A butterfly has changed its diet and moved northwards in response to climate change, a study today reveals.
University of York researchers found that warmer summers have allowed the Brown Argus butterfly to complete its life cycle by eating wild Geranium plants.
Because the Geraniums are widespread in the UK, this change in diet has allowed the butterfly to rapidly expand its range.
Over the past 20 years, the Brown Argus has spread northwards by around 79 kilometres and has become common in the countryside in much of southern England.
Lead author PhD student Rachel Pateman, of the University of York's Department of Biology and the NERC Centre for Ecology & Hydrology, said: "Many species are shifting their distributions northwards as the climate warms, but this previously scarce species has surprised everyone by moving its range at over twice the average rate."
Co-author Chris Thomas, Professor of Conservation Biology at York, said: "Because wild Geraniums are widespread in the landscape, the butterflies can now move from one patch of host plants to next and hence move rapidly through the landscape - expanding their range generation after generation."
David Roy, from the NERC Centre for Ecology & Hydrology, added: "The change in diet represents a change to the interactions between species - in this case between a butterfly and the plants that its caterpillars eat - caused by climate warming.
"Changes to the interactions between species are often predicted to alter the rate at which species shift their distribution in response to climate change; and now we have demonstrated this in nature."
Richard Fox, from Butterfly Conservation, said: "It is important that we understand how and why species are responding to climate change.
"Such research would not be possible without the thousands of records of butterflies our dedicated volunteers have collected over many decades, which have allowed us to detect these long term changes."