Journal of Heredity Advance Access published online on May 8, 2008
Journal of Heredity, doi:10.1093/jhered/esn025
Phylogeography of a Widespread North American Migratory Songbird (Setophaga ruticilla)
From the School of Biological Sciences, Washington State University, Pullman, WA 99164 (Colbeck and Webster); the Department of Evolution, Ecology and Organismal Biology, The Ohio State University, 370 Aronoff Laboratory, Columbus, OH 43210 (Gibbs); the Smithsonian Migratory Bird Center, National Zoological Park, Washington, DC 2008 (Marra); Canadian Wildlife Service, Saskatoon, SK, Canada, S7N 0X4 (Hobson)
Address correspondence to Gabriel J. Colbeck at the address above, or e-mail: gcolbeck{at}mail.wsu.edu.
Genetic analyses for many widespread North American species have revealed significant east–west differentiation, indicating that many survived through the Pleistocene in 2 glacial refugia—1 in the eastern and 1 in the western part of the continent. It remains unclear, however, whether other areas may have served as important glacial refugia. Moreover, many such species exhibit widespread genetic similarity within eastern and western regions because of recent expansion from small refugial populations, making it difficult to evaluate current-day levels of gene flow. In this study, we used mitochondrial DNA (mtDNA) control region sequence and amplified fragment length polymorphism markers to survey genetic variation in a widespread migratory bird, the American redstart (Setophaga ruticilla). mtDNA analyses revealed a pattern that contrasts with that found for most other widespread species studied to date: most redstart populations across North America appear to have spread out from a single glacial refugium, possibly located in the southeastern United States, whereas populations in far-eastern Canada may have survived in a second glacial refugium located on the now-submerged Atlantic coastal shelf off the coast of Newfoundland. A pattern of isolation by distance in mtDNA suggested some constraints on current-day gene flow among extant redstart populations. This study thus reveals a recent evolutionary history for this species that differs from that of most other widespread North American passerines and provides evidence for limited gene flow in a species with potentially large dispersal distances.
Corresponding Editor: Rob Fleischer
Received July 4, 2007
Accepted April 8, 2008