Cryptic species diversity in polypores: the Skeletocutis nivea species complex

We propose a taxonomic revision of the two closely related white-rot polypore species, Skeletocutis nivea (Jungh.) Jean Keller and S. ochroalba Niemelä (Incrustoporiaceae, Basidiomycota), based on phylogenetic analyses of nuclear ribosomal internal transcribed spacer (ITS) and translation elongation factor EF-1α sequences. We show that prevailing morphological species concepts of S. nivea and S. ochroalba are non-monophyletic and we delineate new species boundaries based on phylogenetic inference. We recognise eleven species within the prevailing species concept of S. nivea (S. calidasp. nov., S. coprosmae comb. nov., S. futilissp. nov., S. imperviasp. nov., S. ipuletiisp. nov., S. lepidasp. nov., S. nemoralissp. nov., S. nivea sensu typi, S. semipileata comb. nov., S. unguinasp. nov. and S. yuchengiisp. nov.) and assign new sequenced epitypes for S. nivea and S. semipileata. The traditional concept of S. ochroalba comprises two independent lineages embedded within the S. nivea species complex. The Eurasian conifer-dwelling species S. cummatasp. nov. is recognised as separate from the North American S. ochroalba sensu stricto. Despite comprehensive microscopic examination, the majority of the recognised species are left without stable diagnostic character combinations that would enable species identification based solely on morphology and ecology.