Fig. 1.

Proposed ecological mechanisms by which dispersal can homogenize a metacommunity. a Dispersal homogenizes a metacommunity indirectly, by weakening selection across habitats via transfer of material, and only after selection is weakened. In this case, the critical dispersal rate required for homogenization (D_c) is high. b Dispersal homogenizes a metacommunity directly via immigration of individuals and the metacommunity is homogenized before selection is weakened. In this case, D_c is lower than in scenario A and depends on the ratio between growth and immigration of individuals. In both scenarios, D_c will depend on how strongly selection and dispersal are coupled