Causes of Morphological and Genetic Heterogeneity of White Fish <i>Coregonus lavaretus</i> sensu lato in the Arctic Part of the Lena River Basin

The results of the morphological and genetic analysis of populations/forms/species of tanned whitefish from the middle and lower reaches of the river are presented. Lena, and adjacent rivers. There are reasons to believe that, despite the significant heterogeneity of whitefish in Siberia, a small number of stable forms/species inhabit the water bodies of the Siberian Arctic. These are East Siberian (C. lavaretus pidschian n. brachymystax), glacial plain (C. lavaretus pidschian n. glacialis), and Yukagir whitefish (C. lavaretus pidschian n. jucagiricus), as well as their hybrid populations. The glacier-plain whitefish and its derivatives differ from the East Siberian whitefish in plastic features, but they are identical in meristic ones. Molecular genetic studies have shown that in most glacier-plain whitefish form extensive loosely connected networks of haplotypes, which corresponds to the long-term existence of populations in favorable conditions. The East Siberian whitefish haplotypes are closely related to the whitefish haplotypes from the water bodies of Southern Siberia and have a radial structure. Such a structure of median networks indicates a recent decline in the number of East Siberian whitefish followed by expansion, which is directly related to the events of the Quaternary glaciations.