Figure 4

Principal components analysis performed on 1,000-marker subsets of simulated data under three simulated migration schemes and three simulated ascertainment-bias conditions, as compared to the empirical data. ( a ) No migration; ( b ) low taurine–indicine gene flow; and ( c ) low taurine–indicine gene flow, plus higher recent indicine to Africa gene flow. Ascertainment schemes: (I) SNPs were based on random samples of loci (no bias); (II) sampled loci were selected from those that were polymorphic within Europe; and (III) sampled loci were selected from loci that were polymorphic in two or more subpopulations. Proportions of variation accounted for by the first two PC axes are labeled on the figure.