Phylogenetic relationships of russuloid basidiomycetes with emphasis on aphyllophoralean taxa

Abstract

Many homobasidiomycetes are characterized by a combination of gloeocystidia and amyloid basidiospores. They display a great variation in basidioma morphology, including erect and effused forms and gilled and nongilled forms. Earlier studies have shown these taxa to be related, and the group has been named the russuloid clade. Phylogenetic relationships among russuloid basidiomycetes were investigated using sequence data from the nuclear 5.8S, ITS2 and large-subunit rDNA genes. A dataset including 127 ingroup sequences representing 43 genera and ca 120 species were analyzed by maximum-parsimony and neighbor-joining methods. The sampling of taxa had an emphasis on nongilled taxa and two-thirds of the species possessed corticioid basidiomata. Thirteen major well-supported clades were identified within the russuloid clade. All clades except one include corticioid species. Ten characters from basidioma morphology and cultured mycelium were observed and evaluated. Results suggest that gloeocystidia are a synapomorphy for taxa within the russuloid clade while the amyloidity of spores is inconsistent. The ornamentation of spores and type of nuclear behavior seems to be informative characters at genus level. The agaricoid genera Lactarius and Russula are nested in a clade with corticioid species at the basal position. The new combinations Boidinia aculeata, Gloeodontia subasperispora, Gloeocystidiopsis cryptacantha and Megalocystidium wakullum are proposed.

• amyloid spores
• corticioid basidiomata
• gloeocystidia
• Homobasidiomycetes
• nuclear rDNA
• phylogeny
• russuloid clade
• sulfobenzaldehyde reaction

We are grateful to Drs Jacques Boidin, Sheng-Hua Wu, Leif Ryvarden and Jogeir Stokland for loan of collections; to Erast Parmasto, Ronald H. Petersen, Lennart Andersson, Nils Hallenberg and Roger Eriksson for valuable comments on earlier versions of the manuscript; to Andy Taylor for linguistic improvements and to David Hibbett and one anonymous reviewer for constructive comments. Financial support for this study was received from the Royal Swedish Academy of Sciences, Stiftelsen Anna-Greta och Holger Crafoords fond, Kapten Carl Stenholms donationsfond, Anna och Gunnar Vidfelts fond för biologisk forskning and Kungl. Vetenskaps- och Vitterhets-Samhället i Göteborg.