Inter-Guild Influences on Intra-Guild Predation in Plant-Feeding Omnivores

Abstract

Omnivorous predators that also feed on plants (omnivores) are important natural enemies of pest herbivores in many biological control programs. Bottom-up influences of the plant on the biology of these omnivores have been shown to have considerable influence on their interactions with target prey species. Likewise, plants should affect how these omnivores interact with other members of the natural enemy guild in biological control settings. Using community models, we show that intra-guild predation (IGP) by omnivores, in contrast to “pure predators” that do not feed on plants, could be affected by plant quality, and plant toxins. These models suggest that plants should affect IGP by omnivores in two ways: in the short-term by affecting the tendency of omnivores to engage in IGP, and in the long-term, by affecting both herbivore and omnivore population dynamics. We review the available literature effects of plant traits (plant quality, plant toxins, plant hairs, and plant kairomones) on IGP in omnivorous and pure predator species. Although plant traits do affect the nature and intensity of IGP by omnivores, we conclude that the effects are idiosyncratic, and are specific to the species involved.