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 all corticioid species are not necessarily closely related. The fact that they look similar is an example of convergent 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.
Description and Diversity:
Corticioid fungi are rather loosely defined, but most have effused fruit bodies, the spore bearing surface typically being smooth to granular or spiny. Some species (in the genera Stereum and Steccherinum, for example) may form fruit bodies that are partly bracket- or shelf-like with a smooth to spiny undersurface.
The corticioid fungi currently comprise around 1700 species worldwide, distributed amongst some 250 genera. They constitute around 13% of the homobasidiomycetes known to date.
Habitat and Distribution:
Most corticioid fungi are wood-rotting species and rely on wood degradation as their primary means of nutrition. Although the fruiting bodies are formed on the underside of dead branches or logs, the fungus resides within the wood. A number of species are litter-rotting and produce fruit bodies underneath fallen leaves and compacted litter as well as on fallen wood. Some of these species are known to be ectomycorrhizal (forming a beneficial association with the roots of living trees). A few specialist species grow on dead herbaceous stems and leaves or on dead grass, rush, and sedge stems, especially in marshes. Parasites of plants and other fungi are also found in the group.
Corticioid fungi have a worldwide distribution, but are obviously commonest in forest communities.