The Brown Argus butterfly has changed its diet and spread north in response to climate change, according to scientists at the Department of Biology, University of York.

Research shows that the butterfly eats Wild Geranium plants to complete its life cycle.  Geraniums are plentiful across the UK countryside and the change in diet has led to the butterflies spreading northwards by approximately 79 kilometres.  The Brown Argus butterfly has now become common in the countryside of southern England, the press release states.

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.”

This is positive news for the species as back in the eighties it was considered scarce in Britain.  In the eighties the caterpillars would mainly be limited to Rockrose plants but has summer temperatures continue to soar, the caterpillars use the Wild Geraniums, which are more suitable for butterflies in warmer climes.

Co-author Richard Fox, from the charity 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.”

The research has been published in Science and was funded by the Natural Environment Research Council.  Scientists from the University of York, NERC Centre for Ecology & Hydrology and Butterfly Conservation were all involved in the study.

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