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In response to climate change, two related species of Colias (sulphur) butterflies have adapted by broadening the range of their ideal feeding temperatures and also by shifting their optimal feeding temperature to a higher one. (Credit: Lisa Brown/Flickr)

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Caterpillars adapt to gobble food in the heat

Due to climate change over the last 40 years, some caterpillars have evolved to feed rapidly at higher temperatures, new research shows.

The findings suggest the caterpillars are evolving quickly to cope with a hotter, more variable climate. Scientists say the new work represents a rare instance of how recent climate change affects physiological traits, such as how the body regulates feeding behavior.

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“To our knowledge, this is the first instance where we show changes in physiological traits in response to recent climate change,” says Joel Kingsolver, distinguished professor of biology at the University of North Carolina at Chapel Hill.

Caterpillars can only eat and grow when it’s not too cold and not too hot, Kingsolver says. When temperatures are ideal, caterpillars eat with reckless abandon and can gain up to 20 percent of their body weight in an hour.

That growth determines their ability to survive, how quickly they become adult butterflies and their ultimate reproductive success.

For the new study, published in Functional Ecology, researchers compared modern caterpillars to their ancestors from 40 years ago.

Results show that two related species of Colias (sulphur) butterflies have adapted in two ways: they broadened the range of their ideal feeding temperatures and also shifted their optimal feeding temperature to a higher one.

Faster meal times

Researchers measured changes in climate at study sites in Colorado and California and then examined changes in how fast caterpillar ate using current and historical data from the 1970s, collected by Kingsolver’s graduate adviser Ward Watt.

Although they found little change in the average air temperature at both study sites, they noticed that the frequency of hot temperatures—that is, temperatures that exceeded 82 degrees Fahrenheit—increased two-fold in Colorado and four-fold in California over the past 40 years.

In response to these temperature fluctuations, modern caterpillars in Colorado ate faster at higher temperatures than their 1970s counterparts. In California, the modern caterpillars ate faster at both high and low temperatures than did their ancestors, but their optimal feeding temperatures didn’t  change.

“These two species of caterpillars adapted to the increased frequency of higher temperatures over 40 years in two different ways, but both are better suited than their ancestors to thrive in a hotter, more variable climate,” says Jessica Higgins, a graduate student in Kingsolver’s lab who spearheaded the study.

“Our climate is changing. The thermal physiology of these species is changing, too.”

Fellow graduate student Heidi MacLean and Lauren Buckley at the University of Washington contributed to the study.

Source: UNC-Chapel Hill

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