Elephant seals (Mirounga leonina) at Potter Peninsula, King George Island, Antarctica: genetic variation of the breeding colony and gene flow with other colonies

Abstract

In this study, we describe, for the first time, the genetic composition of the southern elephant seal Mirounga leonina (SES) breeding colony at Potter Peninsula (PP) (King George Island, Antarctica) based on a fragment of mitochondrial DNA (mtDNA) D-loop. This colony is known for presenting the highest average weight of reproductive females, the highest mass recovery rate during the foraging trip between the reproductive and molting haulouts, and the highest average weight of pups at weaning. Samples were taken during the 2007 and 2008 breeding seasons from which 158 new mtDNA control region sequences (299 bps) were obtained, and 42 haplotypes were identified. We combined these data with previously published mtDNA control region datasets to explore the genetic relationships between the colony under study and other SES colonies. Out of the total PP haplotypes (n = 42), 35.7% corresponded to unique haplotypes and the rest were shared haplotypes. These latter ones were mainly shared with Falkland/ Malvinas and Elephant Island colonies. In the haplotype network analysis, the ancestral haplotypes of the species were related to Malvinas/Falklands and South Shetlands Islands. Therefore, PP would retain ancestral mitochondrial genes. The pairwise Fst values showed that, for the most part, all breeding colonies of SES examined herein differed significantly from each other. The exceptions were PP and Elephant Island (EI) which were significantly different from all other colonies but not between them. We propose Malvinas/Falkland as a glacial refuge for the South Shetland Islands SES breeding colonies during the last glacial maximum (LGM). Determining how a species is divided into stocks is crucial for the understanding of population dynamics; therefore, we believe that new studies on the PP colony, including biparental markers and a representative sampling of the South Georgia and Kerguelen Islands populations, are essential to better understand the SES population dynamics.