Gene flow on the ice: genetic differentiation among Adelie penguin colonies around Antarctica

Each summer Adelie penguins breed in large disjunct colonies on ice-free ar eas around the Antarctic continent. Comprising > 10 million birds, this spe cies represents a dominant feature of the Antarctic ecosystem. The patchy d istribution within a large geographical range, natal philopatry and a proba ble history of refugia, suggest that this species is likely to exhibit sign ificant genetic differentiation within and among colonies. We present data from seven microsatellite DNA loci for 442 individuals from 13 locations ar ound the Antarctic continent. With the exception of one locus, there was no significant genic or genotypic heterogeneity across populations. Pairwise F-ST values were low with no value > 0.02. When all colonies were compared in a single analysis, the overall F-ST value was 0.0007. Moreover, assignme nt tests were relatively ineffective at correctly placing individuals into their respective collection sites. These data reveal a lack of genetic diff erentiation between Adelie penguin colonies around the Antarctic continent, despite substantial levels of genetic variation. We consider this homogene ity in terms of the dispersal of individuals among colonies and the size of breeding groups and discuss our results in terms of the glacial history of Antarctica.