The evolution of density-dependent dispersal under limited information

Abstract

For an increasing number of species dispersal decisions have been shown to depend on local population density. This implies that organisms perceive – with sufficient accuracy – information about population density. However, research on the fitness value of such information, the adequate use of imprecise information, and how information use affects overall dispersal has only just started.A critical issue in such research necessarily concerns the adequate rule linking an individual's population density estimate to its readiness to emigrate; a spectrum of such rules has been proposed in the past. We use three prevalent rules and one rule specifically derived for situations of incomplete information to demonstrate that the adequacy of each rule strongly depends on the accuracy of information about population density: Simple bang–bang (threshold) behavior performs best if information is highly inaccurate, whereas a saturating response function (dispersal propensity gradually increasing with population density) out-competes all other strategies when individuals can estimate density accurately. The decision rule as well as the precision of information significantly influence average emigration probabilities establishing in metapopulations. Our results show that use of inadequate rules in models of dispersal evolution may lead to false dispersal decisions. Based on this analysis we present a rule that allows approximating an adequate dispersal response at the population level even when individuals possess incomplete information about local density. We conclude that individuals should generally invest little into the acquisition of (accurate) information even if such acquisition is associated with only small costs.