Genetic connectivity of the South American fur seal (Arctocephalus australis) across Atlantic and Pacific oceans revealed by mitochondrial genes

South American fur seals, Arctocephalus australis, were intensively hunted for centuries, leaving the species at the edge of extinction. After the cessation of commercial hunting in the 20th century the overall population has increased to an estimated population of 250 000–300 000 individuals, with Guafo Island being the largest breeding colony in Southern Chile with Guafo Island in Southern Chile being the largest breeding colony. The genetic diversity of the South American fur seal population on Guafo Island and the possible genetic connectivity among populations from the Atlantic and Pacific oceans were studied in order to assess the importance of the Southern Chile Pacific population for the management of the species. Mitochondrial DNA sequences from the Guafo Island population were compared with those from various Atlantic (Brazil, Uruguay, and Argentina) and Pacific (Peru) populations previously studied. The results indicate the occurrence of historical and/or current gene flow among the populations of Guafo Island in the Pacific Ocean and the populations of the Atlantic Ocean, displaying a lack of genetic structure within these areas. In contrast, the Peruvian population is highly divergent compared with the Chilean and Atlantic populations. The lack of genetic structure of Guafo Island fur seals suggests that this group is connected to populations in the Atlantic Ocean. Thus, the significant genetic diversity pool harboured by the Guafo Island population represents the northernmost point of expansion of this species from the Atlantic Ocean to the Pacific Ocean, which could be important for the eventual dispersal of the species to more northern areas of the Pacific and to the future adaptation of the species to changing environmental conditions on the Pacific coasts.