Fig. 4.

(Left) Response of the mean genotypic value to change in the effective population size, for the case in which the fitness function has width $\omega =\mathrm{5,000}$, and the ratio of mutation rates is $u_{01}/u_{10}=0.1$. (Upper Left) The effects of increasing the optimum phenotype ($\theta$), for the case in which there are $L=5$ sites. (Lower Left) The effects of increasing the number of sites from $L=2$ to 50, for the case in which the optimum phenotype is $\theta =2$. In both panels, the color-coded plotted points were obtained by computer simulations of a Wright–Fisher model, showing the near perfect agreement with the sequential-model approximation. (Right) Equilibrium genotype distributions (number of $+$ alleles) for situations in which $L=10$ (Top), 20 (Middle), and 50 (Bottom), with optimum genotypic value $\theta =7.0$ and width of the fitness function $\omega =\mathrm{5,000}$. Results from Eq. 6 are given for four effective population sizes.