PARENT SESSION
Contributed Oral Session 143: Predator - Prey Ecology: Intraguild Predation and Community Dynamics
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 522 A, Level 5, Palais des congrès de Montréal
Mixed competition-predation interactions: How changes in population size distribution structure ecological communities.
van de Wolfshaar, Karen*,1, de Roos, Andre1, Persson, Lennart2, 1 Institute for Biodiversity and Ecosystem Dynamics, Amsterdam, Netherlands2 Departement of Ecology and Environmental Science, Umea, Sweden
ABSTRACT- Unstructured models of intraguild predation, in which a top predator forages on both an intermediate consumer and a shared resource, predict that coexistence between top predator and intermediate consumer is most likely at intermediate productivities and that the intermediate consumer goes extinct at higher productivities due to predation from the top predator. The models neglect the fact that intraguild predation most often represents an instance of life history omnivory, where individuals shift diet during development. We study the interaction between a top predator and an intermediate consumer, using a physiologically structured population model. The individual life history of both species is characterized by food dependent growth and development. In addition the top predator exhibits life history omnivory, competing with the intermediate consumer when small. When growing larger, the top predator switches to a mixed diet of alternative resource, conspecific and intermediate consumer prey. Along a productivity gradient in resource productivity we find that stable coexistence between top predator and intermediate consumer is generally not to be expected. Most commonly we find alternative stable equilibria with either the top predator or the intermediate consumer present. The presence of an intermediate consumer population may, however, induce a shift in size structure of the predator population to a more wide-spread size distribution. With the more wide-spread size distribution of the predator the predation pressure on small consumers is released, allowing coexistence of predator and consumer under conditions that an equilibrium with only top predators is stable as well. Coexistence of intermediate consumer and top predator may thus be promoted by size dependent processes.
Key words: life history omnivory, community structure, predator-prey interactions, size-structured model