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Butterflies with smaller or lighter coloured wings most at risk from climate change, say University of Cambridge scientists

Butterflies with smaller or lighter coloured wings are likely to be at the greatest threat from climate change, ecologists at the University of Cambridge say.

The family, wing length and wing colour of tropical butterflies all influence their ability to withstand rising temperatures, they found.

Esme Ashe-Jepson conducing fieldwork in Panama, with a Juditha caucana butterfly from the Riodinidae family.Picture: Esme Ashe-Jepson
Esme Ashe-Jepson conducing fieldwork in Panama, with a Juditha caucana butterfly from the Riodinidae family.Picture: Esme Ashe-Jepson

The Lycaenidae family, which contains more than 6,000 species of butterflies - the majority of which live in the tropics - are believed to be particularly vulnerable.

While butterflies with larger or darker coloured wings could fare better as temperatures rise, they could still experience dramatic declines amid sudden heatwaves or if cool microclimates were lost through deforestation, they say.

Butterflies rely on the sun’s warmth to give them energy and use thermoregulation strategies to maintain a balanced body temperature against changing air temperatures.

This can include flying to a shady spot or angling wings away from the sun - thermal buffering. When this is not possible or temperatures become too hot, species rely on physiological mechanisms such as the production of heat shock proteins to withstand high temperatures - thermal tolerance.

Researchers measured the temperature of more than 1,000 butterflies in multiple habitats in Panama using tiny thermometer-like probes and compared it to the surrounding air or vegetation to measure their thermal buffering.

They then measured their ability to withstand extreme temperatures to assess their thermal tolerance.

Thermal buffering abilities were found to be stronger in darker-winged butterflies, who could also tolerate higher temperatures than paler-winged butterflies.

But those that were good at thermal buffering were not so strong at thermal tolerance and vice versa.

Lead author Esme Ashe-Jepson, a PhD student at the University of Cambridge’s Department of Zoology, said: “Butterflies with physical characteristics that may help them to avoid the sun’s heat, like having large wings that enable them to fly quickly into shade, rarely experience high temperatures, and so have not evolved to cope with them. On the other hand, species which can cope with higher temperatures physiologically have experienced less selective pressure to evolve heat-avoiding behaviours.

“As temperatures continue to rise, and forest fragments get smaller and further apart because of deforestation, butterflies which rely on their surroundings to avoid high temperatures may not be able to travel between forest fragments, or cope with increasingly common heatwaves.

“Ultimately all insects, including butterflies, the world over are likely to be affected by climate change.

“Adaptation to climate change is complex and can be impacted by other factors such as habitat destruction. We need to address these two global challenges together.”

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