The genusCortinariusshould not (yet) be split

Abstract

AbstractThe genusCortinarius(Pers.) Gray (Agaricales, Basidiomycota) is one of the most species-rich fungal genera with thousands of species reported.Cortinariusspecies are important ectomycorrhizal fungi and form associations with many vascular plants globally. Until recentlyCortinariuswas the single genus of theCortinariaceaefamily, despite several attempts to provide a workable, lower-rank hierarchical structure based on subgenera and sections. The first phylogenomic study for this group elevated the old genusCortinariusto family level and the family was split into ten genera, of which seven were described as new. Here, by careful re-examination of the recently published phylogenomic dataset, we detected extensive gene-tree/species-tree conflicts using both concatenation and multispecies coalescent (MSC) approaches. Our analyses demonstrate that theCortinariusphylogeny remains unresolved and the resulting phylogenomic hypotheses suffer from very short and unsupported branches in the backbone. We can confirm monophyly of only four out of ten suggested new genera, leaving uncertain the relationships between each other and the general branching order. Thorough exploration of the tree space demonstrated that the topology on whichCortinariusrevised classification relies on does not represent the best phylogenetic hypothesis and should not be used as constrained topology to include additional species.For this reason, we argue that based on available evidence the genusCortinariusshould not (yet) be split.Moreover, considering that phylogenetic uncertainty translates to taxonomic uncertainty, we advise for careful evaluation of phylogenomic datasets before proposing radical taxonomic and nomenclatural changes.