The Smell of Deceit: Record Number of Species Use Same Scent to Manipulate Each Other

What does deceit smell like? It turns out that it's the same smell for four different species. Scientists have found that four species at all different levels in the food chain use a single odor to communicate with and ruthlessly exploit each other.

Plant-feeding insects are often attracted to odors that are released by damaged plant tissue. This is because the damaged plants can be a good place to look for food, sexual partners or become egg-laying sites. For example, the jumping plant louse, called Diaphorina citri, hones in on the odor methyl salicylate, which is released by damaged young leaves of citrus trees. Yet other species have taken advantage of this.

The bacterium, Canditatus Liberibacter asiaticus infects citrus trees and hijacks its odor production. The bacterium then forces the tree to release methyl salicylate to mimic an attack by plant lice. The jumping plant lice, duped by the odor, fly toward the source. Yet they will not find enough food there and then will seek another tree-but only after the bacterium hitches a ride on their bodies. This allows the bacterium to infect new trees.

Yet the species that the scientists were interested in was the wasp, Tamarixia radiate. This insect lays its eggs on young jumping plant lice so that the wasp larvae can feed on them. The researchers wanted to find out whether the wasp is also attracted to the odor of methyl salicylate. In order to find out, they placed female wasps in an olfactometer, which is a Y-shaped device with each side emitting a different odor. The researchers found that the wasps were indeed attracted to methyl salicylate.

In fact, the wasps were more likely to find and attack young plant lice on plants infected with the bacterium, or on plants that had been treated with methyl salicylate. This showed that the wasp finds prey by "eavesdropping" on the odor signal exchanged.

"Communication between species is widespread in nature, but almost always involves only two or three species," said Lukasz Stelinski, one of the researchers, in a news release. "Here, we show for the first time that the same signal connects four different species, each at a different level in the food chain. Through their separate evolutionary histories, they independently hit on the use of methyl salicylate as a way to take advantage of their prey."

The findings are published in the journal Frontiers in Ecology and Evolution.