Stop black and white thinking: Russula subgenus Compactae (Russulaceae, Russulales) in Europe revised

Abstract

Russula subgenus Compactae is a group of ectomycorrhizal basidiomycetes, usually with large pileate fruitbodies. European members of the group are characterised by the absence of bright colours on the surfaces of their pilei, the context turning grey to black after cutting, the abundance of short lamellulae in the hymenophore, and spores with aninamyloid suprahilarspot and with low reticulate ornamentation. Ourmulti-locus phylogenetic study confirmed that this morphological delimitation corresponds to a well-supported clade. Within this clade,16 species are recognised in Europe, of which five belong to the R. albonigra lineage and were described in a previous study, while eleven are fully described in this study. The application of the names R. acrifolia, R. adusta, R. anthracina, R. atramentosa, R. densissima, R. nigricans and R. roseonigra is based on the position of sequences retrieved from types or authentic material. Based on type sequences, R. fuliginosa is synonymised with R. anthracina and two varieties of R. anthracina are considered synonyms of R. atramentosa. Theapplicationofthename R. densifolia is based on amorphological match with the traditional species interpretation and the neotypespecimen. Three species are described as new, R. marxmuelleriana sp. nov., R. picrophylla sp. nov. and R. thuringiaca sp. nov. This study recognises three major lineages and two species with isolated positions within the European Compactae and a orphological barcode was assigned to the species using an analysis of 23 selected characters. A search of publicly available sequences from the UNITE database revealed that the majority of species are host tree generalists and widely distributed intemperate and Mediterranean areas of Europe. Russula adusta is the only species so far proven to for mectomycorrhiza exclusively with conifers.