Geographic distribution of mitochondrial DNA haplotypes in grey seals (Halichoerus grypus)

Mitochondrial DNA (mtDNA) variation in grey seals (Halichoerus grypus) was estimated by restriction fragment length polymorphism (RFLP) analysis of samples collected from four geographic locations: the Gulf of St. Lawrencn(n = 24), Sable Island, Nova Scotia (n = 20), Norway (n = 16), and the Baltic Sea (n = 20). In total, 18 haplotypes were identified. Nucleotide diversity was estimated to be 0.0039 for the Gulf of St. Lawrence, 0.0035 for Sable Island, 0.0079 for Norway, and 0.0059 for the Baltic Sea. There were no shared haplotypes between the western North Atlantic and eastern North Atlantic groups, and genetic distances between these populations (2.0–2.4%) suggest that they diverged approximately 1.0–1.2 million years ago. Nucleotide divergence between the Baltic Sea and the Norwegian populations was estimated to be 0.7%, suggesting that separation of these two groups took place much more recently, about 0.35 million years ago. The distribution of mtDNA haplotypes among Canadian grey seals suggests little or no geographic separation between animals breeding in the Gulf of St. Lawrence and those breeding on Sable Island. In addition to providing basic information on stock analysis the grey seal mtDNA RFLP analysis should be of value for further studies including polymerase chain reaction and direct sequence analyses.