Evol Ecol Res 17: 815-834 (2016)     Full PDF if your library subscribes.

Competitive tragedies, habitat selection, and extinction (or not?)

Douglas W. Morris, Joshua G. Cronmiller and Erika Garcez Da Rocha

Department of Biology, Lakehead University, Thunder Bay, Ontario, Canada

Correspondence: D.W. Morris, Department of Biology, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario P7B 5E1, Canada. email: douglas.morris@lakeheadu.ca


Background: Increasing competitive ability of individuals can create a Tragedy of the Commons ending in extinction. Theory has not yet evaluated what role adaptive habitat selection might play in the tragedy and its outcome.

Methods: We used modified Ricker population models to simulate the long-term population dynamics emerging from a pure strategy of despotic habitat choice versus a mixed strategy of despotic and ideal-free habitat selection. Density in the better of two habitats was reduced by the threat of dominance in the pure strategy. Habitat selection switched to an ideal-free distribution at low densities in the mixed strategy. We used patterns of density and dispersal, giving-up densities, personalities and condition of meadow voles to search for the predicted switch in habitat selection.

Results: Extinction probabilities in simulated stochastic environments were always higher for pure than for mixed strategies. Experiments on meadow voles were only partially consistent with a density-dependent transition from ideal-free to despotic habitat selection. Densities and giving-up densities of voles in adjacent habitats were nearly identical when resources were equal and population size was small. Giving-up densities diverged dramatically when supplemental food was added to one habitat and not to the other. Despite biased dispersal from high- to low-quality habitat, there was no associated difference in population density, personality or body condition.

Conclusions: Pure habitat selection based on dominance places populations at greater risk of extinction than does a mixed strategy in which dominance disappears at low population sizes. Experiments on meadow voles yielded limited but nevertheless tantalizing support for such a density-dependent switch in habitat selection.

Keywords: adaptation, extinction, foraging behaviour, habitat selection, Microtus pennsylvanicus, patch use, Tragedy of the Commons.

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