On the Role of Natural Selection in Genetic Divergence of Migration-Coupled Populations. Frequency-Dependent Selection

This article proceeds with the study of the mechanisms of primary genetic divergence of migratory-coupled populations. The modeling is based on the experiment performed by Yu.P. Altukhov and co-authors with box populations of Drosophila melanogaster. This experiment demonstrated the primary divergence of the genetic structures of the subpopulation for two loci – markers of genetic diversity (α-GDH and esterase-6). Previously, we showed that disruptive selection acted with a high probability for the α-GDH locus in the experimental system, which ensured the maintenance of the observed primary genetic divergence. This work is devoted to identifying the mechanisms that contributed to the primary genetic divergence for the esterase-6 locus. We analyzed mathematical models with discreet time for the dynamics of allele frequencies in a large panmictic population and in a system of 30 local migratory-coupled populations. Comparison of the simulation modeling results with the experimental ones allows us to conclude that, with a high probability, in the experimental population system under consideration, frequency-dependent selection at the esterase-6 locus acted against the background of density-dependent selection. With uniform selection in subpopulations connected by small migrations, this type of selection is shown to promote divergence, and genetic divergences in neighboring populations are significantly more pronounced than they could be under conditions of genetic drift.