Population structure and long-term decline in three species of heart urchins (Abatus spp.) in the Vestfold Hills, East Antarctica.

Understanding the patterns of population genetic structure in benthic species is essential to preserve marine diversity in Antarctica. Genetic structuring of populations can show signals of historic processes (such as refugial... [ view full abstract ]

Understanding the patterns of population genetic structure in benthic species is essential to preserve marine diversity in Antarctica. Genetic structuring of populations can show signals of historic processes (such as refugial populations in ice-free areas during Pleistocene glaciations), or microevolutionary processes (e.g. gene flow, selection, drift). In addition, potential impacts of human pollutants in wastewaters discharged to coastal waters adjacent to Antarctic stations can produce changes in the magnitude and distribution of genetic diversity (e.g. by selection of tolerant genotypes or diversity loss associated with increased mortality). We used seven microsatellite markers to examine genetic variation in populations of three sympatric Antarctic sea urchin species from the order Spatangoida (Abatus ingens, A. shackletoni and A. philippii), all with brooding life history strategies. Samples were collected from sites at varying distances from the outfall of wastewater discharge from Davis Station. We found genetic evidence of a long-term population decline in all three species, but the estimated timing at the decline precedes any anthropogenic activities. Two genetic clusters inferred in A. ingens and A. shackletoni suggest secondary contact after population differentiation in glacial refugia. Life history is not a good predictor of fine-scale population structure in these species, with gene flow possible at distances of 5km. There was no evidence for an effect of pollution from Davis Station on genetic variation, however, potential limitations to detect such an impact are discussed. The reduced effective population size observed for these Antarctic benthic species highlights their fragility and the need for conservation concern.