Limited genetic differentiation among chinstrap penguin (Pygoscelis antarctica) colonies in the Scotia Arc and Western Antarctic Peninsula

Long-term monitoring of seabird numbers around Antarctica has revealed that the chinstrap penguin (Pygoscelis antarctica) is largely declining throughout its range in the Scotia Arc. Whether archipelagos across this large area remain connected via dispersal or represent genetically isolated groups has not yet been established. The purpose of this study was to assess the level of genetic differentiation between four breeding colonies on the Western Antarctic Peninsula (WAP), South Shetland, South Orkney, and South Sandwich Islands using microsatellite-based analysis of population structure. All colonies had similar levels of genetic diversity (mean heterozygosity, H O = 0.583) but colonies from the WAP and South Orkney Island had significant inbreeding coefficients. Hierarchical and pairwise F-statistics revealed very limited population structure in the Scotia Arc, with weak differentiation between colonies from the WAP, South Shetland and South Orkney Islands relative to the South Sandwich Islands, which are situated at least 1000 km apart from these other archipelagos. Bayesian model-based clustering methods found no evidence of significant population structuring, suggesting that whilst some isolation by distance may occur, there are no strong barriers to dispersal across this wide geographic range. No evidence of sex-biased dispersal was detected. We conclude that chinstrap penguin colonies across the Scotia Arc represent one interconnected breeding population. High levels of gene flow may be important in maintaining smaller, less stable colonies, and this status should be preserved by creating dispersal corridors throughout the Scotia Arc

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