An armyworm on a tomato plantDR. BRIAN CONNOLLYWhen plants come under attack—by a hungry caterpillar, for instance—many of them activate defenses that make their foliage less tasty, less nutritious, or toxic. But until now, scientists weren’t sure what the consequences of these plant defenses were for the caterpillar. In a paper published today (July 10) in Nature Ecology & Evolution, researchers have shown that a tomato (Solanum lycopersicum) plant’s protections can encourage beet armyworm caterpillars (Spodoptera exigua) to cannibalize other caterpillars.
“We’ve known for a long time that herbivores do eat other insects, but so far people studying herbivory have kind of ignored that because it’s a lot easier to put herbivores in a neat bin in which they only eat plants,” says Michigan State University ecologist William Wetzel, who did not participate in the study. “And this is some of the first work to really incorporate the effects of cannibalism into plant-herbivore interactions.”
John Orrock, an ecologist at the University of Wisconsin, Madison, usually studies how animals behave when they’re at risk of being attacked, but became intrigued by the ability plants have to also respond to threats. “Plants aren’t just bystanders,” he says.
One of plants’ reactions is to produce nasty-tasting chemicals, and Orrock ...
