Hymenochaetales

Taxonomy

History

The order was proposed in 1977 to recognize the family Hymenochaetaceae at a higher taxonomic rank. As originally conceived, species within the Hymenochaetales had several morphological features in common, notably brown or brownish basidiocarps (fruit bodies) that turn black in alkali, hyphae lacking clamp connections, and the presence (in most species) of characteristic setae (thick-walled, thorn-shaped cystidia, visible under a hand lens).

Subsequent ultrastructure research showed that the Hymenochaetales had dolipores with imperforate parenthesomes, whereas most Agaricomycetes have dolipores with perforate parenthesomes. Species of the corticioid genera Hyphodontia and Schizopora were later found to share this peculiarity, suggesting they might also be related to the Hymenochaetales, though morphologically dissimilar.

Current status

Molecular research, based on cladistic analysis of DNA sequences, has substantially expanded and redefined the Hymenochaetales, dividing the order into at least six different clades. The core clade represents the traditional Hymenochaetaceae, excluding the genera Coltricia and Coltriciella; another clade includes the corticioid genera Lyomyces and Schizopora (Schizoporaceae), together with Coltricia and Coltriciella as a subclade; a further clade (Repetobasidiaceae) includes agaricoid Rickenella species, the clavarioid Alloclavaria purpurea, and various corticioid fungi, including the genus Repetobasidium; the three remaining clades consist of corticioid Hyphodontia species, corticioid Kneifiella species, and poroid Oxyporus species.

Not all the species currently placed within the Hymenochaetales have dolipores with imperforate parenthosomes, so the order lacks any shared morphological characteristics.