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Climate change works for the brown argus butterfly

Brown argus butterfly.
[Image courtesy of Louise Mair]

A pretty brown butterfly with orange spots on its wings, called the brown argus butterfly, is thriving in the United Kingdom for an interesting reason. Summers have become warmer in the last twenty years, and this change opens up new possibilities for where the butterfly can lay its eggs.

That's the conclusion of a study by Rachel Patemen of the University of York and the Natural Environment Research Council in the United Kingdom and colleagues. The research appears in the 25 May 2012 issue of the journal Science.

The brown argus was scarce in the 1980s but has since spread northwards in Great Britain at an unusually fast pace. In the past, the butterfly mainly used Helianthemum nummularium, or rockrose, as the host plant for its eggs.

Dr. Pateman's team analyzed data collected by British volunteers over the past four decades, describing sightings of the brown argus on various host plants.

The researchers found that the brown argus is increasingly using plants in the Geraniaceae family, primarily a plant called dove's-foot cranesbill, as hosts. And, this increase has taken place during relatively warm summers.

In the past, the butterflies preferred rockrose because these plants grow on south-facing slopes, which receive enough sun to make the plant hospitable to the brown argus. Warmer summers, however, have meant that the butterfly doesn't need to be so choosy and can branch out onto other host plants.

In their study, the authors note that just because warmer summers seem to be good for the brown argus, that doesn't mean that all species will have an easy time adapting to climate change.