Arrhenia s.l. - click to expand
There are two very distinct looks for Arrhenia, and some species
of the first type don't have strong support for belonging to this genus.
- small brown to dark brown (rarely greenish) omphalinoids on wood or moss (other
omphalinoids are not usually as dark brown, but consider
Omphalina itself for
yellow-brown, warm brown, or pinkish-red brown species on moss, and
Lichenomphalia below if the stem base has granular or leafy lichen
mateial).
- small dark brown
(rarely pale grey) "oysters" with eccentric/lateral/missing stems (but
growing on the ground in moss, not on wood) sometimes with poorly
developed gills. Rimbachia and Muscinupta,
both usually pure white unlike Arrhenia,
also may lack gills and grow on moss on the ground. Muscinupta
has a tapering fluted "stem".
Species mentioned:
Arrhenia acerosa, subglobisemen, lobata, auriscalpium, retiruga, chlorocyanea, epichysium, hohensis,
latispora, obscurata, onisca, peltigerina, pubescentipes,
rainierensis, sphagnicola.
My ITS only tree shows that Arrhenia, as well as
Lichenomphalia below, fall into 2 distinct clades far enough from each
other and it appears that a few of the species might need to be moved to
their own genus. In this case, a few of the omphalinoid Arrhenias
appear to be only distantly related to the others. I would like a multi-gene
study to verify this, as mine is not the only study to show that all
Arrhenias don't necessarily belong together. All oyster-like
Arrhenias belong in Arrhenia proper.
1. Moss associates with eccentric
stems and possibly poorly developed gills
These species don't
appear to all
group together (they may have gained or lost this shape in more than one
event) so we probably can't give them their own genus. We just have to accept that
there are two very distinct looks for Arrhenia. Similar looking
mushrooms are found in Rimbachia (Tricholomatineae) and Muscinupta
(Hymenochaetales), but those are pure white.
Arrhenia 'subglobisemen
PNW06' - brown, short lateral stem, fairly
well developed gills. It was reported that we have Arrhenia acerosa
EU here, but three sequences turn out to be 2% different than A.
subglobisemen instead and much further away from A. acerosa. If
anybody thinks A. acerosa is really here, save a collection because
we have EU DNA to compare to. It is a complex where ITS DNA can vary by 2%,
and has spores that vary widely in shape, often being almost round like in
A. subglobisemen, so that may have created the confusion, and if the
spore shape corresponds with certain ITS sequences in the complex, it could
also mean A. acerosa will be split up into more than one species.
Arrhenia cf. lobata EU - brown, stemless, poorly
developed wrinkle-like "gills". Reported from the PNW, and we
have EU DNA to compare to, but no collections to prove it's really here. We
need some, especially since it's similar to the previous species.
Arrhenia
'auriscalpium PNW07' - long lateral stem, slightly veined underside. One
North American sequence is 2% different than type area EU sequences. We
don't have local sequences (we need them) but ours is probably a sister
species and not the real thing.
Arrhenia 'retiruga PNW08' -
paler tan or grey felty cap, stemless, almost smooth underneath. One
WA sequence is 3% different than 2 competing concepts in the EU for what
this species is. Ours likely needs a new name.

Arrhenia 'subglobisemen PNW06' © Laruen Ré, A. 'auriscalpium
PNW07' © Ben Woo, A. 'retiruga PNW08' © NAMA and
the Field Museum of Natural History
2. Brown (rarely green) omphalinoid mushrooms
'Clitocybe' atroviridis WA (=Arrhenia
chlorocyanea EU?) - This unique, beautiful dark green
omphalinoid, found on the ground often in moss, was described from WA as
Clitocybe atroviridis but that is thought to be a synonym of the
older EU species Arrhenia chlorocyanea. We don't have any EU
sequences of that mushroom to compare to, and given that our local species
of other Arrhenias has turned out to be different than the EU
counterpart that was thought to be the same, we need EU sequences to find
out for sure. If not, we'll need to rename ours to Arrhenia
atroviridis.

unsequenced Arrhenia chlorocyanea © Ben Woo
'Arrhenia2' telmatiaea
UK (='Omphalina' fusconigra UK)
- recognizable by its dark brown smooth cap and growth in sphagnum.
It is in the "other" clade. Two OR sequences match the type sequence of this
newly described species. One theory is that Bigelow's reports of Arrhenia
onisca, which could not have been that species as it is a synonym of
Lichenomphalia umbellifera, represent A. telmatiaea.
'Arrhenia2' philonotis EU - a paler
brown smooth cap and growth in sphagnum. Also in the "other"
clade. Two OR sequences match the type sequence.

'Arrhenia2' telmatiaea and 'Arrhenia2' philonotus © Connor Dooley
'Arrhenia2'
bigelowii MI (=Arrhenia gerardiana var. fusca NY) - recognized by
having a scaly cap in sphagnum moss. One WA collection matches
the type sequence. Formerly, it was thought that this species/variety always
had a darker cap than Arrhenia gerardiana, but our local collection
confirms this is not the case. Dark capped collections are A. bigelowii.
Not-so-dark capped collections could be either A. bigelowii or A.
gerardiana (indistuingishable so far except for by DNA). Therefore,
local reports of A. gerardiana need confirmation as it is not yet
confirmed by DNA from the PNW. This is in the "other" clade of Arrhenia.

'Arrhenia2'
bigelowii © Luca Hickey
Arrhenia 'latispora PNW09' - a
moss species (not just sphagnum?) with wide spores (7.8-9.5 x 6.5u) and said to have a
geranium odor at least in the EU, where it was described. 2 collections from OR match the EU epitype
sequence, however the species is described as a pleurotoid oyster-like
mushroom, very different than what ours looks like. Stay tuned.
Arrhenia
'obscurata PNW11' - Arrhenia obscurata UK (=Omphalina
atrobrunnea UK) is found on sandy soil
or moss, reported from ID and BC. We don't have any UK sequences, but Voitk provides some ENA
sequences. Our one WA collection is at least 2% different in ITS. It's
possible ours will match true UK sequences of A. obscurata, but until we prove that, I'm giving it a code.

Arrhenia 'latispora PNW09' © Connor Dooley, and NAMA and the Field Museum of
Natural History, Arrhenia 'obscurata PNW11' ©
Matthew Koons
The following lookalike dark brown omphalinoid
species, from the ground or moss, are reported from here, and below
them I show four sequenced local collections that have not been matched up with anything specific
yet.
'Arrhenia2' epichysium EU - it should be investigated if
reports of this dark brown species on wood are really Arrhenia
telmatiaea, above, or something else. We need collections from wood
apart from sphagnum. We have some sequences of A.
epichysium from the EU to compare to. It's in the "other" clade.
Arrhenia cf peltigera NY - on Peltigera lichen. Bigelow
claims to have found this in Idaho, but we need local collections to
sequence to verify if it's really here. We don't even know what its DNA
looks like, the three east coast sequence that purport to be this are all
different sister species.
'Arrhenia onisca' EU -
Bigelow reported this from the PNW on moss or burned moss, but it's now
known that this name is a junior synonym of Lichenomphalia umbellifera,
so nobody knows what Bigelow really found. My leading theory is Arrhenia
telmatiaea, described above.
'Arrhenia sphagnicola' EU - This name too has officially been declared a
synonym of Lichenomphalia umbellifera, so it is no longer being used.
This name has been used for reports of A. bigelowii and A.
telmatiaea back when A. sphagnicola was incorrectly thought to be a synonym of
Omphalina gerardiana and O. fusconigra, but this name should not
be used anymore.
Arrhenia rainierensis WA
- on soil or moss with interesting shaped spores. Described from here but we
don't have any reliable sequences. I don't even know which clade it's in.
Arrhenia pubescentipes ID
- on soil or moss. No local sequences, so no idea which clade it's in.
'Arrhenia2'
hohensis WA - on soil or moss. Described from here but we have no
sequences. One mycologist suggested it might be similar to or the same as
the EU species Arrhenia obatra, if so, that species appears to be one
of those possibly needing to be moved to the new genus, so maybe A. hohensis
does too, but maybe not.
The first two ocal species below are in
the true Arrhenia clade. The last two are in the "other" clade.
They have slightly different 5.8s sequences than other Arrhenias, which is
unusual, but as I've seen it in more than one sequence, I think the
sequences are good.
Arrhenia PNW01 - 1 collection from OR
Arrhenia PNW10 - 2 collections from WA, in Polytrichum moss, with
a somewhat greasy cap with a wavy margin.
'Arrhenia2' PNW03 - a very dark, terrestrial
species not with moss. Found 3 times in WA so far.
'Arrhenia2'
PNW04 - 1 collection from WA
'Arrhenia2' PNW05 - on soil,
with highly contrasting colour striations on the cap. 1 collection
from OR.

Arrhenia PNW01 OR © Bitty Roy, Arrhenia PNW10 ©
iNaturalist user fish_narc (2 images)
'Arrhenia2'
PNW03 and PNW04 © Yi-Min Wang, 'Arrhenia2' PNW05 ©
Connor Dooley