Absorptivity due to Climate Change Affects Wing Melanin in Butterflies

by Anna Alquitela

Climate change affects many organisms in varying ways. Organisms that are unlikely to migrate must adapt to climate change through evolutionary responses. Numerous studies have documented evolutionary responses to climate change over a period of one to three decades. However, the study by Kingsolver and Buckley (2015) provides evidence of a delayed evolutionary response to climate change for the subalpine and alpine butterfly, Colias meadii, in the southern Rocky Mountains of Colorado. Kingsolver and Buckley investigated the evolution of wing melanin of C. meadii and its effect on selection. They state that many species of the study area have adapted to their local climate conditions and “have limited potential for large-scale migration and gene flow.”

Comparing wing melanin to regional climate change, the authors relied on models to predict selection and evolutionary responses over the past 50–60 years. They also analyzed the changes in population mean fitness over time at the subalpine and alpine sites by relating solar absorptivity (the amount of radiation absorbed by the body) to fitness for a given site and year. Between 1955 and 2010, during the month of July, both the mean and daily maximum temperatures increased significantly for the study sites. Kingsolver and Buckley found that butterflies at the subalpine site had lower optimal absorptivity and a higher maximal fitness, whereas butterflies at the alpine site displayed a cohesive increase of optimal absorptivity and fitness, thus determining that the increased wing melanin exhibited in C. meadii has been favored at the alpine site. However, there are two opposing factors affecting fitness: increased melanin enables increased flight and reproduction, but it also increases thermal stress that negatively affects egg viability and adult survival rates. A premature evolutionary response to climate change would adversely affect the populations of C. meadii, therefore it would be expected that the butterflies that have survived to reproduce effectively are those that have a slower evolutionary response to climate change.

Kingsolver, J. G., Buckley, L. B. 2015. Climate variability slows evolutionary responses of Colias butterflies to recent climate change. Proceedings of the Royal Society of London B: Biological Sciences 282, 20142470.



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