Greg defended his dissertation (successfully) in August 2008, and then took a postdoc in Brad Shaffer's lab at UC Davis.

I am interested in phylogenetic systematics, historical biogeography, phylogeography, and the evolution of mating signals. For my dissertation, I am examining the evolution of the major mating signal, the advertisement call, in North American toads at two different scales. At the broader scale, I am examining the rates and patterns of evolution of morphological, physiological, and behavioral aspects of the advertisement call across approximately 20 species of North American toads. At the finer scale, I am studying sexual selection and call evolution in western toads, Bufo boreas. In this species, populations vary in the production of the advertisement call. While males in some populations produce a loud, long, pulsed advertisement call that is similar to calls of other toad species, males throughout the majority of the species’ range fail to produce these calls. Although intraspecific variation in characteristics of mating signals is commonly observed and expected under a variety of models of sexual selection, variation among populations in the occurrence (i.e. presence/absence) of mating signals is extremely rare. These scenarios, however, provide excellent opportunities to study sexual selection and mating signal evolution. I combine molecular genetic, morphological (studies of the vocal sac and larynx), behavioral (female choice or phonotaxis studies), and natural history studies to discriminate among multiple models of sexual selection in hopes of understanding the selective processes and evolutionary history of mating signals in this species.

Other research interests include conservation of reptiles and amphibians and studies of defensive chemistry. The conservation work has three main foci: 1) phylogeographic approaches to delimiting species boundaries and management units in species of conservation concern (e.g. California Tiger Salamanders, Flatwoods Salamanders, and Red-legged Frogs; 2) genetic diagnoses of introduced populations (e.g. ongoing work examining extralimital populations of Northern Red-legged frogs); and 3) the impact of urbanization and habitat modification on reptiles and amphibians (e.g. studies of turtles and blotched water snakes in heavily urbanized environments and human-mediated range expansions in sharp-tailed snakes). Studies of defensive chemistry involve the possible sequestration of defensive compounds from an introduced slug by sharp-tailed snakes (in collaboration with Julie Ray and Alan Savitzky at Old Dominion University) and the evolution of defensive compounds in toads (in collaboration with Jim Fordyce at the other UT—the University of Tennessee).