THE SPECIFICITY OF EAVESDROPPING ON SAGEBRUSH BY OTHER PLANTS

Wild tobacco growing in a field near experimentally clipped sagebrush became more resistant to herbivores than tobacco plants near unclipped sagebrush. Here, we asked whether eavesdropping on sagebrush is a common phenomenon. Do three other forb species that grow near sagebrush experience less herbivory when their sagebrush neighbors are clipped experimentally? Similarly, we asked if sagebrush becomes more resistant when conspecific neighbors are clipped. We found that levels of damage to leaves of lomatium, lupine, and valerian were unaffected by experimental clipping of neighboring sagebrush. These three forbs share many generalist herbivores with sagebrush, as does wild tobacco. Sagebrush individuals near clipped neighbors experienced approximately half the leaf loss to herbivores over the summer as plants with unclipped neighbors. Most of this herbivory was caused by generalist grasshoppers and mammals. Success of a chrysomelid beetle that specializes on sagebrush was unaffected by clipping neighboring sagebrush. These results indicate that communication between sagebrush and tobacco is not a unique phenomenon since sagebrush also responded when neighbors were clipped. In contrast, other plant species generally respond less strongly to cues than does tobacco, indicating that not all species respond to relatively high levels of jasmonate in their environments. Eavesdropping may be restricted to those species, like tobacco, that are strongly inducible and to those species, like sagebrush, that release high concentrations of cues.