Evol Ecol Res 13: 495-511 (2011)     Full PDF if your library subscribes.

Switching strategies, population dynamics, and mechanisms of co-existence in food webs with Jekyll-and-Hyde species

Paul A. Orlando1, Joel S. Brown1, Howard E. Buhse, Jr.1 and Christopher J. Whelan2

1Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, USA and  2Illinois Natural History, c/o University of Illinois at Chicago, Chicago, Illinois, USA

Correspondence: P.A. Orlando, Department of Biological Sciences, University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL 60607, USA.
e-mail: porlan1@uic.edu


Definition: Intra-guild predators prey on members of other species that belong to the same guild.

Question: What are the effects of polymorphic intra-guild predators on population dynamics and diversity?

Mathematical method: We use differential equations to model a specific form of trophic polymorphism where the polymorphic species is an intra-guild predator. This species can switch between two morphs – Jekyll, which competes with the intra-guild prey for a shared resource, and Hyde, which preys on the intra-guild prey. For generality, we explore two different food web arrangements (with and without cannibalism of Hyde on Jekyll) and two different switching strategies (constant and variable).

Key assumptions: We assume that switching between the morphs occurs continuously and in both directions. We also assume that switching is cost-free.

Conclusions: Switching in general stabilizes population dynamics, except in the case of the cannibalistic food web with variable switching. Population subsidies from one morph to the other create ecological opportunity for a specialist species with identical ecology as the subsidizing morph. Switching enhances opportunities for co-existence with the intra-guild prey when Hyde subsidizes Jekyll. However, when Jekyll subsidizes Hyde, opportunities for co-existence with the intra-guild prey are diminished.

Keywords: intra-guild predation, mechanism of co-existence, phenotypic switching, trophic polymorphism.

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