In a surprising revelation, new research suggests that climate change may lead to a reduction in the distinctive spots of female Meadow Brown butterflies. The study, conducted by Professor Richard French-Constant from the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall, challenges long-held assumptions about the reasons behind variations in butterfly spots.
According to the findings, female Meadow Browns raised in warmer environments, specifically at 15°C, displayed fewer spots compared to those raised at 11°C. Those developed at 15°C had an average of just three spots, while their counterparts from cooler conditions had an average of six.
Professor French-Constant explains, “Our findings show that fewer of these hindwing spots appear when females experience higher temperatures during their pupal stage. This suggests the butterflies adapt their camouflage based on the conditions, making them potentially harder to spot on dry, brown grass common in hot weather.”
The study challenges the traditional understanding of Meadow Brown butterfly eyespot variation, which was previously attributed to genetic polymorphism. The new research reveals that the variation is caused by thermal plasticity, the ability to respond to changing temperatures.
While the effect on males is less pronounced, the study suggests that females, who usually develop larger hindwing spots, undergo this change for better camouflage in warmer climates rather than for sexual selection.
Professor French-Constant, whose father collected butterflies for biologist EB Ford, emphasized the unexpected consequence of climate change, stating, “This is an unexpected consequence of climate change. We tend to think about species moving north, rather than changing appearance.”
The researchers predict a continuous decrease in spotting among Meadow Browns as the climate warms. The study, published in the journal Ecology and Evolution, titled “Eyespot variation and field temperature in the Meadow Brown butterfly,” draws on current Cornish populations and historical collections from Eton and Buckingham.