For closely related kin, they snipped stem cuttings (clones), potted them, and then returned the pots to the field. They determined relatedness “by using microsatellites that varied among individual sagebrush clones.”

The result: “Plants responded more effectively to volatile cues from close relatives than from distant relatives in all four experiments and communication reduced levels of leaf damage experienced over the three growing seasons,” they wrote. “This result was unlikely to be caused by volatiles repelling or poisoning insect herbivores.”

Karban, who has studied plant communication among the sagebrush at the site since 1999, likened the plant communication to neighbors “eavesdropping.” They “hear” the volatile cues of their neighbors as predators damage them.

Plants do communicate, Karban said. A basic form of plant communication occurs when it is being shaded and it responds by moving away. “Some definitions of communication require that both the sender and receiver benefit by engaging in the behavior,” the researchers wrote. “Sagebrush is a long-lived perennial, making estimates of the costs and benefits of communication difficult although plants that responded to volatile cues from damaged neighbors experienced greater survival at the seedling stage and greater production of new branches and inflorescences over 12 years.”

Karban said that the volatiles released by “experimentally damaged plants are highly variable among individuals.”

“In the future we plan to examine this chemical variability to determine which chemicals are active as signals and why they exhibit so much variability,” Karban said. “Ultimately, we would like to be able to understand the chemical nature of the volatile cues, how plants use them to communicate, and whether as agriculturalists, we can control host plant resistance to herbivores.”

The work was supported by grants from the Japan Society for the Promotion of Science (JSPS) and the U.S. Department of Agriculture.

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