Mitochondrial DNA control region sequence variation in Common Eiders reveals extensive mixing of subspecies

We sequenced a hypervariable 319 bp portion of the control region of mitochondrial DNA in five subspecies of Common Eiders (Somateria mollissima) and an outgroup sample of King Eiders (S. spectabilis). Variation was found at 71 sites (22%), which defined 56 haplotypes in the total sample. A genealogical tree relating the haplotypes revealed three major clades, but with the exception of Common Eiders (S. v-nigra) from Alaska, they did not correspond with putative subspecies identities. No geographic structuring was apparent, and the detection of an Alaskan genotype in one bird collected in Labrador suggests that long-distance dispersal occurs. A molecular clock calibrated for control region I suggests that the major clades have originated within the last 300,000 years or so, and that there has been mixing of historically separated populations as the Arctic was recolonized relatively recently. To independently test this hypothesis and to check for male-biased dispersal, we will report preliminary results from biparentally transmitted nuclear markers at microsatellite loci. Future work needs to bebased on samples collected on the breeding grounds to obviate problems with winter mixing of populations.