Figure 3.—

Fixation time for a single-step increase in mutation rate. Results for N = 500, = 0.1, t_mut = 0.01, and t_let = 0 (squares and solid lines) or t_let = 0.1 (crosses and dashed-dotted lines) are shown. The mean fixation times from 30 replicate simulations are shown. Red symbols and upper x-scale: starting from U₀ = 0.0025 (N_eb = 476 from Equation 1), mutators with a given increment f are introduced. Blue symbols and lower x-scale: starting from a 10 times higher U₀ = 0.025 (N_eb = 330 from Equation 1). The curves are the theoretical expression in the text; assuming that s_m is proportional to f − 1, the best-fit parameters are = 4.1 × 10⁴ and s_mN_eb = 1.06 × (f − 1) (solid red line), = 4.2 × 10⁴ and s_mN_eb = 1.15 × (f − 1) (dashed-dotted red line), = 4.7 × 10³ and s_mN_eb = 5.2 × (f − 1) (solid blue line), and = 4.6 × 10³ and s_mN_eb = 6.1 × (f − 1) (dashed-dotted blue line).