and reptiles (here is a recent checklist). My fieldwork in North Carolina is primarily focused on improving genetic resources at the North Carolina Museum of Natural Sciences by obtaining voucher-associated tissue samples of amphibians and reptiles across the State. I have a particular interest in field sampling of two-lined salamanders (Eurycea bislineata complex) in support of a project on the taxonomic identity of the population in the Sandhills of North Carolina, and in field sampling of slider turtles (Trachemys scripta complex) in support of a project on extent of hybridization between the native yellow-bellied slider and the invasive red-eared slider. My fieldwork in North Carolina is also focused on obtaining samples to test for the presence of emerging infectious diseases in amphibians and reptiles.
My research has been supported by the North Carolina Museum of Natural Sciences, and by grants from the U.S. National Science Foundation, the John D. and Catherine T. MacArthur Foundation, the National Geographic Society, and the Triangle Center for Evolutionary Medicine (TriCEM).