Michael Singer / Wesleyan University A tiger swallowtail (Papilio glaucus) caterpillar feeds on black cherry (Prunus serotina), which was the only plant consumed by this species at the research field site. Download image

Caterpillars that eat multiple plant species are more susceptible to hungry birds

Dietary choices are evolutionary expression of risk vs. reward, UCI-Wesleyan study finds

Irvine, Calif., June 16, 2014 — For caterpillars, having a well-rounded diet can be fraught with peril.

UC Irvine and Wesleyan University biologists have learned that caterpillars that feed on one or two plant species are better able to hide from predatory birds than caterpillars that consume a wide variety of plants.

This is probably because the color patterns and hiding behaviors of the caterpillar “specialists” have evolved to allow them to blend into the background flora more effectively than caterpillars that eat many different plant species. Moving among these diverse plant types, the nonspecialists are not as camouflaged, making them easier for hungry birds to spot.

“It’s a classic example of risk vs. reward,” said Kailen Mooney, associate professor of ecology & evolutionary biology at UC Irvine. “Evolutionarily speaking, a caterpillar must choose between having a broad array of plants to feed upon but facing increased risk of being nabbed by a bird” and having a very limited menu but being less exposed to predators.

Mooney and Michael Singer, associate professor of biology at Wesleyan, led the study, which appears in the early online edition of Proceedings of the National Academy of Sciences this week.

Furthermore, the researchers found that all of this matters a lot to the plants. A species consumed by caterpillars more vulnerable to birds (those with varied diets) benefits from birds removing those caterpillars. In contrast, a plant species fed upon by caterpillars better able to hide from birds (those with highly restricted diets) doesn’t benefit as much from birds and must instead defend itself.

Mooney noted that this insight into the secret lives of caterpillars reveals not only the processes driving the evolution of insect diets but also the broad significance of caterpillar feeding for associated plants and birds.

Isaac Lichter-Marck and Timothy Farkas of Wesleyan, Eric Aaron of Vassar College and Kenneth Whitney of the University of New Mexico contributed to the study, which received support from the National Science Foundation (grants 1146203, 1257965, 1120794 and 0919178).

About the University of California, Irvine: Located in coastal Orange County, near a thriving high-tech hub in one of the nation’s safest cities, UC Irvine was founded in 1965. One of only 62 members of the Association of American Universities, it’s ranked first among U.S. universities under 50 years old by the London-based Times Higher Education. The campus has produced three Nobel laureates and is known for its academic achievement, premier research, innovation and anteater mascot. Led by Chancellor Michael Drake since 2005, UC Irvine has more than 28,000 students and offers 192 degree programs. It’s Orange County’s second-largest employer, contributing $4.3 billion annually to the local economy.

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