Geographic dialects in volatile communication between sagebrush individuals.

Plants respond to volatile cues emitted by damaged neighbors to increase their defenses against herbivores. We examined whether plants communicated more effectively with local neighbors than distant neighbors in a reciprocal experiment at two sites. Three branches on focal plants were incubated with air from (1) a control, (2) an experimentally clipped "foreign" plant from 230 km away, or (3) an experimentally clipped "local" plant from the same population as the focal plant. Branches incubated with air from the controls experienced 50-80% more leaf damage than those receiving air from experimentally clipped plants. Of more interest, branches receiving volatiles from experimentally clipped "local" plants received 50-65% of the leaf damage as those receiving volatiles from experimentally clipped "foreign" plants. Sabinyl compounds and related terpinenes were found to differ consistently for plants from southern and northern sites. These results indicate that cues vary geographically in their effectiveness and suggest that sagebrush responds more strongly to local than foreign dialects.