Phylogenetic conundrum of the mushroom-forming fungi (agaricomycetes)

The problem of the origin and phylogeny of Agaricomycetes remains controversial. However, various data accumulated in recent decades provide an opportunity to reach some definite conclusions. The conclusions are: 1) Final establishment of the circumscription of the class Agaricomycetes (Basidiomycetes with dolipore septa without nanopores, with perforated, or rarely unperforated, parenthosomata), and the proof of their evolutionary advancement compared with Tremellomycetes; 2) The loss of taxonomic status of such groups as Hymenomycetes/Gasteromycetes and Aphyllophorales; 3) The appearance, in the course of studies of rDNA, of some “molecular concepts”, the most important of which are the rooting of Agaricomycetes within the Dacrymycetales/Auriculariales and the basal position of taxa with unperforated parentosomes; 4) Proof of evolutionary advancement of brown-rot fungi with considerable devaluation of the type of rot as a character in taxonomy of Basidiomycetes; 5) Proof of secondary origins of corticioid and gasteroid forms. Any phylogenetic reconstruction of Agaricomycetes should be based on the aforesaid concepts. However, some of the remaining difficulties and contradictions in the field of systematics are analyzed in the present chapter.