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<em>Science</em>: Once-Rare Butterfly Is Benefiting From Climate Change

The brown argus butterfly has expanded its range in the last 20 years, researchers report, as warmer conditions have turned seldom-used host plants into better places to lay eggs.

It’s often thought that one species’ dependence on others will limit its ability to relocate in response to climate change. But the new study, which appears in the 25 May issue of Science, shows that the opposite can also happen.

Rachel Pateman of the University of York and the Natural Environment Research Council in the United Kingdom and colleagues analyzed data collected by British volunteers over the past four decades, describing sightings of the brown argus on various host plants.

Historically, this pretty, orange and brown butterfly primarily has used Helianthemum nummularium, or rockrose, as the host for its eggs. Once hatched, the caterpillars eat the plant’s leaves. The brown argus was scarce in the 1980s but has since spread northwards at an unusually fast pace.


Brown argus butterfly | Image courtesy of Louise Mair


The new results show that the brown argus increasingly is using plants in the Geraniaceae family, primarily dove’s-foot cranesbill, as hosts. This increase has taken place during relatively warm summers.


In the past, rockrose was the preferred host in part because it grows 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.

“This study has highlighted that species do not respond to climate change in isolation,” Pateman said, “and that climate change affects how species interact with one another.

“In the case of the brown argus butterfly, changes in interactions with its food plants have helped it to respond to climate change very rapidly. However, changes to interactions may hinder other species, potentially putting them at risk of extinction.”


Read the abstract for “Temperature-Dependent Alterations in Host Use Drive Rapid Range Expansion in a Butterfly,” by Rachel Pateman and colleagues.