Only 16 biotypes from 28 possible ones, which could be generated during hybridization of C. elongatoides, on the one hand, and representatives of superspecies C. taenia s. lato (С. taenia, C. tanaitica, C. species-1), on the other hand, were discovered in water areas of Ukraine. Furthermore, two biotypes, presumably C. aff. melanoleuca – tanaitica, were discovered in the north-western regions. Polyploids have compounded 65 % of investigated individuals of Сobitis genus, the average quantity of males has compounded less than 1 % and it was equal among triploids and tetraploids. Absence of amphidiploids and also lack of sufficiently large number of individuals with recombined genotype and abnormal electrophoretic spectra should be stressed. Two loci of polyploid biotypes formation are marked out: southern (the Lower Danube) and northern (the Upper Danube, Оder and Rhine). С. taenia and non-specified С. species, typical of the north-western basins of Ukraine, participate in formation of polyploids in the last mentioned river alongside with C. elongatoides and C. tanaitica. It is established that in spite of clearly evident expansion capacity, so-called southern biotypes (C. 2 (3) elongatoides – tanaitica, C. elongatoides – 2 (3) tanaitica) in comparison with the northern ones, which genome includes chromosomal complement С. taenia or С. species-1, are sharply limited in their spread to the East. The reason of such a situation is unbalanced gynogenetic crossing between females of the southern biotypes and С. taenia males, accompanied by introgressions, genetic instability and reduced posterity viability.