Intense or Spatially Heterogeneous Predation Can Select against Prey Dispersal

Frederic Barraquand,David J Murrell,Filippo Castiglione

doi:10.1371/journal.pone.0028924

Abstract

Dispersal theory generally predicts kin competition, inbreeding, and temporal variation in habitat quality should select for dispersal, whereas spatial variation in habitat quality should select against dispersal. The effect of predation on the evolution of dispersal is currently not well-known: because predation can be variable in both space and time, it is not clear whether or when predation will promote dispersal within prey. Moreover, the evolution of prey dispersal affects strongly the encounter rate of predator and prey individuals, which greatly determines the ecological dynamics, and in turn changes the selection pressures for prey dispersal, in an eco-evolutionary feedback loop. When taken all together the effect of predation on prey dispersal is rather difficult to predict. We analyze a spatially explicit, individual-based predator-prey model and its mathematical approximation to investigate the evolution of prey dispersal. Competition and predation depend on local, rather than landscape-scale densities, and the spatial pattern of predation corresponds well to that of predators using restricted home ranges (e.g. central-place foragers). Analyses show the balance between the level of competition and predation pressure an individual is expected to experience determines whether prey should disperse or stay close to their parents and siblings, and more predation selects for less prey dispersal. Predators with smaller home ranges also select for less prey dispersal; more prey dispersal is favoured if predators have large home ranges, are very mobile, and/or are evenly distributed across the landscape.

Highlights

Dispersal is the glue which holds local populations together, enabling the re-colonisation of patches after local extinction, and maintaining gene flow between populations
Temporal variation in habitat quality can be driven by abiotic factors, but many biotic demographic factors contribute to temporal variability, such as chaotic population dynamics [5], or demographic stochasticity [6], and these can select for dispersal [7]
We show that the results are not sensitive to the dimensionality of space (1 or 2), and most importantly, that when predators reproduce according to prey density, the same selective pressures for dispersal are observed: more predation selects, all other things being equal, for less dispersive prey individuals

Summary

Introduction

Dispersal is the glue which holds local populations together, enabling the re-colonisation of patches after local extinction, and maintaining gene flow between populations. Temporal variation in habitat quality usually selects for increased/longer dispersal because a good location now is likely to decline in quality. Temporal variation in habitat quality can be driven by abiotic factors (e.g. climate), but many biotic demographic factors contribute to temporal variability, such as chaotic population dynamics [5], or demographic stochasticity [6], and these can select for dispersal [7]. Spatial variability in habitat quality is normally thought to select against dispersal because individuals strive to stay in high quality patches [8,9,10]. Travis [11] found that increased spatial autocorrelation of environmental variation tends to select for greater dispersal, and increased temporal correlation for a decrease in dispersal. When habitat quality is fine-grained, increased spatial autocorrelation in habitat quality may select for a decrease in dispersal distance [13]

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Results

Conclusion