Global dispersal reduces local diversity

Metapopulation models and stepping-stone models in genetics are based on ve ry different underlying dispersal structures, yet it can be difficult to di stinguish the behaviour of the two kinds of models. We demonstrate a striki ng qualitative difference in the equilibrium behaviour possible with these two kinds of dispersal. If, in a local patch, there are multiple stable equ ilibria (and consequently an unstable equilibrium), we demonstrate that, fo r the spatial system with a metapopulation structure, at equilibrium every patch has to be near one of the stable equilibria. This. contrasts with the clinal structure possible with a stepping-stone or continuous space model; thus the result can be used to deduce qualitative information about the fo rm of dispersal from observations of allele frequencies.