Figure 6.

Left: effective population size $N_{\mathrm{e}}$ as a function of the standard deviation σ of $\ln s$ across loci, assuming a log-normal distribution of s and setting the average of $\ln s$ so that $\overline{s}=0.05$ for all values of σ. Solid curve shows prediction obtained by integrating Equation 34 over the distribution of s and over the genetic map; solid circles show simulation results. Parameter values: $N=20,000,$ $\alpha =0.9,$ $U=0.1,$ $R=10.$ In the simulations the heterozygous fitness effect $hs$ is the same for all mutations and adjusted so that $\overline{h}=0.25$ for all values of σ. Right: the distribution of s for $\sigma =0.1$ (solid curve), 0.5 (dashed curve), and 1 (dotted curve).