Effect of selection strength and SGV on the frequency ratio E[<i>x</i>].

We contrast the expected allele frequency ratios of the first minor locus (with the second highest frequency) over the major locus (with the highest frequency) for 2 loci (blue dots) and for 10 loci (orange dots) with analytical predictions (Appendix, Eq M.16, black curve). E[x] is shown as a function of Θbg (= Θl for the 2-locus case). Panels correspond to different strengths of positive selection (sb, rows) and levels of SGV (no SGV, strongly deleterious sd = −0.1, weakly deleterious sd = −0.001, columns). We find that neither factor alters the expected ratio. We do not obtain results for Θbg ≥ 10 and sd = −0.001, where strong recurrent mutation overwhelmes weak selection, such that mutant alleles fix even before the environmental change. Results for 10 000 replicates, standard errors < 0.005 (smaller than symbols).