The evolution of dispersal distance in spatially-structured populations

Most evolutionary models of dispersal have concentrated on dispersal rate, with emigration being either global or restricted to nearest neighbours. Yet most organisms fall into an intermediate region where most dispersal is local but there is a wide range of dispersal distances. We use an individual-based model with 2500 patches each with identical local dynamics and show that the dispersal distance is under selection pressure. The dispersal distance that evolves is critically dependent on the ecological dynamics. When the cost of dispersal increases linearly with distance, selection is for short-distance dispersal under stable and damped local dynamics but longer distance dispersal is favoured as local dynamics become more complex. For the cases of stable, damped and periodic patch dynamics global patch synchrony occurs even with very short-distance dispersal. Increasing the scale of dispersal for chaotic local dynamics increases the scale of synchrony but global synchrony does not neccesarily occur. We discuss these results in the light of other possible causes of dispersal and argue for the importance of incorporating non-equilibrium population dynamics into evolutionary models of dispersal distance.