St Patrick's Day special: Irish frogs may have survived Ice Age

Irish frogs may have survived the Ice Age by retreating to a tiny ice-free refuge in Ireland, while mainland Britain’s frogs died out to be re-populated by European frogs, new research suggests.

Recent evidence has shown that Ireland's frogs differ from those of mainland Britain, shedding new light onto where frogs disappeared to when the Ice Age hit Europe over 10,000 years ago.

Research by scientists at the Zoological Society of London (ZSL) and Queen Mary, University of London suggests that some of the ancestors of Ireland's frogs survived the Ice Age, whereas those in the rest of the British mainland may have retreated, later to be re-populated by frogs from mainland Europe once the Ice Age was over.

The paper, in the journal Heredity, suggests that a small ice-free refuge may have existed in Ireland during the Ice Age, and here amphibians may have been able to see out the worst of the cold and ice.

Scientists found the genetic differences between Common Frogs (Rana temporaria) in mainland Britain and those of mainland Ireland while undertaking research into amphibian disease.

Lead author Dr Amber Teacher, from ZSL, said: "It appears that some frogs may have survived through the glaciations in this ice-free part of Ireland, as there is a distinct genetic lineage found in the South of Ireland that is not found elsewhere in Europe."

"So within Ireland, we can find frogs that originate from this small part of southern Ireland, mixed with the frogs that came from western Europe to repopulate the British Isles after the ice age retreated."

The work was undertaken with the help of the Irish Peatlands Conservation Council and Froglife, a UK wildlife charity for amphibians and reptiles.

"This study has given us a unique and fascinating window into the history of frogs in the British Isles." said Lucy Benyon, Froglife’s Wildlife Information Officer.

Article: Teacher, AGF, Garner, TWJ, Nichols, RA (2009) European phylogeography of the common frog (Rana temporaria): routes of postglacial colonization into the British Isles, and evidence for an Irish glacial refugium. Heredity. Advance online publication.