A molecular phylogeny of the Russulales including agaricoid, gasteroid and pleurotoid taxa

The Russulales consists of agaricoid, gasteroid and hypogeous gasteroid taxa of basidiomycetes closely related to Russula and Lactarius. Because there have been no molecular phylogenetic studies of the Russulales, attempts at formulating a natural classification for these taxa have met with difficulty. In this study, nuclear large subunit rDNA (n-LSU) was used to infer phylogenetic relationships among members of the Russulales including agaricoid, tropical pleurotoid and annulate taxa, and gasteroid and hypogeous gasteroid genera. Analysis of the n-LSU region indicated that Russula sensu strictu (excluding gasteroid and hypogeous gasteroid taxa) can be considered polyphyletic with two well supported groups, one group arising separately from the main body of the tree and one group basal to Lactarius. Russula sensu late can be considered paraphyletic with gasteroid and hypogeous gasteroid forms nested in the same clades alongside agaricoid taxa. Lactarius sensu late was found to be a monophyletic group that includes agaricoid, gasteroid and hypogeous gasteroid taxa. Gasteroid and hypogeous gasteroid genera were scattered throughout the order, with Macowanites, Gymnomyces, Cystangium and Martellia nested within Russula, while Zelleromyces and Arcangeliella grouped within Lactarius. Most of the gasteroid and hypogeous gasteroid genera appear to be polyphyletic and their position was supported within established infrageneric taxa of Russula and Lactarius. These results suggested that synonomy of gasteroid genera into Russula and Lactarius is justifiable.