Toward a better understanding of the infrageneric relationships in Cortinarius (Agaricales, Basidiomycota)

Abstract

Research on the molecular systematics of Cortinarius, a species-rich mushroom genus with nearly global distribution, is just beginning. The present study explores infrageneric relationships using rDNA ITS and LSU sequence data. One large dataset of 132 rDNA ITS sequences and one combined da-taset with 54 rDNA ITS and LSU sequences were generated. Hebeloma was used as outgroup. Bayesian analyses and maximum-likelihood (ML) analyses were carried out. Bayesian phylogenetic inference performed equally well or better than ML, especially in large datasets. The phylogenetic analysis of the combined dataset with species representing all currently recognized subgenera recovered seven well-supported clades (Bayesian posterior probabilities BPP > 90%). These major clades are: /Myxacium s.l., /subg. Cortinarius, the /phlegmacioid clade (including the subclades /Phlegmacium and /Delibuti), the /calochroid clade (/Calochroi, /Ochroleuci and /Allutus), the /telamonioid clade (/Telamonia, /Orellani, /Anomali), /Dermocybe s.l. and /Myxotelamonia. Our results show that Cortinarius consists of many lineages, but the relationships among these clades could not be elucidated. On one hand, the low divergence in rDNA sequences can be held responsible for this; on the other hand, taxon sampling is problematic in Cortinarius phylogeny. Because of the incredibly high diversity (~2000 Cortinarius species), our sampling included <5% of the known species. By choosing type species of subgenera and sections, our sampling is strongly biased toward Northern Hemisphere taxa. More extensive taxon sampling, especially of species from the Southern Hemisphere, is essential to resolve the phylogeny of this important genus of ectomycorrhizal fungi.

• Bayesian analysis
• ITS phylogeny
• maximum-likelihood analysis
• taxon sampling

This paper is based on ideas and suggestions of Meinhard Moser. Unable to thank him personally, we acknowledge his help by trying to continue Cortinarius research in his spirit. We thank Lorelei Norvell, Michelle Seidl and an unknown reviewer for their helpful suggestions, which certainly served to improve this paper. This work was financed by the NSF grants DEB-9708035 and DEB-0076023 to Jean-Marc Moncalvo and RV and by an Erwin Schrödinger Auslandsstipendium (J1821-BIO) grant from the Austrian Science Foundation (FWF) to UP.