Curator of Birds, Burke Museum of Natural History and Culture
Don and Betts Baepler Endowed Professor, Department of Biology
University of Washington
Phone: (206) 685-7201
Much of my research involves using DNA sequences to reconstruct phylogenetic hypotheses of avian relationships. Such phylogenies, the cornerstone of modern comparative methods, provide a necessary framework for studying the evolution of various avian traits. Characters examined in this context can include behaviors (such as migration), morphological traits (such as size, osteological characters, or plumage coloration), or distributions through time and space (biogeography). The latter is the focus of much of the research done in my lab, where we begin by identifying the units of biodiversity and then attempt to understand the origin and maintenance of this diversity in an ecological and biogeographic context.
As a research scientist during the past 12 years, I have been pursuing three related lines of inquiry:
- Where earlier taxonomists used morphological, behavioral, and vocal characters to delimit species and define the relationships among them, we are using molecular characters. As part of a NSF-funded study (NSF DEB 0315469) on the “avian tree of life”, my collaborators (from three additional institutions) and I generated, compiled, and analyzed a multilocus data set that included all representatives of the most speciose New World avian clade (nine-primaried oscines [i.e. “songbirds”], ~823 species), yielding for the first time a robust phylogeny for this well-known group of birds. As a result of this work, songbird taxonomy is being rewritten and researchers now have a reliable basis for comparative study.
- In a second line of research I am collaborating with Drs. Garth Spellman and Scott Edwards on a comparative phylogeographic study (NSF DEB 0815057) of birds that co-occur in montane pine and pine-oak habitats (“sky-islands”) of western North America. We are using a multilocus data set and a population-genetic and coalescent approach to determine whether the birds breeding in these habitats are structured into genetically and geographically discrete evolutionary units. Two-thirds of the 21 species examined possess two or more such units. Thorough geographic sampling will allow us to assess the magnitude and direction of gene flow occurring between them. The results of this work have important conservation and management implications but also allow us to ask how common patterns of genetic diversification across this suite of co-distributed species can be interpreted in light of known episodes of change in earth history (e.g. glacial advances, regional uplifting, etc.).
- A third focus of my research involves genetic sampling across multiple lineages of tropical birds from throughout their ranges in Central and South America. In this work, I am investigating how the Isthmus of Panama completion some three million years ago affected diversification rates in this region, and more generally, how the “Great American Interchange” played out for avian taxa. Our preliminary results contradict the widely accepted notion that because birds can fly, they did not require the presence of a land bridge to move between continents. We show instead that the Panamanian uplift greatly affected avian lineages in the neotropics and that intercontinental patterns of dispersal and diversification for birds are remarkably similar to the well understood patterns observed for mammals.
My future research will involve some extension of current research ideas and a few new directions. I have only scratched the surface of what can be done with the genetic samples already on hand from the western “sky-islands” study. This work will be extended to focus more narrowly on the nature and extent of identified hybrid zones. Hotspots of introgression for this suite of birds include the Okanagon Valley (NE WA), Blue Mountains (NE OR), and foothills along the eastern slope of the Sierra Nevadas. These could be examined more closely (and also in a comparative framework) using multilocus data generated using next generation sequencing technologies, in combination with niche modeling. These tools would allow us to examine the relative breadth of hybrid zones, assess genetic compatibility, and look for ecological differences and evidence of local adaptation. This sky-island system and the data already generated also lend themselves well to a regional study of climate change. Genetic profiles can be established, demographic statistics calculated, and degree of isolation assessed for populations across the Great Basin. Modeling of various climate change scenarios should shed light on how global warming will impact connectivity among widely spaced isolated mountain-top populations and how these changes might affect the genetic composition and ultimate fate of each population.
The research described above revolves around DNA labwork and phylogenetic analyses but it begins with fieldwork. Within the Burke Museum ornithology group, specimen-based research is emphasized. Birds collected and prepared as specimens during field expeditions contribute not only to our own research programs but they also provide a valuable resource that is available to the general ornithological community.