Studies of New Zealand Cortinarius: resolution of taxonomic conflicts in section Subcastanelli (Agaricales), new species and key to rozitoid species

Cortinarius is a speciose genus of mycorrhizal fungi that contains many cryptic and difficult to delineate taxa. Correct identification can be confounded for species where no genetic information is available from their respective type specimens. Cortinarius section Subcastanelli is known to contain several species for which there is ambiguity around their true identity, i.e. C. epiphaeus, C. subcastanellus and C. taylorianus. For example, it has been long hypothesised that C. napivelatus is conspecific with C. epiphaeus. In this study, the nuclear ribosomal internal transcribed spacer (ITS) region was sequenced from the holotypes of the afore mentioned species. The ITS sequences and morphological characteristics indicated that C. epiphaeus and C. napivelatus were conspecific. Consequently, C. napivelatus was synonymised with C. epiphaeus. Based on morphological and molecular evidence it is shown that the protologue of C. subcastanellus is a mixture of two species. Consequently, the morphologically similar C. wallacei is synonymised with C. subcastanellus, the protologue of C. subcastanellus is emended and the new species C. cesarioanus is erected. Similarly, C. taylorianus was found to be polyphyletic. The holotype of C. taylorianus was nested in section Archeriani while a paratype fell in section Subcastanelli. As the protologue is consistent with the clade containing the type, no emendations are required. In addition to the species in Subcastanelli, a new species in Delibuti is described: C. viridipileatus. This species is distinctive in section Delibuti in having a green pileus with mauve lamellae. Finally, a key to New Zealand rozitoid species is presented.

Automated summary

Cortinarius is a diverse genus of mycorrhizal fungi, with some species like C. epiphaeus and C. taylorianus proving difficult to identify. In species where genetic information is lacking from type specimens, accurate identification may be challenging.