Forgotten for two centuries: redescription of Phoxinus isetensis (Georgi, 1775) (Cypriniformes, Leuciscidae) – the most widespread minnow in Europe

Abstract

The morphology, phylogenetic position, and distribution of a recently revalidated species of leuciscid minnow, Phoxinus isetensis, were substantially clarified. The species was described in the late 18th century from the Middle Urals but later synonymized with Phoxinus phoxinus. As believed, P. isetensis is distributed in the Arctic Ocean catchment from the Murman coast via West and East Siberia until the Pacific Ocean catchment in Far East and Northeastern Asia. Our study, with the use of mtDNA markers coupled with extensive morphological data, showed that the distribution of P. isetensis is greatly different. Currently, this is the most widespread Phoxinus species in Europe, distributed in Northern and Western Europe and on the eastern edge of Siberia (Iset and Ural basins). In particular, P. isetensis inhabits the basins of the Caspian, Baltic, White, Barents, and Kara seas, possibly occurring in the North Sea basin. The species was redescribed, and the type locality and neotype were designated. The main morphological difference from other Phoxinus spp. is the large total number of vertebrae (39–43, mode 41) due to an increase in the number of caudal vertebrae (16–21, mode 19). Phylogenetically, P. isetensis is a sister to the Caucasian species P. colchicus (p-distance = 5%). The wide distribution of P. isetensis within the area of the Last Glacial Maximum suggests rapid colonization of deglaciated regions, probably due to its adaptation to a cold climate.