Corticioid fungi

The corticioid fungi are a group of fungi in the Basidiomycota typically having effused, smooth basidiocarps (fruit bodies) that are formed on the undersides of dead tree trunks or branches. They are sometimes colloquially called crust fungi or patch fungi. Originally such fungi were referred to the genus Corticium ("corticioid" means Corticium-like) and subsequently to the family Corticiaceae, but it is now known that corticioid species are not closely related. The fact that they look similar is an example of adaptive evolution. Since they are often studied as a group, it is convenient to retain the informal (non-taxonomic) name of "corticioid fungi" and this term is frequently used in research papers and other texts.

The genus Corticium was established by Persoon in 1794 for fungi having smooth, effused fruit bodies. Corticium roseum Pers. was later selected as the type species. Subsequent authors described over 1000 species in the genus which continued to be used in its wide sense up until the 1950s. Though a number of genera had been recognized as distinct from Corticium from the late nineteenth century onwards, it was not until Swedish mycologist Prof. John Eriksson reviewed the corticioid fungi in a series of publications starting in 1950 that modern concepts were formed. The eight-volume work that he initiated, Corticiaceae of North Europe (1973-1987), effectively established the current circumscription of the corticioid fungi.

Eriksson and his co-authors, however, still placed all or most of these fungi within the Corticiaceae, though stating that this was "not a natural taxon but an assemblage of species with similar habitat." It was not until the advent of DNA sequencing that the full diversity of these fungi was realized. The genus Corticium is still retained, but is now restricted to a few species closely related to the type. The Corticiaceae is now equally restricted to a few genera close to (and including) Corticium. Crust-like species are found in no less than 18 of the 24 currently recognized orders of higher basidiomycetes (Agaricomycotina).

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