Genetic diversity in clustered colonies of an Antarctic marine mesopredator: a role for habitat quality?

Genetic structure may be highly variable across seabird species, and particularly among thosethat are distributed over large geographical areas. The Adélie penguin (Pygoscelis adeliae) is anumerically dominant Antarctic seabird that is considered to be a key species in coastal ecosystems.Since the Last Glacial Maximum, penguin colonization of the Antarctic coastline occurred at varyinggeographical and temporal scales, contributing to an incomplete understanding of how moderncolonies relate to each other at local or regional scales. We assessed the population genetic structureof Adélie penguins (n = 86 individuals) from three adjacent colonies along the Victoria Land coastusing molecular genetic markers (i.e. seven microsatellite loci isolated through next-generationsequencing). Our results indicate meta-population dynamics and possibly relationships with habitatquality. A generally low genetic diversity (Nei's index: 0.322-0.667) was observed within each colony,in contrast to significant genetic heterogeneity among colonies (pairwise FST = 0.071-0.148),indicating that populations were genetically structured. Accordingly, an assignment test correctlyplaced individuals within the respective colonies from which they were sampled. The presence of intercolonygenetic differentiation contrasts with previous studies on this species that showed a lack ofgenetic structure, possibly due to higher juvenile or adult dispersal. Our sampled colonies were notpanmictic and suggest a lower migration rate, which may reflect relatively stable environmentalconditions in the Ross Sea compared to other regions of Antarctica, where the ocean climate is warming.