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Danny’s DNA Discoveries – Tricholomopsis of the PNW (Phyllotopsidaceae)
by Danny Miller

Click here for my Pictorial Key to Tricholomopsis


Beautiful mushrooms growing on wood that are bright reddish-purple and/or yellow and often scaly. They are small to medium sized white spored mushrooms. They are currently one of only two non-oyster gilled genera in the Phyllotopsidineae sub-order, the other being Aphroditeola which evolved an even more derived trait of  growing on the ground.

abundant common uncommon rare - colour codes match my Pictorial Key and are my opinions and probably reflect my bias of living in W WA. Rare species may be locally common in certain places at certain times.


Tricholomopsis 'rutilans PNW01' - nicknamed the "plums and custard" it is pinkish purple with black scales on both the cap and the stem. Bright yellow gills. No veil. Our half dozen or so sequences don't vary much from the EU type sequence in ITS, although there is a long chunk of indel that makes some of them look more different than they are. However, LSU is more different here than in the EU than ITS is, which is backwards from normal. An Olariaga paper suggests our species may deserve its own name (along with two other cryptic species in the EU), based solely on DNA, although they could not find any morphological or ecological differences.

Tricholomopsis 'flammula IN01' - more slender with black scales only on the cap. The stem is basically just yellow. No veil. It was never suspected to exist here until found through DNA, on the WA/ID border. It has since been found in the Seattle area too. It is 9 bp and 1 indel different than EU sequences, and probably needs its own name.

Tricholomopsis 'flammula PNW06' - a sister species, stockier but with the gestalt of IN01. Known from 2 WA collections and an IN collection.

Tricholomopsis 'rutilans PNW01' © Steve Trudell,     T. 'flammula IN01' © Andrew Parker,     T. 'flammula PNW06' © Yi-Min Wang


Tricholomopsis decora EU - pure yellow with blackish scales on the cap. No veil. ITS DNA matches 15/17 EU sequences and the concept chosen by at least one expert.

Tricholomopsis floccosa China - 2 BC sequences, one ID, and one OR sequence are 3% different. It is very similar and was finally described in 2023 and can be differentiated from T. decora by a wider stipe, darker cap, and coarser scales that are olive-brown (when fresh).

Tricholomopsis decora © Yi-Min Wang,     T. floccosa © Ed Barge and Heather Dawson (2 images)


Tricholomopsis sulfureoides NY  (=T. sulphureoides) - a yellow species where the cap scales are not black and with thin veil remnants on the stem. We have a sequence of what I think is an original Peck collection from NY and some matching AZ and WA sequences. var. megaspora from CA has larger spores.

Tricholomopsis sulfureoides © Andrew Parker


Tricholomopsis PNW04 - yellow, no black scales. One OR sequence clades by itself in a novel section outside all the others, perhaps this is one of the below species? It does stain yellow when bruised like T. fulvescens.

Tricholomopsis PNW05 - a single WA sequence may be Tricholomopsis fulvescens, or something else.

Tricholomopsis PNW04 © NAMA and the Field Museum of Natural History,     T. PNW05 © Noah Siegel


Please keep an eye out for any of the following species, none of which have local sequences nor type area sequences (if from a different area) and all are desperately in need of study. Save any Tricholomopsis that is somewhat yellow without black scales that might not be T. sulfureoides.

Tricholomopsis bella MI - yellow, staining brown where handled. No veil. One Smith report from Idaho in 1960.

Tricholomopsis flavissima WA - yellow marginate gills edges and a weak pale yellow partial veil. Reported more than once.

Tricholomopsis fulvescens WA - stem stains brownish-yellow, veil remnants left on stem. Reported in 1960 twice, from WA and OR.

Tricholomopsis glaucipes WA - olive grey cap and flesh, pale yellow stem, found once in 1960. I'm not convinced it's actually a Tricholomopsis.

Tricholomopsis resinosa WA - yellow cap with a resinous feel and brown scales, found once on the ground in 1960, so I'm not convinced it's actually a Tricholomopsis.

Tricholomopsis thomsponiana NY nom ill /flavescens NY - the only smooth yellow capped species, staining yellow where bruised. The Key Council key claims it might have been reported once in the PNW, but I have my doubts. The former name was illegally described and the latter name is probably the legal synonym.


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