Speciation in Landscapes of Gene Flow
Our understanding of the speciation process is limited in many vertebrates, especially for morphologically similar, geographically overlapping, and occasionally hybridizing lineages. Using a near-globally distributed rodent group as a model (squirrels; Family Sciuridae), we are investigating variation in species traits potentially important for speciation, including shape and size of the baculum (the highly variable male genital bone). This project integrates phylogenomics, high-resolution CT scanning of bacula, and phenotypic and biogeographic analyses to forge new links between landscape-level trait variation and the evolution of reproductive isolation.
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Comparative Phylogeography of Desert Mammals
Using genomic tools, we are working to understand the landscape-level processes (gene flow, historical biogeography and demography) shaping the genomes of desert rodents inhabiting cold-winter deserts on different continents (Great Basin Desert in North America, Gobi Desert in Asia - largely Mongolia). Compared to North American systems, impacts of past climate change on Central Asian mammals in particular are poorly known. This cross-continental work involves specimen-based approaches as well as ongoing field expeditions to better understand impacts of past and present climate changes on mammals in these sensitive regions.

Essential Mammal Traits and Global Change 
There is increasing evidence that climate change is impacting not only the distributions and genetic diversity of species, but also core ecological and life history traits. Unfortunately, records of these effects are sparse for mammals, many of which are nocturnal and difficult to observe. Using a variety of data sources, we are building spatiotemporally explicit databases that document variation in core life history traits of common North American small mammals (Peromyscus, Microtus, Clethrionomys) over the past century, and using these to link species traits to climate variables and more effectively track species responses to global change drivers.

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Ground Squirrel Speciation and Global Change
I am working to resolve the species-level phylogeny of ground-dwelling squirrels, a diverse group (> 90 species) of rodents distributed across North America and Asia. These projects use novel genomic-scale datasets (whole mitogenomes and UCEs) collected from museum samples to reconstruct phylogenetic relationships and understand the structure and timing of ground squirrel diversification in relation to past climate warming and global expansion of grasslands.