Entoloma aurorae-borealis sp. nov. and three rare Entoloma species in the Sinuatum Glade (subg. Entoloma) from northern Europe

Entoloma aurorae-borealis is described as new to science and three rare or little known Entoloma species (E. borgenii, E. eminens, and E. serpens) from Norway are treated based on morphological and molecular evidences. In the ITS phylogeny presented here, all species belong to the Sinuatum Glade, one of five well-supported lineages of subgenus Entoloma (= Rhodopolia & Nolanidea). Entoloma aurorae-borealis is only known from northern Norway, whereas E. eminens and E. serpens, apart from the here reported new records in Norway are known only from a few localities in Finland, and E. serpens also in NW Russia. Entoloma borgenii is a wide-spread, though rarely recorded species from alpine sites in north Norway as well as the arctic (Greenland, Svalbard) and a few places in northern and eastern Finland. The two arctic-alpine species (E. aurorae-borealis and E. borgenii) are associated with Salix herbacea, E. serpens grows with Salix spp. and probably also with Betula and Populus in borealboreonemoral (-alpine) areas, and E. eminens in Norway is associated with Tilia and Corylus in a boreonemoral area. In Finland it is apparently associated with boreal deciduous trees. Full descriptions are given, as well as notes on the variability, ecology and geographic distribution of each species.