I use genetic and analytical tools to investigate how environmental, ecological, and evolutionary processes shape biodiversity. I am particularly interested in understanding how short and long-term interactions between organisms and their changing environment (e.g., meandering rivers, climate, roads, the shape and amount of habitat, etc) can promote (or counteract) genetic divergence and diversity. Below are some projects I have recently been working on.

Mechanisms underlying patterns of diversification and gene flow in the southeastern US

For my dissertation, I studied spatial patterns of genetic variation in a wide-ranging lizard species from the southeastern US, Scincella lateralis (aka ground skinks), to test hypotheses about the environmental forces that shape evolutionary history. By applying population genetic and phylogenetic models to a large multilocus dataset I found evidence that

1) ground skinks have been somewhat isolated by major Gulf Coast rivers, resulting in several genetically divergent (though, morphologically similar) lineages,
2) climate change in the past (i.e., during the Pleistocene) may have interacted with rivers to increase river barrier effects by intermittently restricting ground skink habitat to regions below river headwaters,
3) gene flow continues among many ground skink lineages and is likely higher today than in the past, and
4) passive transfer of ground skinks across rivers due to meander loop cutoff events may contribute to this recent gene flow across major southeastern rivers.

I plan to continue this work by investigating several ground skink contact zones, delimiting species boundaries within the group, and exploring the role of climate change in mediating phylogeographic diversification in the southeastern US by applying past and present niche models to datasets from ground skinks and other codistributed taxa.

How does landscape heterogeneity shape genetic variation and structure of populations?

Environmental change on much smaller temporal and spatial scales can still have dramatic effects on patterns of genetic variation, which influence the survival prospects of populations and species. Working with Lenore Fahrig at the Geomatics and Landscape Ecology Laboratory at Carleton University, I have been developing individual based simulation models to test hypotheses about how the structure of landscapes (e.g., the amount and configuration of habitat, presence of roads, etc) regulate genetic variation and structure of populations, as well as the spatial scale at which this plays out. I am also interested in exploring how species traits (e.g., dispersal or reproductive behavior) mediate these landscape-species relationships.

Phylogeographic model selection

I am currently working with Brian O'Meara at the University of Tennessee and Bryan Carstens and Ariadna Morales-García at Ohio State University on a new method for phylogeographic model selection (called phrapl). Phrapl estimates species relationships and boundaries while simultaneously selecting the most likely demographic model (e.g., effective population size and migration rate parameters) underlying diversification. This ensures that species relationships and boundaries are inferred under the model of gene flow and drift that best fits the data. We are currently comparing the performance of phrapl in species delimitation and model selection with other available approaches using both simulated and empirical datasets.