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The Coregonus lavaretus (Linnaeus, 1758) complex is a morphologically and genetically diverse group of whitefish. Its taxonomic structure has been controversial for almost a century. At least 25 forms of C. lavaretus have been described in Siberia, but there is still no consensus on their intraspecific structure and taxonomy. Coregonus lavaretus pidschian (Gmelin, 1789) was described as a subspecies of C. lavaretus. Recently, it was assumed that this subspecies is also a complex. The purpose of this study was to compare the distributions of pidschian-like whitefish haplotypes in two basins of large Siberian rivers, Yenisei and Lena, and to assess the gene flow between basins of these rivers, which were connected after the last glaciation. The sequence of the following mitochondrial DNA genes, 16S rRNA (partial), tRNA-Leu (full), NADH dehydrogenase subunit 1 (full), tRNA-Ile (full), and tRNA-Gln (partial), were used for the inference of intraspecific genetic structure of C. l. pidschian. Whitefish haplotypes were clustered into two groups according to their distribution between two large Siberian river basins; however, there were shared haplotypes indicating events of migration and hybridization, which could occur when Bolshoi Yenisei and Lena river systems were connected after the last glaciation (the Late Pleistocene). info:eu-repo/semantics/acceptedVersion

The sterlet (Acipenser ruthenus Linnaeus, 1758) is a relatively small sturgeon widely distributed in Eurasian rivers from the Danube to the Yenisei. During the twentieth century, all wild sterlet populations have declined due to anthropogenic factors including: overfishing, poaching, construction of dams, and pollution. Despite the necessity of characterization both wild and captive stocks, few studies of population genetics have been performed thus far. Here we studied the genetic diversity and geographic structure of sterlet populations across the eastern range – Ob-Irtysh and Yenisei basins – by sequencing a 628-bp fragment of mitochondrial DNA control region. We identified 98 new haplotypes, delineated 12 haplogroups and estimated the time of basal haplogroup divergence within the species as over 8 million years ago. Our data suggest that Ob-Irtysh and Yenisei populations are isolated from each other and much lower genetic diversity is present in the Yenisei population than in the Ob-Irtysh population. Our data imply that sterlet populations in Siberian rivers underwent bottleneck or fragmentation, followed by subsequent population expansion. The data obtained here are important for sterlet population monitoring and restocking management.

The article offers a general view of the graylings (Thymallidae) from the largest Siberian river basins, namely those of the Ob and Yenisei, including the Khantayskoye and Baikal Lakes. It provides data on some of the most important morphological features. It is shown that it is erroneous to consider the graylings only within the subspecies Thymallus arcticus arcticus. The reservoirs of the Altai-Sayan highlands, which drain to the north into the inland waters of Mongolia, should also be considered, as one of the two major centres of speciation and morphogenesis for graylings.