‘Cort short on a mountaintop’ – Eight new species of sequestrate Cortinarius from sub-alpine Australia and affinities to sections within the genus

Abstract

During the course of research on mammal mycophagy and movement in the Northern Tablelands of New South Wales, Australia, extensive collections of sequestrate fungi were made, including numerous cortinarioid taxa. Historically any novel taxa would have been described in the cortinarioid sequestrate genera Descomyces, Hymenogaster, Protoglossum, Quadrispora, Thaxterogaster or Timgrovea based on broad morphological similarities of the sporocarps and spore ornamentation. However, consistent with other recent analyses of nuclear DNA regions, taxa from sequestrate genera were found to have affinities with Cortinarius and Descolea or Hebeloma, and to be scattered across many sections within Cortinarius. None of the historical sequestrate cortinarioid genera are monophyletic in our analyses. In particular, the gastroid genus Hymenogaster is paraphyletic, with one clade including two species of Protoglossum in Cortinarius, and a second clade sister to Hebeloma. Eight new species of sequestrate Cortinarius are described and illustrated, and discussion of their affinities with various sections provided: C. argyronius, C. caesibulga and C. cinereoroseolus in section Purpurascentes, C. maculobulga in section Rozites, C. sinapivelus in section Splendidi, C. kaputarensis in a mixed section Phlegmacium/Myxacium within a broader section Dermocybe, C. basorapulus in section Percomes and C. nebulobrunneus in section Pseudotriumphantes. Keys to genera of the Bolbitiaceae and Cortinariaceae containing sequestrate taxa and to currently known Australian species of sequestrate Cortinarius and Protoglossum are provided. As with the related agaricoid taxa, macroscopic characters such as colour and texture of basidioma, degree of loculisation of the hymenophore, and stipe-columella development and form remain useful for distinguishing species, but are generally not so useful at the sectional level within Cortinarius. Microscopic characters such as spore shape, size, and ornamentation, and pileipellis structure (simplex vs duplex and size of hyphal elements) are essential for determining species, and also appear to follow sectional boundaries.