Proc. R. Soc. Lond. B doi:10.1098/rspb.2007.1153 (2007)

Alamy

Atlantic cod populations survived the last ice age on both North American and European coastlines, according to a recent study. The locations of Atlantic cod in the colder climate were predicted with models of the cod's ecological niches and then verified by genetic analyses. Similar ecological-niche modelling may help anticipate extinctions or shifts in species' ranges caused by global warming.

Grant R. Bigg of the University of Sheffield and a team of international colleagues tested two ecological-niche models against current distributions of cod and then used the models to map geographic ranges where cod should have lived during the last glacial maximum (LGM), about 21,000 years ago. To independently predict the historic ranges, the researchers examined sequence variations in certain cod genes. By measuring the likely rate of genetic change and the extent of sequence differences between present-day North American and European cod, they confirmed that the two groups diverged before the LGM and endured the ice age as separate populations.

The results support the disputed idea that parts of the Canadian coast were then free of glaciers, providing warmer refuges where hardy species such as cod could survive. Whether the fish's resilience is expected to see it through future climate regimes, however, remains to be studied.