Selective structure of the gene pool: IV. Estimation from selection intensity index R-s

A new approach for investigating the selective structure of the gene pool r eflecting the type and intensity of selection is proposed. Selection pressu re is estimated on the basis of interpopulation gene diversity with the use of the selection intensity index: R-S(i) = NeS(i) = 1/4(1/(FST(i)) - 1/F-e ). Distributions of R-S(i) in gene pools of indigenous populations from all continents and five subregions of the northeastern Eurasia were examined. It was shown that, of all theoretical distributions, only beta-distribution s provide a good approximation of R-S(i) estimates. Based on the confidence intervals of (R) over bar(S) obtained from beta-dis tributions, genes can be grouped into the three following classes according to their selective structure: LOWER DIFF, NEUTRAL, and SUPER DIFF. These c lasses, respectively, include genes subjected mainly to stabilizing selecti on (R-S(i) > 0; LOWER DIFF), genes subjected mainly to differentiating sele ction (R-S(i) < 0; SUPER DIFF), and arbitrarily selectively neutral genes ( R-S(i) approximate to 0; NEUTRAL). Simulation of gene pool sampling (10(6) samples from 50 markers for each gene pool) allowed us to characterize the selective structure by determining markers that fall into the same selectiv e class irrespective of the variant for the sampling process. The selective structure of gene pools from six continents (Europe, Asia, Africa, Austral ia, America, and southeastern Eurasia) and five subregions of northeastern Eurasia was characterized. It was shown that approximately one-third of gen es is subjected to selection irrespective of the hierarchical level of the region. In gene pools of Europe, northeastern Eurasia, and European and Ura l subregions, the proportion of genes under stabilizing selection was highe r; the proportion of selectively neutral genes, lower. Debatable issues of tests for selective neutrality based on heterogeneity of interpopulation ge ne diversity are considered. These issues include the;effect on:F-ST Of the hierarchical population structure,; sample size, number of subpopulations, and other factors that shift estimates of gene selective values.