Divergent evolution of dispersal in a heterogeneous landscape

The evolution of dispersal is investigated in a landscape of many patches w ith fluctuating carrying capacities and spatial heterogeneity in temporal f luctuations. Although asynchronous temporal fluctuations select for dispers al, spatial heterogeneity in the distribution of fluctuating environmental variables selects against it. We find evolutionary branching in dispersal r ate leading to the evolutionarily stable coexistence of a high- and a low-d ispersal phenotype. We study how the opposing forces of selection for and a gainst dispersal change with the relative size and the environmental qualit ies of the source and sink habitats. Our results suggest that the evolution of dispersal dimorphism could be a first step towards speciation and local adaptation.