Plant-emitted semi-volatiles shape the infochemical environment and herbivore resistance of heterospecific neighbors.

Plant-emitted volatiles have been reported to shape ecological interactions occurring among species within single or between multiple trophic levels. The ecological contribution of volatiles to plant-herbivore, plant-pathogen, plant-to-plant and multitrophic interactions can be mutualistic, or may either favour or disfavour the players involved in the infochemical network. Emitting, perceiving or being passively engaged with airborne volatiles can result in ecological costs and/or benefits, render competitive advantage and shape population dynamics. We recently demonstrated a cost-effective way for plants to take advantage of volatile-based defence: by adsorbing neighbor-emitted compounds to defend against herbivory. We found that specific semi-volatiles emitted by Rhododendron tomentosum Harmaja are adsorbed to neighboring birch (Betula sp.) foliage in a natural habitat, in a field set-up and in the laboratory. These semi-volatiles were found to deter certain birch herbivores, and may thus confer associational resistance to birch. Here we show the relative change in the volatile profile of birch that occurs when neighbored by R. tomentosum. We further discuss the potential wider role of biogenic semi-volatiles for ecological interactions in natural environments and suggest how they might be utilized for pest management in agricultural crop production.