Figure 5.—

Mutation-rate equilibria. Results for N = 500, t_mut = 0.01, = 0.1, and U₀ = 0.025 are shown. (A) f = 1.1, t_let = 0, Q = 0.5; (B) f = 1.3, t_let = 0, Q = 0.2; (C) f = 1.5, t_let = 0.1, Q = 0.05. The solid black curve and left y-scale show the fitness. The red curves show the fluctuations in fitness-loss rate around their median value indicated by the dotted line. The blue curves show the fluctuations in mutation rate around their median value, also on the dotted line. The scale for the relative rate fluctuations on the right y-axis shows the instantaneous value divided by the median; see Table 2 for numerical values. The instantaneous fitness-loss rate was calculated as a running average over 2 × 10⁴ generations from the slope of the logarithm of fitness vs. time.