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

A recent genetic and biogeographical study of blue-eyed shags (Leucocarbo spp.) reveals rapid speciation in response to receding sea ice, resolving a long-standing paradox. The research, using time-calibrated phylogenetic analyses across 16 species and subspecies, shows that sub-Antarctic island lineages originated during the Pliocene or Early Pleistocene, contrasting with older lineages in South America and New Zealand. These findings suggest two major dispersal waves linked to interglacial cycles, with South America acting as a glacial refugium. The study highlights blue-eyed shags as a model system for understanding founder-event speciation and adaptation in Southern Ocean birds.

Rawlence, N. J., Salis, A. T., Spencer, H. G., Waters, Jonathan M., Scarsbrook, L., Mitchell, K. J., Phillips, R. A., Calderón, L., Cook, T. R., Bost, C.-A., Dutoit, L., King, Tania M., Masello, J. F., Nupen, L. J., Quillfeldt, P., Ratcliffe, N., Ryan, P. G., Till, C. E., & Kennedy, M. (2022). Rapid radiation of Southern Ocean shags in response to receding sea ice. Journal of Biogeography, 49(5), 942–953. Portico. https://doi.org/10.1111/jbi.14360