PARENT SESSION
Thursday, August 10, 8:00-11:30 am
COS 85 - Predator-prey interactions
L-11, Lobby Level, Cook Convention Center
Presiders: J Laundre
Indirect interactions in stage-structured predator-prey systems: cannibalism, trait-mediated interaction, and trophic cascades.
Rudolf, Volker*,1, 1 University of Virginia, Charlottesville, VA
ABSTRACT- Cannibalistic and asymmetrical behavioral interactions between stages are common within size-structured predator populations. Using field experiments I highlight how such direct interactions between predator stages can result in density- and trait-mediated indirect interactions between a predator and its prey (DMII and ,TMII). Then I explore how such indirect interactions affect the outcome of predation and the effect of enrichment. A structured predator-prey model of the separate and combined effects of cannibalism and asymmetric-behavioral interactions between predator cohorts under different ecological scenarios shows that both cannibalism and intraspecific behavioral interactions can result in short- and long-term positive indirect connections between predator stages and the prey, including apparent mutualism. These positive interactions alter the strength of trophic cascades because the system dynamics are determined by the interaction between bottom-up and down-down effects. Contrary to the expectation of simpler unstructured models, enrichment increases both predator and prey abundance in systems with cannibalism or asymmetrical-behavioral interactions. Behavioral interactions between different stages of a predator reduce the short-term positive effect of cannibalism, but can enhance its positive long-term effects. Cannibalism and asymmetrical behavioral interaction between stages of a predator can also increase the abundance of the predator, even if the energy gain from cannibalism is less than one. Both interaction types reduce the destabilizing effect of enrichment. These results suggest that inconsistencies between data and simple models can be resolved by accounting for size-structured interactions within and among species.
Key words: Predator-prey interactions, Food web dynamics, Functional response