Occurrences of diploid and polyploid spined loaches (Cobitis elongatoides – taenia – tanaitica) in the river systems of the Western and Central Ukraine

Habitat Preferences of Diploid and Polyploids Spined Loaches (Сobitis elongatoides – taenia – tanaitica) in the River Systems of Western and Central Ukraine. Mezhzherin, S. V., Tsyba, A. A., Rostovska, O. V. –The analyzes the structure of diploid and polyploid populations within the spined loach group (Сobitis elongatoides – taenia – tanaitica) in the water systems of Western and Central Ukraine (Danube, Dniester, Southern Bug, Vistula, Middle and Upper Dnipro river basins). It reveals a bipolarity in settlement structure, characterized by a sharp prevalence of either diploids or polyploids, with no geographical trends in spatial distribution. Clonal hybrid polyploids, constituting 70% of the studied region's individuals, predominate in settlements along the main river channels, as well as in the middle and lower reaches of first and second-order tributaries. Populations where individuals of the parent species dominate are situated on the periphery: 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 of parent species by clonal hybrid polyploids is described as a universal phenomenon, linked to the advantages of parthenogenetic reproduction and higher survival rates of polyploids in modern ecological conditions.