The dynamics of the Schoener-Polis-Holt model of intraguild predation

(Communicated by Yang Kuang) ABSTRACT. Intraguild predation occurs when one species (the intraguild predator) pre-dates on and competes with another species (the intraguild prey). A classic model of this interaction was introduced by Gary Polis and Robert Holt building on a model of com-peting species by Thomas Schoener. A global analysis reveals that this model exhibits generically six dynamics: extinction of one or both species; coexistence about a globally stable equilibrium; contingent exclusion in which the first established species prevents the establishment of the other species; contingent coexistence in which coexistence or dis-placement of the intraguild prey depend on initial conditions; exclusion of the intraguild prey; and exclusion of the intraguild predator. Implications for biological control and com-munity ecology are discussed. 1. Introduction. Intraguild predation occurs when one species (the intraguild predator) preys on and competes for limiting resources with another species (the intraguild prey). This mixture of predation and competition is observed in a diversity of freshwater, marine, and terrestrial food webs [2, 3]. For example, in freshwater streams, bluegills and insect