Figure 1
F ST (Fixation index) and allele frequency analysis. (A) HGDP-CEPH populations are shown on a world map and color coded according to their Δphotoperiod (in topological color scale, minimum = orange, maximum = dark blue). Arrows denote populations included in FST pairwise comparisons, with red and green indicating a significant excess of variants with an FST rank >0.95 or <0.05, respectively (among the 84 SNPs in circadian rhythm genes, see text). Gray arrows denote pairwise comparisons that showed non-significant excess of high FST variants. Fisher's exact test P values (see text) for FST comparisons are as follows: Orcadian-Biaka Pygmy, 0.02; Orcadian-Mbuti Pygmy, 0.05; Orcadian-Yoruba, 0.05; Russian-Biaka Pygmy, 0.03; Russian-Mbuti Pygmy, 0.03; Russian-Yoruba, 0.08; Papuan-Biaka Pygmy, <0.01; Papuan-Mbuti Pygmy, <0.01; Papuan-Yoruba, <0.01; Papuan-Yakut, 0.12; Yakut-Maya, 0.03; Yakut-Karitiana, 0.02; Maya-Biaka Pygmy, <0.01; Maya-Mbuti Pygmy, <0.01; Maya-Yoruba, <0.01; Karitiana-Biaka Pygmy, <0.01; Karitiana-Mbuti Pygmy, <0.01; Karitiana-Yoruba, <0.01. (B) Box-plot of normalized derived allele frequencies for the 84 SNPs significantly correlated with Δphotoperiod (left) and for 840 minor allele frequency (MAF)-matched control variants (right). Populations are color coded as in panel (A) and are grouped in six broad geographic areas; within these areas populations are ordered according to increasing Δphotoperiod. (C) Pairwise FST for all HGPD-CEPH populations calculated for the 84 Δphotoperiod-selected variants (left) and for 840 MAF-matched control SNPs (right). Pairwise FST percentile ranks are reported in gray scale (FST rank increasing with gray shading). Populations are ordered as in (A).