Stereaceae - Stereum

The orange colouration rescues these from obscurity, as does the fact that they usually project away from the surface and are not often fully resupinate. When scratched, they may stain/bleed red or yellow. The species are best separated microscopically, but can often be reliably identified by comparing how much they attach to the wood (single point, versus a line versus mostly resupinate), how bright or dull the orange colouration is on the underneath and whether or not it stains/bleeds yellow, red or neither when scratched.

Species mentioned: Stereum hirsutum, complicatum, ochraceoflavum, gausapatum, rugosum, subtomentosum, ostrea, sanguinolentum, atrorubrum

Stereum hirsutum EU - Most collections of Stereum are called this, because this species is the only one that most people know. It certainly is abundant, but many collections do end up being other species. It is mostly projecting from the wood, but broadly attached. The underside is bright orange, and the fruitbody is usually 1-2 mm thick. Like most, it is a hardwood species.

Western North American collections differ consistently from European sequences by the same single bp difference in ITS1 and the same 3 bp differences in ITS2 plus a large insertion of 8 bp. There may also be a few extra single indels. There is definitely some geographic isolation happening but I don't know that it's enough to consider ours a different species in need of a new name.

Stereum complicatum ENA? - Thinner than S. hirsutum (<0.5 mm), also brightly coloured and usually more wrinkled or complicated looking. It may have, as shown in this picture, a thin black zone between the majority of the cap that is orange and a white rim. It is commonly reported in the PNW but we have no genetic proof that those reports are correct. Although it is a Fries species, this appears to be one of those he had heard of from the Americas and therefore its type area is probably somewhere in the Americas. We have eastern NA sequences identified as this this species, but without a type designation or even a definitive type area, this is just an assumption for now. We need local collections.

Stereum hirsutum © Julie Jones, probable Stereum complicatum © James Hilliard

Stereum ochraceoflavum PN+FL - A hairy capped species with a very fringed edge, dull orange colours underneath when fresh (or browner, but never bright orange like S. hirsutum) and often found on smaller pieces of wood. We have 1 WA sequence and 2 OR sequences from Sarah DuLong-Duhon's Stereum study that reportedly match eastern NA sequences.

Stereum ochraceoflavum © iNaturalist user mnharris (2 images) and Michael Beug

Staining red when scratched ("red bleeders")

Stereum cf gausapatum EU - Usually capped but sometimes resupinate, only on oak, fairly bright orange, bleeding red when scratched. Stereum hirsutum can be on oak, but won't always be, and is also bright orange, but doesn't stain red. Our Vancouver Island and WA sequences matches sequences from eastern North America (with a handful of alleles or dirty sections being the only differences), but we don't have European sequences yet of this EU mushroom to see if our species is the real thing or a sister species.

Stereum cf rugosum EU - Pale ochre to pinkish-brownish instead of bright orange. Also a resupinate red bleeder on various hardwoods, rumoured to occur here. We need local collections to compare to European sequences to verify these reports, because the latest thinking is that this doesn't occur anywhere in North America, nevermind here.

Stereum sanguinolentum EU - A similar looking resupinate red bleeder, but dull tan-orange coloured on conifers. PNW and Eastern North American sequences match European sequences, so it is the same species worldwide.

Stereum atrorubrum BC (=S. subtomentosum EU?) - S. subtomentosum is mostly a cap, attached to the wood at a single point only, dull orange underneath, staining yellow-orange when scratched. On hardwoods. Local sequences are 3 bp and 2 indels different from EU sequences. However, the little known local species S. atrorubrum is thought to be an older synonym by Ryvardin and although nobody is disputing that (including me, since they are described from different parts of the world but the genetics match in both geographical areas), nobody is using the older name anyway. We need a type sequence and/or other local collections that specifically match S. atrorubrum to help prove this. For now, everybody is still using the newer name.

Stereum ostrea EU - identical, but bleeding red or yellow turning red. So far, sequences of this rarely reported species have all turned out to be other species, according to a recent study, so we need sequences of supposed collections to test the theory that all of ours are really just Stereum subtomentosum that happens to stain more towards the orange-red end of the spectrum instead of yellow.