Biogeography & Conservation Genetics of Gliding Mammals

A major focus of my reseach program is the biogeography and conservation genetics of mammals that are forest canopy specialists, especially gliding mammals. I have worked most extensively on flying squirrels. Like most gliders, flying squirrels are so highly adapted to life in the forest canopy that they can’t persist in unforested areas. Although they do routinely come to the ground to forage, they are not likely to move across large open areas. As a result, they are sensitive to the creation of gaps in forest habitats. On an evolutionary time scale, this means that changes in the distribution of forests have had a profound effect on the biogeography of flying squirrels. On an ecological time scale, this means that flying squirrel movement and distribution patterns are strongly influenced by natural and human-induced forest fragmentation.

I have used genetic data to examine the effects of forest fragmentaion on flying squirrels at multiple spatial and temporal levels. On a continental scale, I have examined the systematics and biogeography of both North American species of flying squirrel (genus Glaucomys). On a more regional scale, I have studied the conservation genetics of two endangered subspecies of the northern flying squirrel ( G. sabrinus) that are restricted to high-elevation remnant patches of boreal forests in the southern Appalachian Mountains of the eastern U.S. I have collaborated on this work with Peter Weigl (my doctoral advisor) and Robert Browne of Wake Forest University.

I am currently working with my Graduate Student, Nick Kerhoulas, to extend our large-scale biogeographic studies of Glaucomys to the flying squirrels of Mexico and Central America. We are using DNA obtained from museum study skins to see how these populations are related to those in North America, and to better understand the biogeography of the New World flying squirrels and the forests they inhabit.

I am also collaborating with Andrea Taylor of Monash University and Ken Aplin of the Australian National Wildlife Collection/CSIRO to study the conservation genetics and biogeography of the world’s largest gliding marsupial, the greater glider, Petauroides volans.

Conservation Genetics of Non-Gliding Arboreal Mammals

I have also worked with my former Graduate Student, Jessica Blois , to examine the conservation genetics of the Sonoma tree vole. This species is also a canopy-specialist (although not a glider). It is a specialized feeder on the needles of the Douglas-fir tree, and rarely comes to the ground. As a result, this species is thought to be especially sensitive to the destruction and fragmentation of Douglas-fir forests. It also has a very small range, occurring only in northwestern California.

Evolutionary Diversification of Galápagos Mockingbirds

In 2006, my colleagues (Dave Anderson, Sergei Drovetski, Peter Boag, Peter Grant, Rosemary Grant, Gilles Seutin and Bob Curry) and I published the first molecular systematic study of the Galápagos mockingbirds.  These birds hold a special place in the history of evolutionary biology, as they were the group that sparked Darwin’s initial insights into speciation and adaptive radiation. Using mitochondrial DNA sequences from population samples of mockingbirds from throughout the Galápagos and mainland South America, we examined the geographic and evolutionary origins of Galápagos mockingbirds, as well as patterns of diversification within the archipelago. This paper was the cover article for the March, 2006 issue of the journal Evolution. It was also noted as an editor’s choice of the literature in the journal Science

I am currently involved in an NSF-funded project lead by Irby Lovette of the Cornell Laboratory of Ornithology to investigate broader phylogenetic relationships within the bird Family Mimidae (mockingbirds, thrashers and their relatives). Multigene phylogenies are being used to examine patterns of adaptive radiation, song mimicry and cooperative breeding in mimids.

Comparative Phylogeography of Boreal Forest Mammals

A major focus of my research is the comparison of spatial and temporal patterns of evolutionary diversification (comparative phylogeography) in mammals inhabiting the northern coniferous forests of North America. I began studying this topic on a large geographic scale as a graduate student, and I continue working on it with my former post-doctoral advisor, Dr. Jim Kenagy of the Burke Museum at the University of Washington. Current work focuses on the Pacific Northwest. We are studying the genetic structures of about a dozen species/species pairs from coniferous forests of the Cascade, Olympic, Blue and Okanogan Mountains of Washington, Oregon and British Columbia. By comparing the population genetic structures of these species, and using multi-locus computational approaches to estimate the timing of diversification events, we will be able to reconstruct how this entire ecological community responded to the major climatic shifts of the Pleistocene, which included at least 20 ice-ages. To find out more about this work, as well as other research being conducted in the Mammalogy Program at the UW Burke Museum, please visit their site.

Phylogenetic and Population Genetic Theory

I also have a strong interest in theoretical phylogenetics, population genetics and molecular evolution. These aspects of my research emphasize the use of maximum likelihood and Bayesian approaches to statistically evaluate evolutionary hypotheses. My work in this area has included the statistical evaluation of competing models of molecular evolution, estimating rates of molecular evolution and testing for differences in rates among organisms, and examining the correlation between Pleistocene climatic changes and patterns of geographic variation and speciation in North American birds and mammals.

One of my more influential publications in this area focused on using molecular clocks to date evolutionary events. I co-authored this paper with Scott Edwards and John Wakeley (both of Harvard University), Peter Beerli (Florida State University), and the late Joe Slowinski (formerly at the California Academy of Sciences).

Arbogast B. S., Edwards S. V., Wakeley J., Beerli, P. and Slowinski, J. B. 2002. Estimating Divergence Times from Molecular Data on Phylogenetic and Population Genetic Timescales. Annual Review of Ecology & Systematics 33: 707-740.