Heterocope borealis in Norway - A copepod on the move, or on the edge of its natural distribution?

Abstract

The calanoid copepod Heterocope borealis has been assumed to have an extremely northern distribution in Norway, limited to the north-eastern parts of Finnmark county. The recent records of the species in Lake Fustvatn and Lake Røssvatn in Nordland county was therefore quite unexpected. These lakes are located roughly 700 km south-west of the known distribution area in Norway. There is data on planktonic and/or littoral microcrustaceans from several hundred lakes between the known localities in Finnmark and the two new records in Nordland. The distribution of H. borealis in Finland and Sweden shows a scattered occurrence both in the northern and southern parts of the countries. Possible explanations for the occurrence of the species in the two lakes in Nordland are discussed.