Indirect Interaction Webs: Herbivore-Induced Effects Through Trait Change in Plants

Although predation has a lethal effect on prey, mature terrestrial plants are rarely killed by herbivores, but herbivory can change plant allelochemistry, cell structure and growth, physiology, morphology, and phenology. This review explores the herbivore-induced indirect effects mediated by such plant responses following herbivory in terrestrial systems. Herbivore-induced indirect effects are ubiquitous in many plant–herbivore systems, and indirect interactions occur among temporally separated, spatially separated, and taxonomically distinct herbivore species. Unlike interspecific competition, herbivores can benefit each other through plant-mediated indirect effects. Herbivore-induced changes in plants occur at low levels of herbivory, which increases the likelihood of plant-mediated indirect interactions between herbivores. The herbivore-induced indirect effects result in interaction linkages, which alter species richness and abundance in arthropod communities. Such interaction linkages should be depicted using indirect interaction webs, which incorporate nontrophic, indirect links. The idea of interaction linkages by herbivore-induced indirect effects that shape community organization and biodiversity is an important revision of the traditional view of plant-based terrestrial food webs.