POPULATION GENETIC-STRUCTURE OF NORTH-ATLANTIC, MEDITERRANEAN SEA ANDSEA-OF-CORTEZ FIN WHALES, BALAENOPTERA-PHYSALUS (LINNAEUS 1758) - ANALYSIS OF MITOCHONDRIAL AND NUCLEAR LOCI

Samples were collected from 407 fin whales, Balaenoptera physalus, at four North Atlantic and one Mediterranean Sea summer feeding area as w ell as the Sea of Cortez in the Pacific Ocean. For each sample, the se x, the sequence of the first 288 nucleotides of the mitochondrial (mt) control region and the genotype at six microsatellite loci were deter mined. A significant degree of divergence was detected at all nuclear and mt loci between North Atlantic/Mediterranean Sea and the Sea of Co rtez. However, the divergence time estimated from the mt sequences was substantially lower than the time elapsed since the rise of the Panam a Isthmus, suggesting occasional gene flow between the North Pacific a nd North Atlantic ocean after the separation of the two oceans. Within the North Atlantic and Mediterranean Sea, significant levels of heter ogeneity were observed in the mtDNA between the Mediterranean Sea, the eastern (Spain) and the western (the Gulf of Maine and the Gulf of St Lawrence) North Atlantic. Samples collected off West Greenland and Ic eland could not be unequivocally assigned to either of the two areas. The homogeneity tests performed using the nuclear data revealed signif icant levels of divergence only between the Mediterranean Sea and the Gulf of St Lawrence or West Greenland. In conclusion, our results sugg est the existence of several recently diverged populations in the Nort h Atlantic and Mediterranean Sea, possibly with some limited gene flow between adjacent populations, a population structure which is consist ent with earlier population models proposed by Kellogg, Ingebrigtsen, and Sergeant.