Figure 1

(a)-(c): P -values of Wilcoxon tests plotted against the female fraction of effective population size, r = Nf /( Nf + Nm ), as r varies on the interval [0,1] for (a) the worldwide dataset treated as seven regions (World-7), (b) Eurasia treated as one region (Eurasia-1) and (c) Oceania. Each point represents the P-value of the Wilcoxon test between the X-chromosomal and autosomal within-population variance components, with autosomal values being transformed according to (7) for a particular value of r. (d)-(f): Boxplots of autosomal within-population variance components transformed using equation (7), and observed non-pseudoautosomal X-chromosomal within-population variance components for different values of r. r = 0.875 (z ≈ 0.143) corresponds to the untransformed autosomal values; r = 0.5 occurs when drift proceeds at the same rate in males and females; r = 0.12 provides the maximum P-value across values of r for the two-sided Wilcoxon test with the World-7 dataset. Note that, as r changes, the two plots across genetic systems coincide for the World-7 and Oceania datasets, but remain quite distinct for the Eurasia-1 dataset (as reflected by the P-values of the specific comparisons shown)