Evol Ecol Res 12: 151-168 (2010)     Full PDF if your library subscribes.

Intraguild predation and interspecific co-existence between predatory endotherms

Maano Aunapuu1,2, Lauri Oksanen3,4, Tarja Oksanen1 and Erkki Korpimäki3

1Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden, 2Jämtland County Administrative Board, Östersund, Sweden, 3Department of Biology, Section of Ecology, University of Turku, Turku, Finland and  4Department of Natural Sciences, Finnmark University College, Alta, Norway

Correspondence: L. Oksanen, Department of Biology, Section of Ecology, University of Turku, FI-20014 Turku, Finland.
e-mail: lauoks@utu.fi


Background: According to the current predominant view, intraguild predation leads to the replacement of intermediate predators from highly productive habitats, whereas top predators and intermediate predators can co-exist in habitats with intermediate primary productivity. These predictions are contradicted by the observed abundance of intermediate predators in productive environments. But the predictions are derived by modelling interactions in food chains where the top predator is primarily adapted to exploit intermediate predators but also has some capacity to exploit the resources of the intermediate predators. We call this ‘food chain omnivory’. In contrast, ‘genuine intraguild predation’ is the case where the two predators have shared tactics of resource acquisition, resulting in broadly overlapping prey preferences – that is, the interacting predators belong to the same guild as defined by Root (1967).

Questions: What are the effects of productivity on genuine intraguild predation? Do the predictions for food chain omnivory apply also to genuine intraguild predation?

Methods: We modelled genuine intraguild predation by using parameter values such that the intermediate predator and the basal prey were equally valuable to the top predator. We assumed that the basal prey was a herbivore, with a carrying capacity directly proportional to primary productivity and a habitat-specific intrinsic rate of population growth that increases asymptotically in response to increasing primary productivity.

Results: With the above premises, intermediate predators can prevail even in highly productive habitat. Also, a priority effect is possible. Predictable replacement of intermediate predators by top predators requires that intermediate predators are much easier to find than basal prey. Stable co-existence requires biologically implausible parameter values.

Conclusions: Genuine intraguild predation is a destabilizing force in food webs. The dynamics of genuine intraguild predation systems differ from those in food chain omnivory systems where the intermediate and top predators have different feeding tactics and, therefore, different prey preferences.

Keywords: co-existence, exclusion, food chain intraguild predation, omnivory,

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