Cortinarius section Bicolores and section Saturnini (Basidiomycota, Agaricales), a morphogenetic overview of European and North American species

Cortinarius is the largest genus of ectomycorrhizal fungi worldwide. Recent molecular studies have shown high levels of morphological homoplasy within the genus. Importantly, DNA phylogenies can reveal characteristics that have been either over- or underemphasized in taxonomic studies. Here we sequenced and phylogenetically analysed a large set of pan-European and North American collections taxonomically studied and placed in Cortinarius sect. Bicolores and sect. Saturnini, according to traditional morpho-anatomical criteria. Our goal was to circumscribe the evolutionary boundaries of the two sections, to stabilize both the limits and nomenclature of relevant species, and to identify described taxa which, according to our current understanding, belong to other lineages. Our analysis resolves two clades: /Bicolores, including 12 species, one of which is new to science, and /Saturnini, including 6 species. Fifteen binomials, traditionally treated in these two sections based on morphology, do not belong to the above two phylogenetic clades. Instead, six of these latter are clearly placed in other clades that represent sect. Bovini, sect. Sciophylli, sect. Duracini and sect. Brunneotincti. The presence or absence of blue pigments and the detection of specific odours emerge as clearly misleading taxonomic features, but more surprisingly, spore size and ecology can be misleading as well. A total of 63 type specimens were sequenced, 4 neotypes and 2 epitypes are proposed here, and 1 new combination is made.