On the evolution of density dependent dispersal in a spatially structured population model.

A simple metapopulation lattice model of two competing phenotypes is presented, where one phenotype reacts more sensitively to overcrowding by migrating to neighbouring local habitats. The sensitivity is formulated by means of a threshold density of the subpopulations, above which dispersal is triggered off. If this threshold density is not very far from the local carrying capacity, an increased mobility provides benefits on the metapopulation level. At a surprisingly small difference between migrational triggering thresholds, the phenotype of larger mobility (or lower threshold) squeezes out the less mobile one from the whole system in a wide parameter range. Evolutionary considerations give an optimal threshold level for our model metapopulation.