Evolutionary history and migration patterns in the yellow warbler (Dendroica petechia)

An emerging application of phylogeography in avian conservation is to use the genetic structure revealed by the DNA markers as a "genetic tag" to track migratory birds throughout their annual cycle. I used inferences from genetic analyses to show how the Pleistocene glaciations have moulded the evolutionary history of a migratory bird, the yellow warbler ( Dendroica petechia). Based on mtDNA genotypes from 696 breeding birds, I found two monophyletic clades: a highly migratory clade consisting of eastern and western lineages and a less migratory clade consisting of southern and resident lineages. This result is not consistent with the current taxonomy of the species that is primarily based on plumage variation: The eastern (central and east North America) and western (central and west North America) lineages overlapped less extensively in the United States than in Canada due to the isolating effect of the US Central Great Plains. Since the eastern, southern, and western lineages were geographically structured on the breeding grounds, I used genetic differences between lineages as "genetic tags" to establish linkages between breeding, migrating and overwintering populations. I found strong migratory connectivity between lineages: the eastern lineage was present in central and east North America during migration and in Central America and Venezuela during the winter; whereas the western lineage was present in central and west North America during migration and in Mexico and Central America during the winter. This provides evidence for a parallel migration system in these birds. Finally, based on stable-hydrogen isotope analysis of flight feathers, birds from latitudinally distinct breeding areas tended to migrate together in most stopover sites but a leap-frog pattern was present in Alabama during fall migration. In terms of conservation implications, I suggest that Neotropical bird migrants could be managed using phylogeographic flyways to define management units.