Consistent individual variation in plant communication: do plants have personalities?

Animal biologists have recently focused on individual variation in behavioral traits and have found that individuals of many species have personalities. These are defined as consistent intraspecific differences in behaviors that are repeatable across different situations and stable over time. When animals sense danger, some individuals will alert neighbors with alarm calls and both calling and responding vary consistently among individuals. Plants, including sagebrush, emit volatile cues when they are attacked by herbivores and neighbors perceive these cues and reduce their own damage. We experimentally transferred volatiles between pairs of sagebrush plants to evaluate whether individuals showed consistent variation in their effectiveness as emitters and as receivers of cues, measured in terms of reduced herbivore damage. We found that 64% of the variance in chewing damage to branches over the growing season was attributable to the identity of the individual receiving the cues. This variation could have been caused by inherent differences in the plants as well as by differences in the environments where they grew and their histories. We found that 5% of the variance in chewing damage was attributable to the identity of the emitter that provided the cue. This fraction of variation was statistically significant and could not be attributed to the environmental conditions of the receiver. Effective receivers were also relatively effective emitters, indicating consistency across different situations. Pairs of receivers and emitters that were effective communicators in 2018 were again relatively effective in 2019, indicating consistency over time. These results suggest that plants have repeatable individual personalities with respect to alarm calls.