About the Genetic Divergence of Populations Coupled by Migrations: Modern Modeling Based on Experimental Results of Yu.P. Altukhov and Coauthors

The existence possibility of stable differences in a selection-homogeneous range looks somewhat paradoxical from the population genetics point of view, but it is disruptive selection that can give such a divergence. Examples of population systems with stable divergence of the genetic structures of subpopulations living in a homogeneous area occur in nature and experimental systems. Comparison of these observations and modeling results allow us to explain the persistence of the stability of natural genetic divergence by the mechanism of interaction between disruptive selection (in the form of reduced fitness of hybrid forms) and a weak migration process. The results of experiments performed by Yu.P. Altukhov et al. with box populations of Drosophila melanogaster, in which the primary divergence of the genetic structures of the subpopulation at the α-GDH locus appeared, are in good agreement with this statement. One can assume the disruptive selection, in this case, the reduced fitness of heterozygotes in α-HDG, played the significant role in maintaining this divergence. An alternative hypothesis is genetic drift that fixed the differences. To identify and substantiate the possibility of the presence of this factor in a given system, and to assess the significant role that disruptive selection plays in maintaining the stability of primary genetic divergence, we analyzed mathematical models of the allele frequencies’ dynamics in a large panmictic population and in a system of 30 local migration coupled populations. Comparison of the simulation results with those of the experiment allows us to conclude with a high probability, in the considered experimental population system, there was a disruptive selection at the α‑GDH locus that facilitated the primary genetic divergence.