Rapid radiation of Southern Ocean shags in response to receding sea ice

Understanding how natural populations respond to climatic shifts is a fundamental goal of biological research in a fast-changing world. The Southern Ocean represents a fascinating system for assessing large-scale climate-driven biological change, as it contains extremely isolated island groups within a predominantly westerly, circumpolar wind and current system. Blue-eyed shags represent a paradoxical seabird radiation—a circumpolar distribution implies strong dispersal capacity yet their species-rich nature suggests local adaptation and isolation. Here we attempt to resolve this paradox in light of the history of repeated cycles of climate change in the Southern Ocean.