Patterns of genetic variation in North Atlantic blue whales (Balaenoptera musculus): Population diversity, differentiation and demographic history analysis of mitochondrial and nuclear loci

Understanding the population diversity, differentiation and demographic history is important to define evolutionarily significant units and management units. Although endangered, little is known about these parameters in blue whales, (Balaenoptera musculus). Based on whaling and photo-identification data in the North Atlantic at least two populations of blues whales have been identified; an eastern ranging from the Icelandic waters to Northwest Africa, and a western ranging from West Greenland to eastern North American sea border. Samples were collected from 238 blue whales from the Gulf of St. Lawrence and West Greenland. A total of 300 base pairs of the mitochondrial (mtDNA) control region were sequenced and the genotypes at multiple microsatellite loci will be analyzed. The nucleotide diversity at the mtDNA was estimated at 0.9% and the heterozygosity at four microsatellite loci was at 75.4% which in the same range as other North Atlantic rorquals, except the humpback whale. The preliminary results reveal no significant levels of divergence at mtDNA or four microsatellite loci between localities within the western North Atlantic. An analysis of longterm population genetic equilibrium did not reveal any statistically significant deviations at mtDNA or nuclear loci suggesting a constant population size and a neutral mode of evolution. However, the mismatch distribution estimated from the mtDNA sequences fit the Rogers model of population under expansion better than a Watterson model of a constant size population. Using alleles frequencies we are exploring nuclear loci patterns to interpret demographic history (detecting expansion or bottleneck). The use of both mtDNA and nuclear loci will allow us to provide some insight into these evolutionary processes