Morphological variation and taxonomic status of Altai osmans, Oreoleuciscus, from the upper reaches of the Ob River system

The morphology of the endemic Altai osmans Oreoleuciscus spp. (Cyprinidae), from headwaters of the Ob tributaries in the Altai Republic (Russia), Terekhol Lake in the Tuva Republic (Russia), and the Chovd Gol River drainage and related bodies of water (Mongolia), where they are one of only four fish species occurring in most bodies of water were examined. Their high degree of morphological variation makes species determination problematical. Analysis of six meristic counts and principal component analysis (PCA) of 21 morphological measurements discriminated two species, Oreoleuciscus potanini and O. humilis . The results suggest that only O. potanini occurs in the upper reaches of the Ob system. The systematics and biogeography of Oreoleuciscus are discussed.