Mitochondrial and microsatellite DNA analyses of harbour seal population structure in the northeast Pacific Ocean

The genetic diversity and population structure of harbour seals (Phoca vitu lina richardsi) along the coasts of British Columbia and parts of Alaska we re investigated using both mitochondrial DNA (mtDNA) and nuclear DNA. A 475 -bp fragment of the mitochondrial control region was amplified and sequence d from 128 animals. Sixty variable sites defined 72 mtDNA haplotypes with p airwise nucleotide differences as high as 5%. Fifty-eight haplotypes were r epresented by a single individual, and shared haplotypes were generally res tricted to a small geographic range. Phylogenetic reconstruction revealed t wo distinct populations comprising (i) southern British Columbia and (ii) n orthern British Columbia - southeast Alaska. Furthermore, the order of the clades suggests that the Pacific Ocean was colonized at least twice, 670 00 0 and 380 000 years ago. Haplotypes from the first invasion are restricted to a small number of seals around southern Vancouver Island. Analyses of fi ve polymorphic microsatellite loci showed significant differences between t he populations of southern British Columbia and northern British Columbia - Alaska. Migration rates for males based on microsatellite data (3-22 seals /generation) were higher than those obtained for females from mtDNA data (0 .3 females/generation). Combining all the DNA data collected to date sugges ts that there are at least three populations of harbour seals in the Pacifi c composed of seals from (i) Japan, Russia, Alaska, and northern British Co lumbia, (ii) southern British Columbia and Puget Sound, Washington, and (ii i) the outer coasts of Washington, Oregon, and California. The data do not support the existence of two subspecies of harbour seals in the Pacific Oce an.