SPATIAL SEGREGATIN OF DIPLOID AND POLYPLOID SPINED LOACHES, COBITIS ELONGATOIDES-TAENIA-TANAITICA (CYPRINIFORMES, COBITIDAE), IN RIVER SYSTEMS OF WESTERN AND CENTRAL UKRAINE.

The investigation examines the structure of diploid and polyploid populations within the spined loach group (Cobitis elongatoides-taenia-tanaitica) in the water systems of Western and Central Ukraine, including the Danube River, Dniester River, Southern Bug River, Vistula River, Middle and Upper Dnipro River basins. The study reveals a bipolarity in settlement structure, with a sharp prevalence of either diploids or polyploids, and no discernible geographical trends in spatial distribution. Clonal hybrid polyploids, which make up 70 % of the individuals studied in the region, are most common in settlements along the main river channels, as well as in the middle and lower reaches of first and second-order tributaries. Populations where diploid specimens of the parent species are predominant are located in accessory systems, tributaries of the third and higher orders, upper reaches of first and second-order tributaries, and lakes. This spatial segregation arises from historical circumstances rather than ecological preferences, primarily due to the distance from water corridors through which polyploids invaded in the 1960s-1970s. The displacement of diploid individuals by clonal hybrid polyploids is a universal phenomenon. This is due to the advantages of parthenogenetic reproduction and higher survival rates of polyploids in modern environmental situations. [ABSTRACT FROM AUTHOR]