Figure 1.

Mean fitness in the whole metapopulation (a) and in demes under weaker (b) and stronger selection (c), as a function of α (the proportion of demes under weaker selection), for different values of the migration rate m: 0.002 (filled squares, solid line), 0.01 (filled circle, dashed line), 0.05 (empty squares, dashed-dotted line), 0.1 (empty circles, dashed-double-dotted line), 0.5 (diamonds, dotted line). Other parameters are: number of demes n=100, deme size N=500, mutation rate per chromosome U=1, selection coefficients s₁=0.001, s₂=0.01, h₁=h₂=0.5, map length R=10. Simulations were performed for α=0, 0.05, 0.1, 0.25, 0.5, 0.75, 0.9, 0.95, 0.98 and 1. Selection is soft.