Abstract
Four new Hydnellum species are described. Hydnellum roseoviolaceum sp. nov. grows in dry pine heaths on acidic, sandy soil. It is close to H. fuligineoviolaceum, another pine-associated species, but differs by smaller spores, an initially rose-coloured instead of violet flesh in fresh basidiomata and a mild taste. Hydnellum scabrosellum sp. nov. grows in coniferous forests on calcareous soil. It shares a general morphology with H. scabrosum, which also is its closest relative. It differs by having smaller and slenderer basidiomata and by the yellowish ochraceous colour of flesh and spines in dried specimens compared to the whitish or reddish brown colour seen in H. scabrosum. Hydnellum fagiscabrosum sp. nov. is another species with morphological and phylogenetic affinities to H. scabrosum. However, it is associated with trees from Fagales whereas H. scabrosum is associated with Pinaceae. Hydnellum nemorosum sp. nov. is yet another species that associates with broadleaved trees. It seems to be a rare species, morphologically reminiscent of H. fuligineoviolaceum, H. ioeides and H. scabrosum, but it is phylogenetically close to H. fennicum. Sequences from the type specimens of H. glaucopus, H. lepidum, H. scabrosum, Sarcodon illudens and S. regalis are included in the analyses. Specimens given the provisional name "Sarcodon pseudoglaucopus" in Sweden are now shown to be referable to S. illudens. The analyses further showed that S. illudens is close to H. lepidum. The new combination Hydnellum illudens is proposed. Sarcodon regalis and H. lepidum are shown to be conspecific and, although their basionyms were simultaneously published, the name S. regalis was only validated in a later publication. Hydnellum lepidum therefore takes priority and S. regalis becomes a synonym. Citation: Nitare J, Ainsworth AM, Larsson E, Parfitt D, Suz LM, Svantesson S, Larsson K-H (2021). Four new species of Hydnellum (Thelephorales, Basidiomycota) with a note on Sarcodon illudens. Fungal Systematics and Evolution 7: 233-254. doi: 10.3114/fuse.2021.07.12.