Thaxterogaster revisited: A phylogenetic and taxonomic overview of sequestrate Cortinarius from Patagonia

Abstract

In the Patagonian region, Cortinarius is the most diverse and abundant genus of ectomycorrhizalfungi with at least 250 species. Sequestrate forms were until recently documented within the genusThaxterogaster, a genus now known to be polyphyletic, and many were consequently transferred toCortinarius. Original descriptions were mostly available in German and Spanish and interpretationsof morphological structures outdated. Despite recent advances in Cortinarius systematics, thecurrent classification, diversity, and ecology of sequestrate ?cortinarioid? fungi in Patagonia remainunclear. The objective of this study was to provide an update on sequestrate Cortinarius of southernSouth America. We documented each species with morphological descriptions, photographs,basidiospore scanning electron microscopy (SEM) images, and molecular characterization usingnuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS) and nuc 28S rDNA (28S) sequencedata. Original descriptions of taxa were also translated to English and revised based on freshcollections. We documented 24 species from Patagonia based on molecular data and conductedmorphological and phylogenetic analysis for 18 previously described species based on type andreference specimens. In addition, we formally described two new species. Four additional taxa wereprovisionally determined as new but require further study. New ITS sequence data were producedfrom eight type specimens. We also provide a new name, Cortinarius gloiodes, nom. nov., for thetaxon previously described as Thaxterogaster gliocyclus. In addition to the species treated in detail,we provided additional reference information and discussion on six described species thatremained incompletely known or for which no recent collections were found. Of the 24 taxadocumented from Patagonia, 15 species were assigned to 12 current sections in the genusCortinarius. Analysis of spore ultrastructure showed that sequestrate forms of PatagonianCortinarius lack a true perisporium.