February 4, 2008

Insect Biodiversity Linked to Nutritional Preferences, Study Finds

COLLEGE STATION – New research suggests different species of plant-eating insects will consume only their fair share of food supplies in order to coexist.

“Some species practiced an Atkin’s diet, preferring protein over carbohydrates. Others practiced a Homer Simpson diet and ate more carbohydrates than protein,” said Dr. Spencer Behmer, a Texas AgriLife Research entomologist.

He said some insects preferred a more balanced diet of both protein and carbohydrates. “This research sheds new light on what influences species diversity and might help us better understand the factors we need to consider in terms of protecting and managing biodiversity,” Behmer said.

The findings were reported recently in the online edition of the Proceedings of the National Academy of Sciences, which can be found at http://www.pnas.org/ .

Behmer studied the eating habits of seven species of grasshoppers that fed on the same group of plants, he said. The various species ate food in different proportions to obtain protein and carbohydrates.

“What we’ve basically discovered is that one way insects can reduce the competition for shared resources is by ingesting different ratios of nutrients,” said Behmer, who co-authored the study with Dr. Anthony Joern of Kansas State University.

“So one insect species might eat a little bit of plant A, maybe a little bit more of plant B and some of C,” he said. “Another species might eat different proportions of these same foods. By eating the plants in different ratios, they can obtain a different balance of nutrients, and one that is best for that species.”

A mainstay of ecological theory and practice is that coexisting species use different resources, according to Behmer’s paper, which was posted Jan. 31. Most plant-eating insects feed on a narrow range of plants. Monarch butterfly caterpillars, for example, feed only on milkweeds. These insects are called “specialists.”

But some insects, such as the grasshopper, feed on a wide variety of plants, Behmer said. They’re called “generalists.” They, in effect, share their food to survive in the same area where their foraging overlaps.