Figure 9.

Fixation probability of the mutant type, A, as a function of (half) the width of the resident’s fitness distribution, Δ_b. The fitness values for the resident are either $\overline{b}-{\mathrm{\Delta }}_b$ or $\overline{b}+{\mathrm{\Delta }}_b$, where $\overline{b}=1$. Again, every location in environment 1 (resp. 2) is a neighbour to two individuals in environment 2 (resp. 1). The population size is N = 100, and $\overline{a}\in \{0.8,0.9,1.0,1.1\}$. The results are obtained from exact solutions of the Kolmogorov equation for fixation probability. As Δ_b grows, a near-neutral mutant’s fixation probability increases, consistent with amplification.