Practice question

Associational resistance occurs when a plant suffers less herbivory because of the identity, abundance, or arrangement of neighboring plants. An unpalatable or chemically defended neighbor may mask host odors, visually conceal the focal plant, repel herbivores, reduce landing probability, or support predators and parasitoids that attack herbivores. The protected plant need not possess the neighbor’s defensive compound; reduced damage emerges from community context. This differs from chemical defense produced by the focal plant itself and from camouflage based solely on matching an abiotic background. It is also not necessarily mimicry, because the focal plant need not evolve resemblance to the unpalatable species. Associational effects can reverse: a highly attractive neighbor may concentrate herbivores and produce associational susceptibility, or a shared herbivore may spill over between hosts. Experiments test the mechanism by manipulating neighborhood composition while controlling focal plant density and measuring herbivore arrival or damage. The concept therefore demonstrates that plant resistance is partly an emergent property of local vegetation, not only an intrinsic trait of individual plants.