Dynamics of the variance components. The data correspond to the average variances computed over 10 simulations of the same high-line selection experiment (initial frequencies of H alleles: 3/7): Var(A), additive variance; Var(D), dominance variance; Var(I), interaction variance, including any kind of second- or higher-order epistasis, where Additive × Additive epistasis is the major component (not shown). The initial population, with intermediate frequencies, is close to the F2 population, with a low additive variance and a high epistatic variance. With the changes in allelic frequencies owing to the selection response, the epistatic variance component slowly decreases while the additive variance (and heritability) increases up to a maximum (between generations 10 and 15 under these conditions), which also corresponds to the maximum speed of the selection response (see Figure 3). The dominance component remains very low during the entire process, having a negligible impact on the overall dynamics.