Ecological role of volatiles produced by plants in response to damage by herbivorous insects

Plants often release a blend of volatile organic compounds in response to damage by herbivorous insects that may serve as cues to locate those herbivores by natural enemies. The blend of compounds emitted by plants may be more variable than is generally assumed. The quantity and the composition of the blends may vary with the species of the herbivore, the plant species and genotype within species, the environmental conditions under which plants are grown, and the number of herbivore species attacking the plant. Although it is often assumed that induced emission of these compounds is an adaptive tactic on the part of plants, the evidence that such responses minimize fitness losses of plants remains sparse because the necessary data on plant fitness rarely have been collected. The application of techniques of evolutionary quantitative genetics may facilitate the testing of widely held hypotheses about the evolution of induced production of volatile compounds under natural conditions.