Auricularia

The genus was first introduced in 1780 by French mycologist Pierre Bulliard for a range of different fungi producing fruit bodies with an ear-like shape. In 1822 Christian Hendrik Persoon restricted the genus to two gelatinous species, Auricularia mesenterica (which became the type species) and A. sambuci (a synonym of Auricularia auricula-judae).^[2] In 1848 Swedish mycologist Elias Magnus Fries accepted A. mesenterica within the genus but, on the basis of differences in fruitbody appearance, introduced a new genus, Hirneola, for most other species.^[3] This division into two genera was maintained by some authors until at least the 1960s,^[4] though American mycologist Bernard Lowy's monograph of the genus had accepted Hirneola as a synonym of Auricularia in 1952 .^[5]

Molecular research, based on cladistic analysis of DNA sequences, has shown that Auricularia (including Hirneola) forms a natural, monophyletic grouping. It has also shown that many species are more restricted in distribution than previously thought, resulting in the description of additional new taxa.^[6][7][8]

All species of Auricularia form thin, brownish, rubbery-gelatinous fruit bodies that are shelf-like or ear-shaped and up to 120 mm (4.7 in) across and 5 mm (0.20 in) thick. The fruitbodies occur singly or in clusters. The upper surface is finely pilose to densely hirsute. The spore-bearing underside is smooth, wrinkled, veined, or reticulate (net-like).^[8] Unpigmented white forms are occasionally encountered.^[9][10]

The spore-producing basidia are tubular, laterally septate, and (in some species) up to 100 μm long. The spores are allantoid (sausage-shaped), and (in some species) up to 22 μm long. Hairs on the upper surface are thick-walled, rounded or acute at the tip, and (in some species) up to 1 cm (0.39 in) long. When sectioned, some species show a central, medulla layer of parallel hyphae, others lack such a layer.^[8]

All species grow on wood and are saprotrophic wood-rotters, producing a white rot.^[11] Most occur on dead wood, but they can also be weakly parasitic on living wood. The majority of species grow on broadleaf trees and shrubs, but a few grow on conifers. Fruit bodies occur singly, in clusters, or in tiers.^[5][8]

The genus has a global distribution, with some species confined to the tropics, others to north temperate regions, and others to south temperate regions.^[5][8]