The evolutionary origin of the universal distribution of mutation fitness effect
Fig 3
The frequency of deleterious alleles decays exponentially with their fitness effect, with the slope increasing in time.
(A) Analytic prediction for the frequency of deleterious alleles from Eq 5 agrees with Monte-Carlo simulation. X-axis: Mutation cost of deleterious allele at a genomic site, s. Y-axis: Frequency of deleterious alleles at such a site, f(s). The mutant frequency f is averaged over 20 random simulation runs, the straight lines are linear regression. Different colors show different times, symbols are simulation, and lines are analytic prediction (Eq 5). The numbers on the curves are the values of the slope. Parameters as in Fig 2. (B) The slope of the distribution of deleterious alleles β, analytic (blue lines) and simulation (purple lines), as a function of time, t. Parameters fin and sav, if different from those in Fig 2, are shown on the legend. The log-slope for the simulated curves of mutant frequency in (A) is obtained by an exponential fit. We observe that the deviation of the simulated slope from the analytic prediction Eq 5 at long times coincides with the establishment of the traveling regime, which occurs later for smaller sav (Fig 2F). At long times, the traveling wave prediction, Eq 8, applies (dashed blue lines). Grey diagonal shows β(t) = t. Parameters are as in the legend of Fig 2.