SUMMARY. The diploid-polyploid complex of European spined loaches of the genus Cobitis is a traditional model for studying genetic migrations. The river systems of Ukraine, where two genetically and geographically polar groups of populations are located, provide optimal conditions for comparing the peculiarities of genetic migrations in diploids and polyploids. The northwestern group is marked by the rare Ldh-Ba gene, which simultaneously in diploids and polyploids penetrates hundreds of kilometers into populations possessing the genus-typical Ldh-Ba gene. Comparison of gene flows shows: (i) the length of the gene flow from west to east in polyploids is twice as great as in diploids; (ii) the average frequency of carriers of the introgressed gene in the gene flow of polyploids is three times higher than in diploids; (iii) the gene flow in diploids manifests as a gradual change in carrier frequencies, whereas in polyploids it shows abrupt (stepwise) changes in frequencies; (iv) genetic migration in diploids is limited by a number of bioclimatic factors, while in polyploids it is practically independent of abiotic environmental factors. The reason for these differences is the greater tolerance of polyploids, characterized by low metabolic rates, to oxygen deficiency in water, as well as their ability to found populations at the level of single individuals. These two circumstances ensure extensive migrations in polyploids.
Keywords: genetic migrations, bioclimatic factors, diploid-polyploid complex, Cobitis, genogeography, Ldh-B, river systems of Ukraine
