PS bias was estimated as mean PS minus mean trait measure, after standardizing both quantities against the reference population. FST with PS reference populations was estimated using vcftools 0.1.1637 and the option -weir-fst-pop <P1> -weir-fst-pop <p2>, where p1 and p2 are all the analyzed groups. In all analyses described in this section and in the boxplots in Figs. 2, 4 and Supplementary Fig. 5, we removed aspPS obtained from less than 10% of the genome.
