Genetic Polymorphism and Differentiation of Populations of Sterlet Acipenser ruthenus (Acipenseridae) in the Lower Irtysh and Middle Ob Basins

The article presents data on polymorphism of intermicrosatellite sequences in the sterlet Acipenser ruthenus of the lower reaches of the Irtysh River and the middle reaches of the Ob River. We assessed intra- and interpopulation variability and genetic differentiation of A. ruthenus and revealed a high ISSR polymorphism in the species from the central part of the Ob-Irtysh basin. The proportion of polymorphic amplicons was 0.966, genetic diversity was 0.355, and the average number of alleles per locus was 1.97. The highest polymorphism was typical for the sterlet from the Tobol River at the confluence with the Irtysh River. Genetic differentiation between the sterlet groups of the Irtysh and Ob rivers is well pronounced, the interpopulation component accounts for 42% of variability (Gst = 0.42), gene flow is limited (Nm = 0.67). The sterlet groups inhabiting the Lower Irtysh from the mouth of the Tobol River to the mouth of the Konda River do not differ genetically and form one population (Gst = 0.08–0.12, Nm = 3.76–5.55). The sterlet from the Irtysh River within the Vagay region is genetically different from the other Irtysh samples (Gst = 0.22, Nm = 1.68) and belongs to a different population group. The differentiation between samples of sterlet from the Ob basin is higher than between samples from the Irtysh basin. Groups of sterlet from the Ob River and the Yuganskaya Ob canal are genetically different (Gst = 0.30, Nm = 1.19) and form various subpopulations. Spawning migrations, as well as confinement to wintering pits, play a decisive role in the formation of the sterlet population structure in the studied part of the distribution area. The identified sterlet population groups should be considered as separate units of environmental and economic management.