Preferential cannibalism as a key stabilizing mechanism of intraguild predation systems with trophic polymorphic predators

Theory predicts intraguild predation (IGP) to be unstable despite its
ubiquity in nature, prompting exploration of stabilizing mechanisms of
IGP. One of the many ways IGP manifests is through inducible trophic
polymorphisms in the intraguild (IG) predator, where a resource-eating
predator morph competes with the intraguild (IG) prey for the shared
resource while a top predator morph consumes the IG prey. Cannibalism is
common in this type of system due to the top predator morph’s
specialization on the trophic level below it, which includes the
resource-eating predator morph. Here, we explore the consequences of
inducible trophic polymorphisms in cannibal predators for IGP stability
using an IGP model with and without cannibalism. We employ linear
stability analysis and identify regions of coexistence based on the top
predator morph's preference for conspecifics vs. heterospecifics and
the IG prey's competitive ability relative to the resource-eating
morph. Our findings reveal preferential cannibalism (i.e. the preferential
consumption of conspecifics) stabilizes the system when the IG prey and
resource-eating morph have similar competitive abilities for the shared
resource. Though original IGP theory finds the IG prey must be a superior
resource competitor as a general criterion for coexistence, this is not
typically the case when the predator has an inducible trophic polymorphism
and the resource-eating morph is specialized in resource acquisition.
Preferential cannibalism may therefore be a key stabilizing mechanism in
IGP systems with a cannibalistic, trophic polymorphic IG predators,
providing further insight into what general mechanisms stabilize the
pervasive IGP interaction.