Genetic diversity and kinship relationships in one of the largest South American fur seal (Arctocephalus australis) populations of the Pacific Ocean

The genetic diversity of populations is the basis for individual fitness and potential adaptability to environmental changes. The South American fur seal (Arctocephalus australis) is a pinniped species that is widely distributed along the southern cone of South America. However, two distinct populations have evolved: the Northern Pacific/Peruvian population and the Southern Pacific/Atlantic population. One of the main breeding colonies of the Southern Pacific/Atlantic population is located on Guafo Island, in southern Chilean Patagonia. This breeding colony represents the closest reproductive population to the remote Peruvian group. Therefore, our study aimed to determine whether the Guafo colony may potentially facilitate gene flow, contribute new alleles, and increase genetic variability of the Peruvian populations, thereby linking the Northern and Southern Pacific populations for the species. In this study, species-specific microsatellite markers were developed to genetically characterize Guafo Island's South American fur seal population. Our results confirm that the Guafo colony is a panmictic population with evidence of lack of genetic structure. Further, our results indicate that most individuals are unrelated and that half-siblings are rare, suggesting that polygyny in this species is less frequent than previously thought. Finally, based on the identification of multiple pairs of full siblings, we also present the first genetic evidence of twins in South American fur seals. These attributes suggest that the Guafo colony is a large, panmictic population, which could act as a potential genetic reservoir, and ultimately assist in linking two genetically distinct populations.