Research summary

I study evolutionary biogeography, phylogeography, and molecular systematics, focusing on Southeast Asian and North American mammals. I use DNA data to infer evolutionary and demographic processes. In concert with these empirical questions about natural populations of mammals, I am interested in ways of integrating geographic and genetic data, in using old and new museum specimens in genetic research, and in the behavior of analytical methods in systematics and phylogeography.

Research interests 

tree and map Where a species is found is deeply entwined with its evolutionary history. This partly determines the environmental conditions (including climate), the landscape (including the distribution of habitat and barriers, and major natural features such as mountains and rivers), and the spatial distribution of populations and subpopulations. The goal of my research program is to understand how these spatial factors affect evolution in natural populations. I use DNA to answer these fundamental questions about the origin, maintenance, and distribution of biodiversity across temporal and spatial scales. My research program is inherently specimen-based, and I combine field work with molecular genetics using both new and historical specimens and associated data, and with analytical methods in phylogenetics, population genetics, and geography. These are some of the specific research questions I am currently pursuing.

Analytical methods in systematics and biogeography

How we analyze data is crucial to the inferences we can make about biodiversity and evolution, but we often don't completely understand how our methods behave with real, messy empirical data. I am interested in testing methods and the simplifying assumptions we are forced to make when we use them to answer questions in biology. As a postdoctoral fellow at the National Evolutionary Synthesis Center (NESCent), I am currently working toward a test of bias in common phylogenetic methods used in phylogeography, using a combination of empirical and simulated data.
network I have also done research on the behavior of phylogenetic mixture models and partitioned models, some of which is featured in a 2009 paper in Systematic Biology on treeshrews. How to treat multilocus data is currently a question of great importance in systematics. I am also investigating network methods as an alternative to traditional consensus methods of summarizing trees and support in trees.
I am particularly interested in ways of developing geographic information systems (GIS) and spatial analyses for use with spatially-explicit phylogenetic and phylogeographic data; these methods are now heavily in use in landscape ecology and biogeography but are still relatively rare in phylogenetic analyses. As accurately georeferenced specimen data become more widely available, such analytical geostatistical methods are beginning to transform the geographic component of specimen-based research.

Mammalian evolutionary biogeography

My research program has mainly focused on the mammals of Southeast Asia, a region of high biodiversity and conservation concern across taxa. Through ongoing projects on several groups of mammals and in several subregions, I am addressing questions about the importance of distribution, historical geography, and islands in the evolution of the regional fauna. Some of my study taxa are themselves endangered or threatened, and others provide a natural context for understanding the role climate and habitat change, on short and long timescales, have played in evolutionary history. I have also recently become involved in genetic and phylogeographic research on the enigmatic and endangered monkey Rungwecebus kipunji in Tanzania.
treeshrew chromolithograph

Treeshrew systematics and phylogeography: Understanding geographic variation and diversification

Treeshrews are among the closest living relatives of primates, but the relationships among species and even species boundaries are anything but clear. In collaboration with Link Olson and Eric Sargis, I am studying systematics, biogeography, and phylogeography in this unique and neglected order of mammals. The two current focal questions of our treeshrew research are (1) systematics and the timescale of diversification in the entire order and (2) the distribution of morphometric and mitochondrial DNA variation within the cryptic, diverse Tupaia belangeri/Tupaia glis species group. The validity of most current and former named species and subspecies in this complex is unknown, but their evolutionary history has noteworthy biogeographic and conservation implications.
treeshrew skull Much of our genetic data for this project uses so-called "antique" or degraded DNA from museum specimens, mostly collected between 1890 and 1960. Being able to consistently amplify DNA from museum specimens without destructive sampling is an exciting development, as it may unlock genetic information from a huge number of specimens. Using the Ancient DNA Lab at the University of Alaska Museum, we have developed efficient protocols for "antique" DNA amplification that also minimize the risk of cross-contamination from humans or from other specimens.

Distribution and relationships in Cambodia: Mammals of a neglected region

Cambodian mammals are some of the poorest known in Southeast Asia. Recent specimens are almost nonexistent in museum collections, and only a small handful of any age are in the collections of North American museums. In 2007, with co-PIs Link Olson and Eric Sargis, I acquired funding from NSF to obtain a large collection of Cambodian mammal specimens from the Wildlife Conservation Society in Phnom Penh. As a result, more than 1,100 specimens—more Cambodian mammals than at all other North American museums combined—are now housed at the University of Alaska and available to the international scientific community. Bat specimens in this collection, as well as those resulting from our field work in eastern Cambodia this spring, will form part of my future research on the region’s mammals.

Phylogeography of Philippine fruit bats: Diversity and divergence on islands

The evolutionary history of the highly endemic Philippine fauna remains uncertain, despite its importance in understanding conservation priorities and diversification patterns in the region. My dissertation research focused on the phylogeography of six Philippine fruit bat species. This project mixed molecular systematics with phylogeographic, population genetic, and coalescent analyses, and at that point was the finest-scale genetic study of any Philippine mammals. I discovered several surprising patterns that may be extended to other taxa and areas. Deeply divergent cryptic clades were present in several species, suggesting that some of them are older than had been thought and that community structure has been remarkably stable for millions of years. Divergence time estimation shows that single events may have driven dispersal and divergence in multiple species simultaneously, probably as a result of regional geologic and tectonic upheaval. I also showed that genetic diversity on islands was related to their size and isolation, but that in some cases diversity still reflects past geography.

The mammals of Utah: Phylogeography in the Intermountain West

With collaborators at the Utah Museum of Natural History and the Field Museum, I am studying the evolution and biogeography of small mammals in Utah and surrounding states. As a graduate student, I did field work in Utah for four summers as part of a continuing project led by Rebecca Rowe, Larry Heaney, and Eric Rickart. Using water shrews (Sorex palustris), we have begun to investigate genetic patterns among Utah’s mountain ranges. Surprisingly, our data show that northern Utah shrews are more closely related to those in other northern states (as far north as Alaska) than they are to those in the southern part of the state, although some predicted barriers, such as the Colorado River, do impede gene flow. This has led us to question previous assumptions about the formation of the Utah fauna, and may help us understand patterns of range expansion and contraction as a result of land use and climate change.