The stabilizing and destabilizing effects of cannibalism in an intraguild predation system

Intraguild predation (IGP), an interaction in which the intraguild (IG) predator competes with its intraguild (IG) prey for a shared resource, is ubiquitous in nature despite original theory predicting limited coexistence. A proposed stabilizing mechanism is cannibalism in the IG predator through its regulation of the predator population, which decreases predation pressure on the IG prey. We add cannibalism to an IG predator and include a cannibalism preference parameter to explore how the predator's preference for IG prey vs. conspecifics affects dynamics. We perform linear stability analyses. Our results show that strong cannibalism preference in the IG predator can 1) stabilize unstable IGP systems or 2) destabilize already-stable IGP systems depending on prey competitive ability. When the prey is a superior competitor, keeping with the assumption of original IGP theory, strong cannibalism preference drives the predator extinct. When the predator is a similar competitor for the resource as the prey, a common occurrence in natural IGP systems, preference for conspecifics over heterospecifics stabilizes this otherwise unstable system where the prey goes extinct. These results suggest that cannibalism preference, by altering the relative strengths of competition vs. predation between the predator and prey, determines the long-term stability of an IGP system.