I am an evolutionary biologist and biogeographer who uses natural history specimens to understand patterns of macroevolution and ecological interactions in phylogenetic and spatial contexts. I am particularly interested in research questions that synthesize multiple different types of data from natural history specimens, including skeletal morphology, molecular data, and parasite diversity. Most of my research is performed on the ecologically diverse and species rich rodents and shrews native to the North American southwest and the Philippines.

Islands on Islands: Biogeography of Madrean Sky Island Mammals, Parasites, and Viruses

The Madrean Sky Islands of Arizona, New Mexico, Sonora, and Chihuahua form approximately 42 mountains within the geologic Basin and Range province of Western North American, a region that straddles the Colorado Plateau to the north and the Sierra Madre Occidental to the south. These islands consist of isolated patches of high-elevation oak woodland and conifer forest in a lowland "sea" of Sonoran and Chihuahuan desertscrub and semidesert grassland.

The small mammals (rodents and shrews) on these islands exhibit almost complete species turnover from base to peak, coinciding with major shifts in climate and plant communities. The patterns of inter-mountain connectivity have been poorly studied in most taxa, and remain unstudied from a phylogeographic perspective in small mammals. Along with patterns discernible from the mammals themselves, almost nothing is known about the diversity of and relatedness among the different parasites and viruses who use the native small mammals as hosts.

I am collaborating with researchers at Arizona State University and the Field Museum of Natural History to explore these questions and others using the small mammals of the Madrean Sky Islands. Our team is currently conducting a pilot study in the Santa Catalina Mountains just north of Tucson, collecting voucher specimens and tissue and fecal samples to provide a case study of how the small mammals, ectoparasites, and viruses vary across elevation, with particular interest in patterns of population structure and signals of historical population bottlenecks and future genetic trends given climate change trajectories.

Patterns of Colonization and Speciation in the Northern Philippines

The Philippine archipelago consists of over 7,500 islands that vary in area, age, and peak elevation. They also vary in terms of the number of endemic small mammals. The vast majority of small mammals are single-island endemics: found on one island and nowhere else in the world. Recent developments in island biogeography theory have emphasized the role geologic dynamism and in situ speciation play in determining island species richness, but the systems this model was developed for are typically much smaller and younger oceanic hot-spot archipelagos than the Philippines, which is a comparatively large, ancient plate-margin archipelago. In collaboration with researchers at several institutions across the United States and the Philippines, I am studying the temporal patterns of island small mammal species richness accumulation across four different islands of varying area and age to determine to what extent the patterns of colonization and speciation fit the General Dynamic Model of island biogeography and determine whether the rate of speciation and colonization among these four islands is changing over time.

Ecological Incumbency and the Macroevolution of the Luzon Island "Old Endemic" Rodents

The endemic rodents of Luzon Island, the largest, oldest island in the Philippines, comprise six independently colonizing lineages of members of subfamily Murinae. Of these, the two oldest clades are also the two who have undergone the most in situ speciation: the cloud rats of tribe Phloeomyini and the earthworm mice of tribe Chrotomyini. These two tribes colonized several million years apart, setting up the prediction that tribe Phloeomyini, as the incumbent murine lineage of Luzon, may have had time to diversify to exploit limited habitat and food resources and prevent Chrotomyini from exhibiting their full evolutionary potential. I examined the potential impacts of the ecological incumbency of Phloeomyini on the ability of Chrotomyini to diversify in terms of both species richness and mandible shape and found, contrary to expectations, that Chrotomyini and Phloeomyini have been able to diversify rather uninhibited, but that the areas in which they diversify in their diet exhibit next to no overlap, and this overlap is consistent with ancestral distinction at the point when Chrotomyini initially colonized the Philippines.