Mitochondrial DNA Lineages in Composite Flocks of Migratory and Wintering Dunlins (Calidris alpina)

Abstract

Mitochondrial DNA (mtDNA) control-region sequences of 52 migratory and wintering Dunlins (Calidris alpina) from around the world were determined with direct sequencing of PCR products. The genetic lineages detected in these birds are identical to those found previously in a much larger sample of 155 breeding Dunlins from their northern circumpolar range. Samples of nonbreeding Dunlins from both sides of the Pacific reveal a mixture of two lineages that breed separately in eastern Siberia and Alaska. The presence of Dunlins with an eastern Siberian haplotype along the west coast of North America indicates that the Bering Strait does not represent a biogeographic barrier to Dunlin migration. Dunlins wintering in eastern Asia most likely originated from the discrete breeding population in northern Alaska because they possess haplotypes that were found predominantly in birds from this region. Similarly, Dunlins from staging and wintering sites in Europe and western Asia reveal a mixture of two mtDNA lineages that were previously found confined largely to European and central Siberian breeding grounds. Limited gene flow between these breeding areas, however, precludes definitive allocation of individuals to their population of origin on the basis of mtDNA analysis alone. Body mass, time of migration, and molting pattern seem to be associated with the mtDNA types of migratory Dunlins in Europe, but data are too sparse to determine whether these characters are useful adjuncts in assigning nonbreeding birds to populations that correspond to the major genetic lineages. Overall, the genetic composition of nonbreeding populations indicates the confluence of breeding populations on southward migration. Because of strong phylogeographic population structure in Dunlins on their breeding grounds, mtDNA analysis can be extremely useful in defining broad migration corridors or flyways, and in determining staging and wintering areas used by the major breeding populations.