PARENT SESSION
Oral Session # 84: Trophic Structure II: Terrestrial and Aquatic Systems.
Presiding: MD Moran
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Meeting Room 202.
Incorporating predator phytophagy into intraguild predation theory.
Daugherty, Matt*,1, Briggs, Cherie1, 1 University of California-Berkeley, Berkeley, CA
ABSTRACT- Thus far, intraguild predation (IGP) theory has focused on small subunits of food webs, consisting of a top consumer, an intermediate consumer, and a shared resource. In many systems, IGP interactions occur in the context of a more complex food web, with multiple possible prey items for predators. Polyphagous predator populations are supplemented by feeding on prey outside of the IGP module. This is especially true for highly omnivorous predators, such as predatory heteroptera, who are involved in IGP with other predators, and also feed on multiple herbivores and plants. We investigated the effect of a trophic supplement, predator phytophagy, on a 3+ level IGP model that includes a plant, an herbivore, and two predators (IG prey and IG predator). Predator phytophagy affects the ability of the predators to persist along a productivity gradient and to suppress the herbivore population, and the effects are dependent on which predator is plant feeding. Phytophagous IG prey can invade at lower plant quality, persist at higher plant quality, and suppress herbivores better than non-phytophagous IG prey. A phytophagous IG predator invades at lower plant quality, it displaces the IG prey at lower plant quality, and it disrupts herbivore control more than a non-phytophagous IG predator. Thus, IG prey phytophagy increases the potential for predator coexistence and pest suppression, while IG predator phytophagy reduces coexistence and pest suppression. Yet, even small amounts of phytophagy tend to destabilize the dynamics, and extinction of one of the predators due to unstable dynamics is likely over much of parameter space.
Key words: trophic supplement, omnivory, productivity, coexistence