Caterpillars Adapting to Climate Change
In Colorado and California, two species of caterpillars have
evolved to feed quickly at higher temperatures and at a wider range of
temperatures over the past 40 years, suggesting that they are evolving rapidly
to survive a hotter, more variable climate.
Joel Kingsolver at UNC-Chapel Hill began work that
represents an unusual instance of how recent climate change affects
physiological traits, such as how the body regulates feeding behavior. Jessica
Higgins, a graduate student in Kingsolver's lab led the study, working with
fellow graduate student Heidi MacLean, Lauren Buckley, and Kingsolver to
compare modern caterpillars to their ancestors from 40 years ago.
Kingsolver said that this is so far the first instance that
has shown changes in physiological traits in response to climate change. He
also explains that Caterpillars can eat and grow only when it's not too cold
and not too hot, but when temperatures are so ideal, caterpillars eat in unrestrained
manner 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 eventual reproductive success.
Results show that the two related species of Colias
(sulphur) butterflies have adapted in two ways. First, they extended the range
of their ideal feeding temperatures. Second, they shifted their optimal feeding
temperature to one that is higher.
The researchers measured changes in climate at the two study
sites and then examined changes in how fast caterpillars ate using current and
historical data from the 1970s. Even though little change in the average air temperature
at both study sites was discovered, it was noticed that the frequency of hot
temperatures (exceed 82 degrees Fahrenheit) increased two-fold in Colorado and
four-fold in California over the past 40 years. In response to these
temperature fluctuations, today’s 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, but their optimal
feeding temperatures did not change.
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