Figure 2 .

Expected behavior when the effects of deleterious mutations are exponentially distributed with mean σ. (a) Steady-state fraction of mutators in the population, p_m, in units of $\text{σ}/\text{γ}$. The exact result, Equation 21, is shown in red. The approximations for weak and strong selection relative to mutation, M/σ ≪ 1 and M/σ ≫ 1 in Equation 22, are shown in blue and green, respectively. (b) Dynamics of p_m, from Equation 21, in units of $\text{σ}/\text{γ}$. In red, α = 0.2, and in blue α = 5. Note that δ_m increases linearly at rate γ for $t\ll 1/M$ (red line) or $t\ll 1/\sqrt{M\text{σ}}$ (blue line), before saturating at its steady-state value. (c) Average deleterious load δ_m of a mutator. The exact result, Equation 23, is shown in red. The approximations for M/σ ≪ 1 and M/σ ≫ 1 in Equation 24 are shown in blue and green, respectively. Note the results in b and c make use of the approximation λ ≫ 1.