Freshwater Mollusca of the circumpolar arctic: a review on their taxonomy, diversity and biogeography.
Since the end of the 19th century, the circumpolar fauna of freshwater Mollusca has not been reviewed despite the substantial increase of knowledge on this subject. A review of the freshwater mollusks of the Arctic based on an analysis of published data, own results and examination of museum collections is presented. 104 species of Mollusca have been registered, which constitutes less than 2% of the global diversity. The actual diversity of the Circumpolar freshwater molluscs may lie between 100 and 120 species. No endemic taxa are found in the Arctic. The most species-rich Arctic subregion is Siberia, whereas the North America maintains the poorest fauna. The aquatic malacofauna of Beringia is similar to that of North America, and Beringia as a biogeographic region constitutes a part of the Nearctic. The ways of formation of the Circumpolar malacofauna are discussed, with evaluation of dispersal, adaptation, and environmental filtering as the faunogenesis factors. The number of non-alien species in the Circumpolar freshwater malacofauna remains very low, and only one reliable occurrence of an alien species is known. Among the Arctic molluscs only three have a conservation status other than 'least concern' or 'data deficient', whereas most resident species are widespread and abundant.