Molecular phylogenetic approaches are used to test hypotheses regarding biogeography, trait evolution, and species boundaries and relationships. Previous and ongoing research has examined the phylogenetic relationships, systematics, and biogeography of the bufonids (the true toads). Other studies have focused on species delimitation and phylogeographic patterns among closely related taxa or within a particular species. Recent and ongoing research includes studies of phylogeography and species delimitation in amphibians of the western US, comparative biogeographic patterns in salamanders and turtles of the southeastern US, and phylogeographic patterns in Australian freshwater turtles.
Much of the phylogenetic and phylogeographic work described above focuses on species of conservation concern. Here, molecular genetic techniques and morphological analyses are carried out to inform the management and conservation of declining species. Questions addressed include understanding species boundaries, assessing hybridization, and estimating gene flow and migration rates among populations of declining species. Current projects focus on red-legged frogs, Western Toads, and Yosemite Toads in California as well as Alabama Red-bellied Turtles and Flattened Musk Turtles in the southeastern US. The red-legged frog and turtle projects are collaborations with Brad Shaffer and his lab at UCLA and the Alabama Red-bellied turtle work is a collaboration with Jim Godwin at Auburn University.
For most frogs, the primary mating signal is the advertisement call, and the production of these calls is the most energetically demanding activity in which a male frog will ever engage. Plus calling exposes frogs to eavesdropping predators and parasites. Previous and ongoing studies have examined the function of the anuran vocal sac as well as the evolution of the advertisment call in the Western Toad species group in which several species have lost the ability to produce advertisment calls.
Habitat loss and alteration due to urbanization presents one of the greatest threats to native species. I have been examining impacts of urbanization on Western Pond Turtles in California since 2000 and on Blotched Watersnakes in Texas since 2006. Much of the pond turtle work focuses on impacts of non-native taxa, particularly the red-eared slider which is the most common turtle in the pet trade, the most commonly introduced turtle world-wide, and now on the IUCN list of "100 of the World's Worst Invasive Alien Species." The watersnake work, a collaboration with Dr. Travis LaDuc at the Texas Memorial Museum, examines movement patterns and population demography along a heavily urbanized stream. New projects in the Los Angeles area include assessing correlates of amphibian and reptile distribution as part of the Lost Lizards of Los Angeles Project and assessing urban turtle diversity.