Research
Program
My lab focuses on exploring the factors that shape biological diversity at the level of individuals and populations. Through investigation of environmental variation and fine-scale biogeography, we are interested in understanding variation in organismal traits (e.g. physiological performance, life history, and disease resistance) and the demography of populations. To study these relationships we use an approach that combines characterization of genetic variation using molecular markers with fieldwork to describe the ecological context for evolutionary change. Most often amphbians and reptiles are the organisms that capture our interest. Further details of recent and ongoing projects in the lab are described below.
Molecular
Ecology of Galápagos
Lava Lizards (Microlophus spp.)
A central goal of evolutionary biology is to understand the origin and maintenance of genetic and phenotypic diversity. Studies of populations resident on oceanic islands have provided critical insight into these processes. Galápagos lava lizards are a group that lends itself to rigorous evolutionary study in this tradition. Populations of lava lizards are distributed across an array of islands and islets that are geographically proximate and share a well-defined geological history. Considerable variation in morphology, life history, ornamentation and physiological performance exists within and among these populations. We have shown that gene flow is unlikely to limit phenotypic divergence within a small island that exhibits a marked shift in habitat structure. Meanwhile, genetic drift in isolation is strongly implied in populations that were fragmented when sea levels rose following glacial melting at the end of the Pleistocene. These results suggest that an interaction between drift and selection is likely to have shaped the recent diversification of these lizards.
Conservation
Genetics of a Terrestrial Salamander
Amphibian species have experienced a drastic decline in suitable habitat in the Midwest over the past 200 years. Fragmentation of the landscape due to conversion of land for agricultural use, the development of roads, and urbanization is expected to restrict dispersal among populations. This isolation should decrease genetic diversity at local sites thereby increasing extinction risk and reducing the potential for adaptive diversification. We have been investigating the effect of habitat loss using a terrestrial salamander, Plethodon cinereus, found in isolated woodlots in northeast Indiana. P. cinereus is a good candidate for this type of study due to its strong territoriality and acute physiological dependence on the cool, moist microhabitats found in forests. Our results suggest that although genetic diversity is low across the region, the pattern of genetic differentiation among populations appears to fit a model of post-Pleistocene range expansion rather than recent population decline.
Evolutionary Ecology of Ranaviral Infection in 
Midwest Amphibians
Disease emergence is one of many factors that has been implicated in the decline of amphibian populations. Population loss in amphibians native to western North America and the United Kingdom have been linked to outbreaks caused by members of the genus Ranavirus. While it is hypothesized that virulent strains from this group originate from eastern North America, little is known about the ecology of ranaviral infection in amphibians native to the region. We are working to address this knowledge gap in the following ways by: 1) screening potential host species for the presence of infection in NE Indiana, 2) conducting challenge experiments in local species to assess the virulence of strains known to cause outbreaks elsewhere, 3) determining whether the genetic background of infected individuals is associated with resistance, and 4) correlating water and habitat quality with the incidence of infection in a watershed dominated by agricultural activity. These studies are being conducted in collaboration with colleagues at IPFW (Bob Visalli and Bob Gillespie) and Purdue main campus (Andrew DeWoody and Rod Williams).
