ArticlePDF Available

Surprising morphological, ecological and ITS sequence diversity in the Arrhenia acerosa complex (Basidiomycota: Agaricales: Hygrophoraceae)

Authors:

Abstract and Figures

A molecular genetic study of the Arrhenia acerosa complex using the ITS fungal barcoding marker revealed unexpected diversity along a cascading group supporting over 20 lineages. Among these, we identified five previously described species: A. acerosa s.str., A. glauca, A. latispora, A. subglobisemen, and Rhodocybe tillii (recombined as A. tillii). We described four new species: A. fenicola from Canadian prairie grasslands, A. juncorum and A. leucotricha, both on live and dead herbaceous material in European wetlands, and A. svalbardensis from the high Arctic. All nine taxa treated here were fixed with sequenced types. In addition, we identified seven other lineages, some only represented by a single collection, requiring further study before description, and four groups of two species or more, also requiring further dissection before circumscription of their constituents. The diversity of the complex with respect to size, colour, habitat, range, distribution, and substrate preference is made more intriguing by the presence of several lineages of brown omphalinoid species, differing from the typically pleurotoid forms in this complex. We generated 97 of the 131 ITS sequences studied, adding 65 new sequences from the acerosa complex.
Content may be subject to copyright.
Sydowia 73 (2021) 133
DOI 10.12905/0380.sydowia73-2020-0133 Published online 11 December 2020
Surprising morphological, ecological and ITS sequence
diversity in the
Arrhenia acerosa
complex (Basidiomy-
cota: Agaricales: Hygrophoraceae)
Andrus Voitk1,*, Irja Saar2, Robert Lücking3, Pierre-Arthur Moreau4, Gilles Corriol5,
Irmgard Krisai-Greilhuber6, R. Greg Thorn7, Chris R. J. Hay8, Bibiana Moncada9 & Gro Gulden10
1 ORCID 0000-0002-3483-8325, Foray Newfoundland & Labrador, 13 Maple St, Humber Village, NL, Canada, A2H 2N2
2 ORCID 0000-0001-8453-9721, Institute of Ecology and Earth Sciences, University of Tartu, Ravila St. 14A, 50411 Tartu,
Estonia
3 ORCID 0000-0002-3431-4636, Botanischer Garten und Botanisches Museum, Freie Universität Berlin,
Königin-Luise-Strasse 6–8, 14195 Berlin, Germany
4 Université de Lille, ULR 4515, Laboratoire de Génie Civil et géo-Environnement (LGCgE), Faculté de pharmacie,
59000 Lille, France
5 Conservatoire botanique national des Pyrénées et de Midi-Pyrénées, Vallon de Salut, BP 70315,
65203 Bagnères-de-Bigorre Cedex, France
6 ORCID 0000-0003-1078-3080, Department of Botany and Biodiversity Research, Universität Wien, Rennweg 14,
1030 Wien, Austria
7 ORCID 0000-0002-7199-6226, Department of Biology, University of Western Ontario, 1151 Richmond St. N.,
London, ON N6A 5B7, Canada.
8 Department of Biology, University of Western Ontario, 1151 Richmond St. N., London, ON N6A 5B7, Canada.
9 ORCID 0000-0001-9984-2918, Licenciatura en Biología, Universidad Distrital Francisco José de Caldas, Cra. 4 No. 26D-54,
Torre de Laboratorios, Herbario, Bogotá D.C., Colombia; Research Associate, Integrative Research Center, The Field Museum,
1400 South Lake Shore, Chicago, IL 60605, USA.
10 Natural History Museum, University of Oslo, PO Box 1172 Blindern, NO-0318 Oslo, Norway
* e-mail: seened@gmail.com
Voitk A., Saar I., Lücking R., Moreau P.-A., Corriol G., Krisai-Greilhuber I., Thorn R.G., Hay C.R.J., Moncada B. & Gulden G.
(2020) Surprising morphological, ecological and ITS sequence diversity in the Arrhenia acerosa complex (Basidiomycota: Agari-
cales: Hygrophoraceae) – Sydowia 73: 133–162.
A molecular genetic study of the Arrhenia acerosa complex using the ITS fungal barcoding marker revealed unexpected di-
versity along a cascading group supporting over 20 lineages. Among these, we identied ve previously described species: A.
acerosa s.str., A. glauca, A. latispora, A. subglobisemen, and Rhodocybe tillii (recombined as A. tillii). We described four new spe-
cies: A. fenicola from Canadian prairie grasslands, A. juncorum and A. leucotricha, both on live and dead herbaceous material in
European wetlands, and A. svalbardensis from the high Arctic. All nine taxa treated here were xed with sequenced types. In
addition, we identied seven other lineages, some only represented by a single collection, requiring further study before descrip-
tion, and four groups of two species or more, also requiring further dissection before circumscription of their constituents. The
diversity of the complex with respect to size, colour, habitat, range, distribution, and substrate preference is made more intrigu-
ing by the presence of several lineages of brown omphalinoid species, differing from the typically pleurotoid forms in this com-
plex. We generated 97 of the 131 ITS sequences studied, adding 65 new sequences from the acerosa complex.
Keywords: ITS, pleurotoid basidiomycota, taxonomy. – 4 new species, 9 typications.
In the course of a review of the genus Arrhenia
Fr. in the Canadian province of Newfoundland and
Labrador, we noted that the species we had consist-
ently identied as Arrhenia acerosa (Fr.) Kühner
formed a sister clade with the only collection bear-
ing the same name available in GenBank at the time
(Geml et al. 2012b). In an attempt to identify the
species in Newfoundland and dene the application
of the name A. acerosa, a broader sampling of this
complex, particularly from North and Central Eu-
rope, was undertaken.
For a long time Arrhenia, introduced by Fries
(1849), was considered a small genus of mostly moss
associates producing small dorsally attached or
pleurotoid basidiomata with a reduced hymenium,
ranging from smooth to veined with low, sinuous,
anastomosing folds, similar to its type species, A.
auriscalpium (Kühner & Lamoure 1972). Two of the
134 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
three taxa initially included in Arrhenia were later
transferred to other genera. Species morphologi-
cally similar to Arrhenia sensu Fries but with dis-
tinct lamellae were assigned to the genus Phaeotel-
lus Kühner & Lamoure, with Agaricus acerosus Fr.,
rst described in 1821 (Fries 1821), as type species
(Kühner & Lamoure 1972). Subsequently Kühner
(1980) merged both genera under Arrhenia, thereby
making A. acerosa the rst species in the genus with
distinct lamellae. Bon & Courtecuisse (1987) added
two other lamellate species, A. glauca (Batsch) Bon
& Courtec. and A. latispora (J. Favre) Bon & Cour-
tec., and Watling (1989) assigned A. griseopallida
(Desm.) Watling and A. rickenii (Hora) Watling, the
rst two omphalinoid species, to this genus. Later,
additional omphalinoid species were transferred to
Arrhenia by Redhead et al. (2002), followed by oth-
ers, e.g. Moreau & Courtecuisse (Courtecuisse 2008)
and Elborne (2008). The diverse phenotypes includ-
ed in the thus emended genus Arrhenia formed a
coherent, yet paraphyletic assemblage with pleuro-
toid and omphalinoid phenotypes occurring in vari-
ous lineages without forming reciprocally mono-
phyletic clades, eventually leading to the lichenized
Dictyonema C. Agardh and related basidiolichens
(Lawrey et al. 2009, Lodge et al. 2014). Initially in-
cluded in Pleurotaceae (Kühner & Lamoure 1972)
and Tricholomataceae (Kühner 1980), Arrhenia was
found to be closer to Omphalina Quél. and Hy-
grophoraceae (Lutzoni 1997, Moncalvo et al. 2002),
subsequently conrmed by more detailed phyloge-
netic studies (Lawrey et al. 2009, Lodge et al. 2014).
So far, no broad-scale phylogenetic analysis of Ar-
rhenia s.l. has been undertaken, and hence the
placement of individual lineages, such as A. acerosa
and relatives, remains unknown.
Over 50 years after describing the species, Fries
(1874a, b) considered Agaricus acerosus “maxime
variabilis” and nearly a century after that Kühner &
Lamoure (1972) suggested that Phaeotellus aceros-
us might be a collective species. Several taxa simi-
lar to A. acerosa have been described over the years,
and a study of the group by molecular genetic meth-
ods seems overdue. We shall refer to the group as
“the acerosa complex”, dened for the purposes of
this phylogenetic study to mean species arising
from the nearest monophyletic lineage that encom-
passes all taxa morphologically resembling A. ace-
rosa. A brief review of epithets applied to this group,
in order of publication, follows.
Schäffer (1774) described Agaricus tremulus
Schaeff., a gelatinous-leathery and abellate spe-
cies; the name has been applied for generations to
an acerosa-like species as Pleurotellus tremulus
(Schaeff.) Konrad & Maubl. Redhead (1984) reject-
ed P. tremulus as a separate species, pointing out
that none of its identifying characters were unique,
due to the range of morphological variation of A.
acerosa, and argued that its protologue ts better
with a species of Hohenbuehelia Schulzer. The name
has since been applied to a species of Hohenbuehe-
lia (Thorn & Barron 1986) and recently epitypied
as such (Consiglio 2016), making it unavailable for
an Arrhenia.
Batsch (1786) described Agaricus glaucus Batsch
from the Webicht woods near Weimar, Germany.
Fries (1874a, b) referred it to Cantharellus, starting
it on a circuitous journey before reaching Arrhenia
as a separate species (Bon & Courtecuisse 1987).
Most experts have synonymized it with A. acerosa
(Redhead 1984, Kuyper 1995, Barrasa & Rico 2003),
but Pilát & Svrcˇek (1953) provided a personal inter-
pretation of this name based on a collection from
the Czech steppes.
The epithet planus has been applied to taxa in
this group at the form, variety and species level for
both pink and non-pink basidiomata. It was rst
described and illustrated by Bolton (1788) for a
non-pink terricolous species, Ag. planus. Persoon
(1801) used it twice in his Synopsis, rst on p. 480
referring to his earlier description (Persoon 1796) of
the non-pink Ag. applanatus Pers. This makes Ag.
planus Pers. illegitimate, rst because of its earlier
use by Bolton for a different taxon, and second, be-
cause Persoon introduced it as a superuous name
for the brown-spored species currently known as
Crepidotus applanatus (Pers.) P. Kumm. Persoon
used planus a second time on p. 484, where he listed
it as a (presumably non-pink) variety of the pink
Ag. depluens Batsch, this time citing Bolton’s non-
pink description. Von Albertini & von Schweinitz
(1805) described a pink acerosa-like taxon, Ag.
planus var. violaceo-ruber Alb. & Schwein., as a va-
riety of Ag. planus Pers., but when Fries (1828) de-
scribed Ag. planus Fr., he based the description on
the variety established by von Albertini and von
Schweinitz, and specically excluded the invalid
and superuous Persoon name. Because Fries’ name
is considered sanctioned, it has priority over all ear-
lier applications of the epithet “planus” in the genus
Agaricus, making Ag. planus the correct name, now
at the species level, for the pink variety described
by von Albertini and von Schweinitz. Subsequently
the species was transferred to Pleurotus by Kum-
mer (1871). In his monograph of Pleurotus, Pilat
(1935) reclassied P. planus va r. violaceo-ruber (Alb.
& Schwein.) Kumm. as a pink form of P. acerosus,
differing from the autonymic form by its pink col-
Sydowia 73 (2021) 135
Voitk et al.: The Arrhenia acerosa complex
our only. Hesler (1967) placed the non-pink Ag.
planus Bolton and the pink Ag. planus var. viola-
ceo-ruber Alb. & Schwein. in synonymy with Ento-
loma depluens (Batsch) Hesler. The epithet planus
has not been transferred to Arrhenia at the species,
form, or variety level for either pink or non-pink
basidiomata.
Agaricus acerosus was described by Fries (1821)
as a small mushroom with a short eccentric stipe,
growing among woody debris in dense coniferous
forests. Since then the species has been reported
from various habitats and assigned to no less than
eight genera, including Kühner’s (1980) transfer to
its current genus, Arrhenia.
Quélet (Le Breton & Quélet “1879” 1880) de-
scribed Pleurotus roseolus as a small conchate pink
fungus with a relatively prominent near-central
stipe and white sporeprint, growing on Juncus or
Gramineae. Senn-Irlet (1986) transferred P. roseo-
lus Quél. to Arrhenia. Quélet’s protologue, together
with an illustration matching Deconica phillipsii
(Berk. & Broome) Noordel. lead us to conclude that
roseola is misapplied to a pink-spored species of
Arrhenia, and is a later synonym for Agaricus phil-
lipsii Berk. & Broome.
While Ag. acerosus was classied in Pleurotellus
Fayod, on the basis of three separate collections Küh-
ner (1954) described a variety, Pleurotellus acerosus
var. tenellus Kühner, which differs by having
2-spored (instead of 4-spored) basidia and larger
spores. This variety was transferred to Arrhenia
(Aronsen 1992). Barrasa & Rico (2003) designated
Kühner’s rst collection (from Algiers) as lectotype
for the variety, but thought that more observations
were required of it, before deciding to elevate the va-
riety to species level, noting a small amount of 1-, 3-
and 4-spored basidia in 2-spored collections, as had
been reported by Kühner & Lamoure (1972) and Gul-
den & Jenssen (1988). The variety was recently raised
to species level (Blanco-Dios 2019) as A. kuehneri,
the epithet “tenella” being occupied in Arrhenia.
Favre (1955) described Pleurotellus acerosus f.
latisporus, differing from P. acerosus by broader
spores. Redhead (1984) placed Favre’s form (and by
extension the derived varietal and specic taxon) in
synonymy with the nominal variety, noting spore
size of A. acerosa is “extremely variable”. Preferring
to consider it a separate entity, Bon & Courtecuisse
(1987) transferred the taxon to Arrhenia, elevating
it to species level. Barrasa & Rico (2003) reported
that the wide amplitude of spore width for A. acer-
osa did not warrant maintaining a separate variety
by this character alone, and synonymized A. acerosa
var. latispora with A. acerosa var. acerosa.
Since the description of Rhodocybe/Clitopilus
tillii (Krisai-Greilhuber & Noordeloos 1998, Co-
David et al. 2009), some collections initially identi-
ed as Arrhenia roseola have been referred to that
taxon, but the relationship between the two, and
other pink acerosa-like collections, has not been
clear.
Corriol (2016) described Arrhenia subglobise-
men Corriol, which differs from A. acerosa by sub-
globose spores and more orid lobulation, often
producing multicephalic basidiomata in advanced
maturity. In his opinion, this is the species previ-
ously identied with the name Pleurotellus tremu-
lus. A year after publication, the species was also
reported from Newfoundland (Voitk 2017).
In addition to the foregoing, among taxa de-
scribed in Pleurotus that may be species of the ace-
rosa complex but have not been investigated, are P.
rivulorum Pat. & Doass. (Doassans & Patouillard
1886) from France, and several from Eastern Eu-
rope, described by Velenovský [e.g. P. diabasicus Vel.,
P. terrestris Vel., P. viaticus Vel. (Velenovský 1920), P.
thuidii Vel. (Velenovský 1927)] and by Pilát [e.g. P.
arbuticola Pilát, invalidly published without Latin
diagnosis, but validated as Phaeotellus arbuticola
Pilát ex Bon (Bon & Chevassut 1988) and P. romel-
lianus Pilát (Pilát 1935)]. Further, Corriol’s (2016)
key to A. acerosa-like species in Europe included
Gerronema josserandii Singer and Arrhenia subglo-
bispora (Moreno, Heykoop & Horak) Redhead, Lu-
zoni, Moncalvo & Vilgalys.
Given this complex situation, we aimed to i)
identify the species in Newfoundland and Labra-
dor, ii) x the name A. acerosa by typication, iii)
clarify the phylogenetic relationship of the taxa in
the acerosa complex, specically including A. acer-
osa, A. glauca, A. latispora, A. subglobisemen, and
A. acerosa var. tenella, and iv) explore the relation-
ship of A. subglobispora, Gerronema josserandii,
and Rhodocybe/Clitopilus tillii to this group.
Materials and methods
Specimens were collected using routine eld
techniques and air dried with heat <40 °C. To these
were added specimens from public herbaria in Aus-
tria (WU), Canada (CMMF, DAOM, SWGC, UW), Es-
tonia (TAAM, TU), France (BBF, LIP), Norway (O),
Sweden (GB, UPS), and Switzerland (G), private
collections of the authors, and selected additional
collections. Herbaria are designated with the Index
Herbariorum code (Thiers 2020). To examine the re-
lationship of taxa considered similar to A. acerosa,
we include the type of Rhodocybe tillii, one pink
136 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
collection identied as Arrhenia roseola, one speci-
men identied as Arrhenia subglobispora and one
as Gerronema josserandii. In addition, both new
and existing sequences from other species of Arrhe-
nia are used to clarify the place of the acerosa com-
plex within the genus. Table 1 summarizes data of
collections used for this study, with more complete
details recorded in Supplemental Tab. 1. New se-
quences were deposited in GenBank or UNITE.
Macroscopic descriptions are based on in situ
specimens. Colour was matched from Cailleux
(1981) for A. acerosa and A. svalbardensis, Munsell
Soil Color Charts (Munsell Color Co 2000) for A.
subglobisemen, and Kornerup & Wanscher (1978)
for A. fenicola and A. glauca. Microscopic examina-
tion was done on squash mounts in 2–5 % KOH of
both live and dried specimens; Cotton blue in lactic
acid and Melzer’s Reagent were used to examine
slides of A. acerosa s. str. and A. svalbardensis.
Spore sizes reported in the descriptions are from
multiple observers. The WU spore measurements
were done with a Zeiss Axio Imager.A1 compound
microscope with Nomarski differential interference
contrast (DIC) using a Zeiss Axiocam 506 colour
digital camera and Zeiss ZEN Blue Edition soft-
ware. Microscopic examination and spore measure-
ments of the Pyrenean collection of A. subglobise-
men followed the procedure of Corriol (2016), that
for the Scandinavian collections followed Gulden
(1980) and microscopy of the ON and NL collec-
tions followed Thorn et al. (2017).
To construct the phylogeny, all available related
sequences deposited in GenBank and UNITE (Kõl-
jalg et al. 2013, Nilsson et al. 2019) were added to
the analysis. Because there was no extant type ma-
terial for A. acerosa, a similar specimen from the
toporegion with similar habitat and substrate as
described in the protologue, is proposed below as
neotype. Types for both A. latispora and A. subglo-
bisemen were not available for destructive sam-
pling, so that a sequenced epitype for each is pro-
posed. ITS-DNA processing of specimens deposited
in UNITE (with UDB- code) followed Voitk et al.
(2017); the WU specimens followed Hahn et al.
(2018); all A. obscurata specimens in Fig. 1a except
TU117230, as well as specimens numbered 10 and
13 in Fig 1b, followed the technique described in
Lücking et al. (2017).
For the purpose of discussion, we assign a code
name AC-n to identify undescribed potential spe-
cies in the acerosa complex. AC stands for acerosa
complex and n is a number assigned in consecutive
order as these groups appear in our phylogenetic
tree (Fig. 1b), starting at the top. Specimens not cir-
cumscribable as species were placed in larger
groups, which probably contain more than one spe-
cies, coded G-n.
Results
We generated the only available sequence of the
fungal ITS barcoding marker for a specimen identi-
ed as Gerronema josserandii and 86 new sequenc-
es for species of Arrhenia (Figs 1a & b; two not
shown in our tree), including several species not se-
quenced previously (indicated by an asterisk on
rst mention). Included species of Arrhenia (Fig. 1a)
form three larger, supported clades. The rst com-
prises taxa identied as A. epichysium, A. ve-
lutipes*, A. sphagnicola and A. philonotis and is a
strongly supported sister to a clade including all
other species. The second well-supported clade, in a
supported sister group relationship with the third,
encompasses species identied as A. auriscalpium,
A. salina*, A. lobata, A. peltigerina*, A. elegans, A.
retiruga and A. spathulata*. The third clade con-
sists of two sister pathways, one leading to speci-
mens identied as A. obscurata and the other to the
acerosa complex (Fig. 1b), a long cascading clade of
several well-supported clades.
The acerosa complex contains collections from
Asia, Europe and North and South America, origi-
nally identied as A. acerosa, A. acerosa va r. tenella,
A. latispora (A. acerosa va r. latispora), A. roseola, A.
subglobisemen, Rhodocybe (Clitopilus) tillii and A.
(Phaeotellus) griseopallida(-us). Habitats varied
from harsh arctic-alpine to woodland, meadow,
prairie, wetland, and littoral sand dune, and sub-
strates varied from soil, wood, bryophytes, live and
dead herbaceous material and herbivore dung. Both
plesiomorphic and convergent homoplasy is evident
in the different subclades of the complex. Basidio-
mata with 4- and 2-spored basidia, pink, brown,
grey or dark violet colour, pink or white sporeprint,
wide to narrow spores, and pleurotoid (with or
without signicant stipe formation) to omphalinoid
habitat are distributed throughout. Fig. 1b summa-
rizes available characters for these collections, and
Figs. 2–5 give an overview of the morphologic diver-
sity of the group.
As the phylogenetic tree grew with each addi-
tion of sequences during the investigation, several
well-supported clades appeared. Often additions or
different outgroups caused changes in the position
of these clades in the tree, but their support and
composition remained constant. We recognize ve
such clades as previously described species, four as
new species described here, nine as potential addi-
Sydowia 73 (2021) 137
Voitk et al.: The Arrhenia acerosa complex
Tab. 1. Data of collections and specimens used in this study.
Species Herbarium vouchera,
copy or strain
Country,
Prov/State
CODE:
GB (above)
UNITE (below)
Reference
Arrhenia epichysium LE-262961 Russia KC237880 Zviagina et al. (2015)
Arrhenia epichysium WU-21938 Austria MW113695 this study
Arrhenia epichysium
(as Omphalina epichysium)
Redhead 5223 Canada U66442 Lutzoni (1997)
Arrhenia epichysium 17148 Finland JF908504 Osmundson et al. (2013)
Arrhenia velutipes WU-28855 Austria MW113696 this study
Arrhenia velutipes WU-22371 Austria MW113697 this study
Arrhenia sphagnicola
(as Omphalina sphagnicola)
Lutzoni 930810-1,
DUKE
Greenland U66453 Lutzoni (1997)
Arrhenia philonotis
(as Omphalina philonotis)
Lutzoni 930804-5,
DUKE & O
Iceland U66449 Lutzoni (1997)
Arrhenia philonotis DAOM-744401 Canada, NL MH491521 Lickey et al.b
Arrhenia philonotis DAOM-744400 Canada, NL MH491520 Lickey et al.b
Arrhenia auriscalpium Lutzoni 930731-3,
DUKE & O
Iceland U66428 Lutzoni (1997)
Arrhenia sp. environmental sample Canada, NT KF296806 Timling et al. (2014)
Arrhenia salina O-260200 Norway, Svalbard MT967341
UDB024594
this study
Arrhenia lobata O-73053 Norway, Svalbard GU234033 Geml et al. (2012b)
Arrhenia lobata WU-38079 Austria MW113698 this study
Arrhenia lobata Lutzoni & Lamoure
910824-1, DUKE
France U66429 Lutzoni (1997)
Arrhenia lobata DAOM-981256
(TU-117633)
Canada, NL MT967332
UDB034988
this study
Arrhenia peltigerina DAOM-981257
(TU-117595)
Canada, NL MT967339
UDB034636
this study
Arrhenia peltigerina TU-111507 Estonia MT967334
UDB034594
this study
Arrhenia peltigerina DAOM-981258
(TU-117465)
Canada, NL MT967337
UDB032197
this study
Arrhenia peltigerina DAOM-981259
(TU-117594)
Canada, NL MT967338
UDB034635
this study
Arrhenia peltigerina DAOM-981260
(TU-117461)
Canada, NL MT967335
UDB032195
this study
Arrhenia peltigerina DAOM-981261
(TU-117462)
Canada, NL MT967336
UDB032196
this study
Arrhenia elegans WU-36410 Austria MW113699 this study
Arrhenia subglobispora BSI 14/8 Switzerland KR606032 Senn-Irletc
Arrhenia elegans MCVE-16455 Italy JF908757 Osmundson et al. (2013)
Arrhenia retirugis GB-0150441 Sweden EU118604 Larsson (2007)
Arrhenia retiruga TU-117227 Estonia MT967340
UDB024164
this study
Arrhenia spathulata TU-105605 Estonia MT967347
UDB024678
this study
Arrhenia spathulata TAAM-172613 Estonia MT967343
UDB024233
this study
138 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
Species Herbarium vouchera,
copy or strain
Country,
Prov/State
CODE:
GB (above)
UNITE (below)
Reference
Arrhenia spathulata WU-25434 Austria MW113700 this study
Arrhenia spathulata TAAM-172614 Estonia MT967344
UDB024232
this study
Arrhenia spathulata WU-38990 Austria MW113701 this study
Arrhenia spathulata TU-105606 Estonia MT967348
UDB024321
this study
Arrhenia spathulata TAAM-185757 Estonia MT967346
UDB031174
this study
Arrhenia spathulata TAAM-182905 Estonia MT967345
UDB024234
this study
Arrhenia spathulata TAAM-172553 Estonia MT967342
UDB024231
this study
Arrhenia obscurata
(as Omphalina obscurata)
Lutzoni & Lamoure
L73-101, polyspore
culture
France U66448 Lutzoni (1997)
Arrhenia obscurata nonedCanada, NL MT998928 this study
Arrhenia obscurata nonedCanada, NL MT998930 this study
Arrhenia obscurata nonedCanada, NL MT998929 this study
Arrhenia obscurata TU-117230 Canada, NL MT967333
UDB024573
this study
Arrhenia obscurata nonedCanada, NL MT998927 this study
Arrhenia obscurata nonedCanada, NL MT998924 this study
Arrhenia obscurata nonedCanada, NL MT998925 this study
Arrhenia obscurata nonedCanada, NL MT998923 this study
Arrhenia subglobispora BBF-JF03212 France UDB033389 this study; not in tree
Gerronema josserandii BBF-GC15091302 France UDB035029 this study; not in tree
Arrhenia latispora WU-22359 Austria MW113702 this study
Arrhenia latispora BBF-GC01082301 France MT967323
UDB033386
this study
Arrhenia latispora EPITYPUS LIP-0401569 France MT967324
UDB033395
this study
AC-1 O-63232 Norway MT967299
UDB032089
this study
AC-1 O-67900 Norway MT967301
UDB032091
this study
Arrhenia subglobisemen DAOM-981251
(TU-117353)
Canada, NL MT967351
UDB032180
this study
Arrhenia subglobisemen DAOM-981254
(TU-117355)
Canada, NL MT967353
UDB032184
this study
Arrhenia subglobisemen O-291235 Norway MT967350
UDB032092
this study
Arrhenia subglobisemen DAOM-981253
(TU-117464)
Canada, NL MT967354
UDB032725
this study
Arrhenia subglobisemen nonedCanada, NL MT998926 this study
Arrhenia subglobisemen DAOM-981252
(TU-117354)
Canada, NL MT967352
UDB032181
this study
Sydowia 73 (2021) 139
Voitk et al.: The Arrhenia acerosa complex
Species Herbarium vouchera,
copy or strain
Country,
Prov/State
CODE:
GB (above)
UNITE (below)
Reference
Arrhenia subglobisemen EPITYUS BBF-GC15100901 France MT967349
UDB033382
this study
Arrhenia subglobisemen DAOM-981255 Canada, NL MT998922 this study
Arrhenia subglobisemen TU-120029 Estonia MT967355
UDB023709
this study
AC-2 TU-120494 Estonia MT967307
UDB031497
this study
Arrhenia tillii HOLOTYPUS WU-18120 Austria MT967360
UDB039744
this study
AC-3 BBF-GC13082701 France MT967294
UDB033385
this study
G-1 environmental sample Lithuania MT237088 Marciulynas et al. (2020)
G-1 WU-8395 Austria MT967309
UDB039750
this study
G-1 BBF-GC08101503 France MT967293
UDB033390
this study
G-1 LIP-0401689 Spain MT952839 this study
G-1 BBF-GC08090407 France MT967292/
UDB033391
this study
G-1 BBF-GC13082806 France MT967295
UDB033384
this study
G-1 WU-12194 Netherlands MT967308
UDB039751
this study
G-1 O-65097 Norway MT967300
UDB024591
this study
G-1 LDhSweden MT967303
UDB038351
this study
G-2 TENN-074409 USA, TN MH558290 Matheny et al.c
G-2 HUH-11394
(TU-117356)
USA, NH MT967306e
UDB032183
this study
G-2 HUH-11394
(TU-117203)
USA, NH MT967305e
UDB024572
this study
G-2 environmental sample USA, NY JX030244 Tourtellot et al.c
G-2 WU-25862 Austria MW113703 this study
G-2 QFB-32684 Canada, QC MW057244 Landryf
G-2 TU-109664 Estonia MT967304
UDB024225
this study
G-2 CORD-X
(FLAS-F-64782)
Argentina KY462678 Truong et al. (2017)
G-2 environmental sample China MK342048 Guo et al.c
Arrhenia fenicola environmental sample Canada, AB MG417815 Thompson et al.b
Arrhenia fenicola environmental sample Canada, AB MG433164 Thompson et al.b
Arrhenia fenicola HOLOTYPUS UWO-F44 (HA10) Canada, ON KY706173 this study
Arrhenia glauca EPITYPUS WU-6564 Austria MT967319
UDB039746
this study
Arrhenia glauca O-64979 Norway MT967318
UDB024590
this study
140 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
Species Herbarium vouchera,
copy or strain
Country,
Prov/State
CODE:
GB (above)
UNITE (below)
Reference
Arrhenia glauca O-189477 Norway MT967317
UDB032088
this study
Arrhenia glauca LIP-0401688 France MT952840 this study
Arrhenia glauca Lueck2 Germany KP965766 Karich et al. (2015)
Arrhenia glauca GB-0058858 Sweden MT967316
UDB032047
this study
Arrhenia glauca BBF-GC97092813 France MT967313
UDB033388
this study
Arrhenia glauca GB-0017687 Sweden MT967314
UDB032046
this study
Arrhenia glauca GB-0058855 Sweden MT967315
UDB032045
this study
Arrhenia glauca WU-9855 Austria MT967320
UDB039749
this study
G-3 WU-25471 Austria MW113704 this study
G-3 environmental sample Austria FJ237148 Kuhnert et al. (2012)
G-3 G-00295825 France MT967297
UDB032043
this study
G-3 environmental sample USA, CO MK719126 Bueno de Mesquita et al.
(2020)
G-3 environmental sample USA, CO MH238865 Bueno de Mesquita et al.
(2018)
G-3 environmental sample Austria EF635806 Oberkoer & Peintner
(2008)
G-3 WU-32560 Austria MW113705 this study
Arrhenia acerosa TU-109632 Estonia MT967311
UDB024210
this study
Arrhenia acerosa O-189467 Norway MT967310
UDB032087
this study
Arrhenia acerosa NEOTYPUS UPS-F151993 Sweden MT967312
UDB032044
this study
AC- 4 LDhSweden MT967302
UDB038352
this study
Arrhenia juncorum BBF-CH13091225 France MT967321
UDB033383
this study
Arrhenia juncorum HOLOTYPUS LIP-0401674 France MT967322
UDB033394
this study
AC-5 CMMF-003682 Canada, QC MT967296
UDB035025
this study
AC-6 environmental sample Canada, NT KF296989 Timling et al. (2014)
AC-7 environmental sample Canada, BC KP889745 Guichon & Simardc
Arrhenia svalbardensis O-195466 Norway, Svalbard GU234048gGeml et al. (2012b)
Arrhenia svalbardensis HOLOTY-
PUS
O-50446 Norway, Svalbard MT967358
UDB024589
this study
Arrhenia svalbardensis O-195466 Norway, Svalbard MT967356g
UDB024587
this study
Sydowia 73 (2021) 141
Voitk et al.: The Arrhenia acerosa complex
tional species, codenamed AC-1–AC-9, and four
groups of unresolved species, designated G-1–4,
probably containing more than one species, where
ITS data seemed insufcient to determine species
limits with reasonable condence.
Previously recognized species (in order of rst
description; more complete treatment under Taxon-
omy). When Batsch described Agaricus glaucus
(Batsch 1786) he did not indicate a type but provided
an illustration (Fig. 2C), which we designate below
as lectotype. Collection WU-6564 (Fig. 2B) is a per-
fect match for this lectotype, and ts the description
in Batsch’s protologue. It comes from a similar cen-
tral European woodland habitat, about 400 km from
the type location. Below we designate this collection
as epitype for the species. It belongs in a large clade
with collections from Scandinavia and central Eu-
rope, which has enjoyed consistently high support in
all our phylogenetic analyses. Agaricus acerosus Fr.,
s. str.* (Fig. 2A), is neotypied below by a collection
(UPS-151993) from Femsjö, the type locality, tting
Fries’ protologue morphologically, growing on
woody debris in similar forest habitat. It was one of
three collections from northern Europe, which
formed a clade with consistently high support in all
our phylogenetic analyses. Three collections of A.
Species Herbarium vouchera,
copy or strain
Country,
Prov/State
CODE:
GB (above)
UNITE (below)
Reference
Arrhenia svalbardensis O-50444 Norway, Svalbard MT967357
UDB024592
this study
Arrhenia svalbardensis environmental sample Canada, NT KC966345 Timling et al. (2014)
Arrhenia svalbardensis O-76070 Norway, Svalbard MT967359
UDB024593
this study
AC-8 GB-0202287 Sweden, Lapland MT994562 Ellen Larssonf
AC-9 Lutzoni & Lamoure
910824-4, DUKE
France U66436
(as Phaeotellus
griseopallidus)
Lutzoni (1997)
AC-9 O-50445 Norway, Svalbard MT967298
UDB024588
this study
Arrhenia leucotricha WU-6774 Austria MT967331
UDB039747
this study
Arrhenia leucotricha
HOLOTYPUS
LIP-0401673 France MT967329
UDB033396
this study
Arrhenia leucotricha BBF-GC98092305 France MT967328
UDB033387
this study
Arrhenia leucotricha BBF-GC03091814 France MT967327
UDB033392
this study
Arrhenia leucotricha BBF-CH13091220 France MT967325
UDB033381
this study
Arrhenia leucotricha BBF-GC03091513 France MT967326
UDB033393
this study
Arrhenia leucotricha O-179285 Norway MT967330
UDB032090
this study
a Herbarium of primary (larger) collection on top and smaller copy below, in parentheses. For collections split between DAOM
and TU, DNA extracted from the TU copy.
b Direct submission; associated study unpublished, presumed in progress.
c Direct submission; no associated publication found.
d Specimens sent for sequencing, but package lost in the return mail, so no voucher tissue remains. Used here because data, usu-
ally also photo, and DNA available.
e Two separate sequences from the same basidioma.
f Direct submission, made independently for this publication.
g Same collection sequenced in different laboratrories at different times, resulting in two different sequences.
h In private herbarium of Sve-Åke Hanson. To be deposited to LD after access re-established following pandemic
142 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
Fig. 1a. The acerosa complex within Acerosa. Best-scoring maximum likelihood tree of the genus Arrhenia based on the fungal
ITS barcoding marker. Branch thickness is proportional to bootstrap support and support values for major and species-level
clades are given below branches. GenBank accession numbers and geographic origin (as ISO 3166-1 alpha-2 codes) are also
given. The branch length scale indicates changes per site.
latispora* (Fig. 2D, F) from the European Alps
agreed morphologically with the holotype, but be-
cause it was unavailable for sequencing, a collection
from the toporegion (LIP-0401569) is designated as
epitype. Although several other species in the com-
plex also produce spores of similar width (e.g. A. sub-
globisemen, A. svalbardensis, A. tillii), in addition to
its ITS sequence data, the species is set apart by its
alpine habitat, larger size, Pelargonium odour and
striking dark bluish-violet colour. Because the holo-
type for the pink-spored Rhodocybe tillii (WU-
18120) fell into the acerosa complex it is transferred
to Arrhenia as the sole representative of A. tillii*
(Krisai & Noordel.) Krisai & I. Saar (Fig. 2J). Arrhe-
nia subglobisemen* (Fig. 2G, H, I), has the widest dis-
tribution of any species of the complex, with collec-
tions from Estonia, France, Norway, Newfoundland,
and Labrador in arctic-alpine to woodland settings.
These agreed morphologically with the type speci-
men, but because it was not available for sequencing,
the species is epityped below with a collection from
the toporegion (BBF-GC15100901).
Sydowia 73 (2021) 143
Voitk et al.: The Arrhenia acerosa complex
Fig. 1b. The acerosa complex. Best-scoring maximum likelihood tree of the Arrhenia acerosa complex based on the fungal ITS
barcoding marker. Branch thickness is proportional to bootstrap support and support values for major and species-level clades
are given below branches. GenBank accession numbers and geographic origin (as ISO 3166-1 alpha-2 codes) are also given. The
branch length scale indicates changes per site. Species-level clades and unresolved grades are highlighted in coloured boxes and
types are indicated in red. For each terminal, nine characters are mapped, including phenotype, ecology, and distribution.
144 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
New species (in order of appearance in our tree;
more complete treatment under Taxonomy). Four
clades are described as new species, based on stable
composition and consistently high support, plus any
combination of similar morphology, region, habitat
and substrate. Arrhenia fenicola Hay & Thorn
(Fig. 3A, B) is represented by two collections (one
sequenced) found in the course of surveying the
macrofungi in the tall grass prairie of Ontario, Can-
ada, and two environmental sequences from the
prairies in Alberta, Canada. It forms small grey
pleurotoid basiomata with a rudimentary lateral
pseudostipe, growing on the ground or on fallen
grass litter. Arrhenia juncorum P.-A. Moreau & Cor-
riol (Fig. 3C) consists of two collections of light grey
astipitate pleurotoid bisporigerous basidiomata
from France, growing on dead leaves of live species
of Juncus in wet subalpine meadows. Arrhenia sval-
bardensis Gulden, I. Saar & Lücking (Fig. 3F, G)
consists of four collections of grey-brown pleuro-
toid collections from Svalbard, and DNA from a soil
sample from Prince Patrick Island, Northwest Ter-
ritories, Canada. Both 2- and 4-spored populations
are documented (Fig. 6H, I). Arrhenia leucotricha
P.-A. Moreau & Corriol (Fig. 3D, E) is a large clade
with collections from montane to subalpine Aus-
tria, France and Norway, of brown to grey pleuro-
toid tetrasporigerous basidiomata growing on dead
litter of larger wetland herbaceous plants.
Potential additional species (in order of appear-
ance in our tree). We suspect the following are good
species, but do not know them well enough to at-
tempt a description here. AC-1, with two Norwe-
gian collections, forms a well-supported sister clade
to A. subglobisemen. Although the separating
branch is short, these two collections differ consist-
ently from A. subglobisemen s.str. in two substitu-
tions and eight indels, resulting in a BLAST iden-
tity of slightly below the 98.5% level used for spe-
cies hypotheses in UNITE. We list the clade as a
potential species, awaiting further investigation.
AC-2 (Fig. 4A) is a singleton from Estonia, found to
deviate from its pathway by 25 ITS apomorphies.
Unfamiliar with this potential species, we are not
able to describe it on the basis of a single collection.
AC-3 (Fig. 4B) is a pink terricolous species, seem-
ingly close to the pink A. tillii. However, it does not
cluster with A. tillii s.str., but forms a paraphyletic
grade with it. The species is consistently collected
on old rotten coniferous wood, which seems to be a
required substrate. Despite the pink colour, the 20
substitution and 19 indel phylogenetic difference,
based on ITS data, of AC-3 from A. tillii, as well as
the apparently different substrate, make us treat
this clade as a potentially separate species, pending
further investigation. AC-4 is a singleton from
Swedish horse pastureland that has remained in a
supported sister relationship with the new species
A. juncicola through all our trees and analyses. We
lack sufcient familiarity with it, and treat it as a
potential species requiring further investigation.
AC-5 (Fig. 4G) is a singleton sequence from a pink
basidioma from Québec, Canada. Although it has
remained phylogenetically remote from the Euro-
pean pink species, this sequence has not occupied a
consistent position in our trees. Yves Lamoureux,
who collected the specimen, reports that it was im-
mature, with no spores to be found. We list this very
distinct pink North American collection as a poten-
tial species, whose nature we are unable to rene
further at this point. Its relationship to the two Ca-
nadian environmental samples forming grade G-4,
from the Northwest Territories and British Colum-
bia, requires further elucidation. AC-6 (Fig. 4H) is a
singleton from the Swedish high arctic. Further col-
lections and familiarity are required to dene this
potential species. AC-7 is made up of two arctic-
alpine collections forming a moderately supported
sister clade to A. leucotricha. The voucher collection
for U66436 was collected in the Vanoise National
Park in the French Alps as Phaeotellus griseopalli-
dus, and O-50445 is a pleurotoid species from Sval-
bard, the second species in the acerosa complex
known in the archipelago. Some of our trees have
shown this clade apart from A. leucotricha, al-
though most place them in a sister relationship,
with each arm supported up to 100 %. We present it
as a potential species, until additional sequence
data claries its position, and additional collections
permit greater familiarity with it.
Groups of unresolved species (in order of ap-
pearance in our tree) consist of one group (G-1) of
pleurotoid specimens, two groups (G-2, G-3) of om-
phalinoid specimens, and one group (G-4) com-
posed of two environmental samples from Canada.
The topology of some of these sequences varied
widely in different iterations of our trees. We sus-
pect that each group contains more than one spe-
cies, but ITS data has been insufcient to delimit
species in these groups, even with the aid of mor-
phologic and other characters, where available. G-1
contains European collections from Scandinavia to
Spain, including highland collections growing on
wood (Fig. 4C, D), one on Ammophila arenaria in
sand dunes of The Netherlands (Fig. 4E) and a
Swedish collection (Fig. 4F) growing on horse dung
(Hanson 2017). Some of these collections formed an
Sydowia 73 (2021) 145
Voitk et al.: The Arrhenia acerosa complex
unsupported cluster on a few Bayesian analyses. Al-
though these specimens are bisporigerous and fruit
on cellulose-containing substrate, we suspect that
there is more than one species involved. ITS data
seems to be inadequate to resolve the species and
pending additional studies, we opt to leave this
group without designating potential species bound-
aries. G-2 consists of nine sequences from two envi-
ronmental samples (from USA and China) and sev-
en terricolous omphalinoid basidiomata, collected
in Argentina (Fig. 5E), Austria (Fig. 5D), Estonia,
and northeastern North America (Fig. 5A, B, C). The
rst three sequences come from two collections
from northeastern North America, the rst from
coastal hardwoods and the second from harsh al-
pine conditions at the summit of Mt Washington,
NH. The second specimen was sequenced twice, ac-
counting for three sequences for two specimens. Al-
though we are condent that the rst two collec-
tions are conspecic, we lack sufcient phylogenet-
ic data to comment on the whole group, and leave
the study of the omphalinoid species within the ace-
rosa complex for a separate investigation. G-3,
somewhat removed from G-2, contains sequences
from four European environmental samples and
three basidiomata, two of which are documented as
omphalinoid, one illustrated (Fig. 5F). No informa-
tion is available for the remaining basidioma, col-
lected by Kühner, because there is only 1–2 mm of
the base of the stipe left in G! The rst sequence in
the group, from a 4-spored basidioma, has moved to
several locations with different iterations of our
tree, but the other two non-environmental sequenc-
es, both forming 2-spored basidiomata, clustered
together throughout with >70 % support, until they
parted with the addition of the environmental sam-
ples. We are unable to assess G-3 further with avail-
able data and leave its elucidation, together with
G-2, to future studies of the omphalinoid species
within the acerosa complex. As mentioned, G-4
consists of two seemingly heterospecic environ-
mental samples from western Canada. The relation-
ship of one of them to AC-5 remains to be deter-
mined. Lack of morphologic data prevents further
comment, and we leave them to be sorted out in the
future.
Other ndings. We were unable to study A. acer-
osa var. tenella (= A. kuehneri), because Kühner’s
lectotype, curated in G, is not available for loan or
destructive sampling needed for molecular genetic
studies. It was collected in Algeria, and we found no
suitable collection from the toporegion for epitypi-
cation. Because of the diversity of parochial spe-
cies in this complex, we did not consider it appro-
priate to epitypify it with a remote collection. Fi-
nally, the specimen we identied as Arrhenia sub-
globispora – not to be confused with A. subglobise-
men – fell in a different location within Arrhenia,
well outside the acerosa complex (not shown); it did
not fall with the specimen identied as A. subglo-
bispora in Fig. 1a, which we presume to be a misi-
dentication, because that species with clamp con-
nections is unexpected among its clampless neigh-
bours. Our single specimen identied as Gerronema
josserandii (UNITE: UDB035029) fell outside Ar-
rhenia altogether (not shown).
Taxonomy
Arrhenia acerosa
(Fr.) Kühner, Bull. Soc. linn. Lyon,
49: 893, 992. 1980. – Figs. 2A, 6A
MycoBank no.: MBT 393700
Typification. – Holotypus not designated.
Neotypus, here designated: SWEDEN. Småland,
Femsjö, Hägnen, close to Bokhultet, “along earthy
path amongst twigs, chips, etc.”, 22 August 1943,
leg. Seth Lundell (Lundell & Nannfeldt, Fungi exs.
Suec. no. 1761), F-151993! (UPS). GenBank/UNITE
ITS = MT967312 / UDB032044. UNITE
SH1526144.08FU.
Agaricus acerosus Fr. (basionym) Systema my-
cologicum 1: 191. 1821
Pleurotus acerosus (Fr.) Quél., Mém. Soc.
Émul. Montbéliard, Sér. 2 5: 246. 1872
Dendrosarcus acerosus (Fr.) Kuntze, Revis.
gen. pl. (Leipzig) 3(3): 463. 1898
Pleurotellus acerosus (Fr.) Konrad & Maubl.,
Icon. Select. Fung. 6: 361. 1937
Phaeotellus acerosus (Fr.) Kühner & Lamoure,
Botaniste 55(1–6): 25. 1972 (comb. inval.)
Leptoglossum acerosum (Fr.) Parker-Rhodes,
Trans. Brit. Mycol. Soc. 37(4): 338. 1954
Omphalina acerosa (Fr.) M. Lange, Nordic J
Bot.1: 695. 1981
Panellus acerosus (Fr.) Z.S. Bi, in Bi, Zheng &
Li, Acta Mycol. Sin., Suppl. 1: 285. 1987 (1986)
Description of neotype
Macromorphology. – One larger, one
smaller basidioma, and fragments of two smaller
basidiomata; some wood fragments attached to one
basidioma, no bryophyte remnants. Basidiomata
spathulate, fan-shaped to reniform, astipitate. Pi-
leus (as dry) up to 15 mm long from point of attach-
ment to margin and equally wide, thin-eshed,
young margin incurved, becoming straight, lobed,
upper side smooth, medium grey brown (N67, 69, 70,
P68, 70), white pubescent at point of attachment.
Lamellae normally shaped and spaced, not forked,
146 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
some lamellulae developed from margin, slightly
darker than the pileus (R 69-70).
M i c r o m o r p h o l o g y . – Basidiospores (1 ba-
sidioma, 1 collection, 1 observer, n =50) (5.8)6.8–
8.7(9.7) × 3.4–3.9(4.4) µm, average 7.4 × 3.8 µm,
Q = 1.4–2.5, Qavg = 2.0; narrowly elliptical to slightly
lacrymoid, blunt, with prominent apiculus, hyaline,
smooth. Basidia 21–25 × 6–7 µm, 4-spored. Cystidia
absent. Hymenophoral trama made of approx.
3–10 µm wide, hyaline hyphae, some with brown in-
crusted pigment. Pileipellis a cutis of radially re-
pent, 3–10 µm wide, ± cylindrical, thin-walled, yel-
low brown hyphae with sparse incrustation. Tomen-
tum at the point of attachment to the substrate is
made up of of smooth, hyaline, cylindrical, long
celled hyphae forming bundles. Clamp connections
at base of basidia and throughout all tissues. Pig-
ment membranal and incrusting.
H a b i t a t . – Along earthy path, among twigs,
chips etc., attached to woody debris.
C o m m e n t s . – There are two collections of
Pleurotus acerosus (Fr.) in the Lundell & Nannfeldt
exsiccatum. We have chosen no. 1761 as neotype. It
contains material collected at Femsjö, the collecting
area of Elias Fries (Petersen & Knudsen 2015) and
thus the type locality for Ag. acerosus s. str., grows
in similar habitat and on similar substrate as de-
scribed in the protologue, and agrees well with the
current description and our photo (Fig. 2A) of the
species. It differs widely from Fries’ (1874a) illustra-
tion of A. acerosa, which shows yellow-brown, fan-
shaped specimens with fairly long, thin, lateral, ta-
pering and strigose pseudostipes attached to moss,
which Fries notes shows a dark variety (varietam
fuscam) of Ag. acerosus, thus already noting the di-
versity in the complex. This neotype collection, no.
1761 of the Lundell & Nannfeldt exsiccatum, fol-
lowed their no. 1128 collection from Upland further
north in Sweden, which Lundell considered the
typical form of the species, and was distributed in
order to show the variability of the species. Labels
of both collections have references to illustrations
by Lange (1936) and pl. 63B is indicated as repre-
sentative of the material distributed in no. 1761,
showing grey, pleurotoid, short stipitate specimens.
In the phylogenetic tree (Fig. 1b) the neotype falls in
a clade with a specimen from Estonia and one from
Norway, Vestfold county in SE Norway. The latter
specimen (Fig. 2A) comes from similar habitat
(pathside bare earth with moss) and has similar
spores (6.8–8.7 × 3.5–4.4 µm, Qavg = 2.1, narrowly el-
liptical to slightly lacrymoid).
Additional specimens examined. –
ESTONIA. Valga County, Ähijärve, 57.685725° N,
26.511601° E, on a sandy forest path, 13 September
2015, leg. Apo Ahola & Kersti Gillen, AA-2015-59,
TU-109632. NORWAY. Vestfold, Nøtterøy, Teiesko-
gen, 59.2018° N, 10.4861° E, on bare soil by a forest
path, 21 September 1987, leg. Arne Aronsen, A60/87,
O-189467.
Arrhenia fenicola
C.R.J. Hay & Thorn, sp. nov.
Figs. 3A–B, 6B
MycoBank no.: MB 836882
Ty p i f i c a t i o n . – Holotypus: CANADA. On-
tario, Essex County, Windsor, in Herb Gray Park-
way, FRS#23, on bare soil in remnant tallgrass prai-
rie, 23 October 2015, leg. Chris Hay, HA10! (UWO-
F44). GenBank ITS = KY706173.
E t y m o l o g y. – Fenicola, from Latin fenum
(hay), indicates the habitat in tallgrass or hayeld
of this species.
D i a g n o s is . – A small, grey pleurotoid agaric
growing on soil or grass litter in Canadian prairies,
with tan to grey lamellae and an eccentric, white-
tomentose pseudostipe, elliptical spores and
4-spored basidia. Differs from other species of the
acerosa complex by its North American distribu-
tion, prairie habitat, and diagnostic ITS sequence.
M a c r o m o r p h o l o g y . – Pileus dimidiate,
5–12 mm broad, mouse grey (5E2) to greyish brown
(6E2) or smoke grey (5EF1), dry, tomentose, nonhy-
grophanous, with sharp, incurved, white-rimmed
margin. Lamellae sharp, distant, radiating from the
eccentric stipe, with two series of lamellulae, at rst
greyish off-white (5AB1) then yellowish grey (to
4½C3), drying brownish grey (5EF1½), the margins
concolorous, with pallid (white to 4½AB1½) con-
text showing between lamellae towards the stipe.
Stipe an eccentric pseudostipe, short and stubby, or
absent, up to 3 mm in diam and 3 mm long, con-
colorous with the upper pileus, covered with cot-
tony white tomentum as it descends. Context thin,
soft, cottony, white. Taste and smell not noted.
Sporeprint white.
M i c r o m o r p h o l o g y . – Basidiospores (1 ba-
sioma, 1 collection, 1 observer, n = 30) 7.3–8.4(9.2) ×
4.0–5.0(5.6) µm, average 7.9 × 4.5 µm; Q = 1.6–1.9(2.0),
Qavg = 1.8; hyaline, inamyloid, thin-walled, smooth,
elliptical, varying from nearly cylindrical to broad-
ly elliptical, a few slightly constricted. Basidia 21–
29 × 5.9–6.9 µm, 4-spored, clavate to suburniform.
Cystidia absent. Hymenophoral trama made of in-
ated, thin-walled hyphae, commonly 9–19 µm
diam. Pileipellis a loose cutis, with mostly repent,
tubular hyphae, 3.4–6.8 µm diam., with both cyto-
plasmic and incrusting pigments. Pileitrama of hy-
Sydowia 73 (2021) 147
Voitk et al.: The Arrhenia acerosa complex
Fig. 2. Previously described species of the acerosa complex treated here, in alphabetical order. A. Arrhenia acerosa s. str.,
O-189467, Norway, photo: Arne Aronsen. B–D. Arrhenia glauca. B. Epitype, WU-6564, Austria, photo: Anton Hausknecht. C. Lec-
totype, Germany, illustration: August Batsch. D. GB-0058855, Sweden, photo: Leif Strindvall. E–F. Arrhenia latispora. E. WU-
22359, Austria, photo: Anton Hausknecht. F. Epitype, LIP-0401569, France, photo: Pierre-Arthur Moreau. G–I. Arrhenia subglo-
bisemen. G. DAOM-981251, Canada, NL, photo: Andrus Voitk. H–I. Epitype, BBF-GC15100901, France, photo: Gilles Corriol.
J. Arrhenia tillii, holotype, WU-18120, Austria, photo: Anton Hausknecht.
148 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
aline, tubular to slightly inated hyphae 3.5–8 µm
diam. Clamp connections present at base of basidia
and throughout all tissues
H a b it at . – On bare soil or grass litter or dead
stalks in tallgrass prairies, in late autumn.
D i s t r i b ut i o n . – Known from prairie in Al-
berta and Ontario, Canada.
C o m m e n t s . – Both Ontario collections match
each other well, with average spore measurements
of 8.1 × 4.6 um, Qavg = 1.76, but the second failed to
yield ampliable DNA on two attempts. Two envi-
ronmental samples from Alberta prairie suggest
this small species may have a wider North Ameri-
can prairie distribution.
Additional specimen examined.
CANADA. Ontario, Lambton County, Walpole Is-
land First Nation, on bare soil in remnant tallgrass
prairie with Populus deltoides, 30 October 2015,
leg. Chris Hay, PO21 (UWO-F70).
Arrhenia glauca
(Batsch) Bon & Courtec. Doc. My-
col. 18: 70. 1988. Figs. 2B–D, 6C
MycoBank no.: MBT 393701, MBT 393702
Ty p i fi c a t i o n . – Holotypus not specically
mentioned in the protologue. Lectotypus, here des-
ignated, Batsch: Elenchus fungorum, Continuo pri-
ma: illustration tab. 24, no 123 a–c. 1786. Epitypus,
here designated: AUSTRIA. Niederösterreich, Horn,
Maissau, Raan, Raanholz, along path on bare soil, 8
Nov 1987, leg. Anton Hausknecht, WU-6564! (WU),
GenBank/UNITE MT967319 / UDB039746. UNITE
SH1526142.08FU.
Agaricus glaucus Batsch (basionym) Elenchus
fungorum, Continuo prima: 169, t24:123. 1786
Agaricus epigaeus var. glaucus (Batsch) Pers.,
Synopsis methodica fungorum: 484. 1801
Cantharellus glaucus (Batsch) Fr., Hymenom-
yc. eur. (Upsaliae): 460. 1874
Merulius glaucus (Batsch) Kuntze, Revis. gen.
pl. 2: 862. 1891
Leptotus glaucus (Batsch) Maire, Meded.
Proefstn W. Java, Kagok-Tegal 15(2): 5. 1933
Geotus glaucus (Fr.) Pilát & Svrcek., Ceská
Mycol. 7(1): 10. 1953
M a c r o m o r p h o l o g y. – Basidiomata spathu-
liform, astipitate to short laterally stipitate. Pileus
5–10 mm wide, spathuliform, semicircular to almost
circular, convex only when very young, soon at-
tened to even slightly depressed with umbo at inser-
tion point, distinctly whitish tomentose-brillose,
not striate, tomentum silvery whitish, ground col-
our under tomentum blue-grey, dark grey (23D1),
some parts more watery dull brownish grey (6C1-2)
with age, towards margin whitish, sometimes with a
darker submarginal zone; not hygrophanous, slight-
ly fading when drying; surface densely brillose-
tomentose all over, margin straight, almost not en-
rolled, white, tomentose. Lamellae a bit distant,
narrowly adnate to shortly decurrent, straight, nar-
row, rarely forked especially when aged, 1–7 lamel-
lulae, light grey to grey (8B-C1, 8C2) with dull
brownish shades (8C2); lamellar edge smooth, ob-
tuse, paler than lamellar side. Stipe 1 mm wide, ab-
sent to 3 mm long, lateral, densely covered by white
tomentum; white hairs at base attached to substra-
tum. Exsiccatum pileus grey-brown (5D3-4), lamel-
lae bronze to dark brown (5E5, 6F6), except still
whitish stipe base. Smell and taste not recorded.
M i c r o m o r p h o l o g y . – Basidiospores (1 ba-
sidioma, 1 collection, 1 observer, n=60) (5.3)5.8–
7.3(8.1) × (2.7)3.4–4.5(5.5) µm, average 6.6 × 4.0 µm;
Q = (1.2)1.4–1.9(2.4), Qavg = 1.7; lacrymoid to pip-
shaped, ovoid, or broadly elliptical, smooth, hyaline,
often in tetrads, inamyloid, acyanophilous. Basidia
(17.5)19–25.5(28.7) × (5.8)6–8(9.5) µm, 4-spored,
rarely 2-spored, cylindrical to slightly clavate, hya-
line. Lamellar trama subregular, similar to pileit-
rama. Cystidia absent. Pileipellis near insertion
point a cutis, a plagiotrichoderm for the rest of the
pileus, made up of smooth hyphae, 4–9 µm wide;
terminal ends cylindrical or slightly clavate. Pileit-
rama made up of mostly parallel hyphae, becoming
more irregular near the hymenium, made of cylin-
drical to swollen hyphae 4–7 µm diam, partially dis-
tinctly incrusted. Clamp connections at base of ba-
sidia and throughout all tissues.
H a bi t a t. – The basidiomata of the epitype col-
lection grew directly on bare organo-mineral soil
along a forest path.
D i s t r i b u t i o n . In addition to the mon-
tane zone of the Bohemian Forest in the granite and
gneiss plateau Waldviertel, conrmed from Austria,
France, Germany, Norway, and Sweden in our tree
(Fig. 1b), additional specimens or soil samples from
these countries and Estonia in UNITE
SH1526142.08FU.
C o m m e n t s . – The description is based on
WU-6564. Arrhenia glauca is characterized by its
distinctly pale, blue-grey, very small, spathulate ba-
sidiomata covered with a white tomentum, by the
greyish lamellae and the thin white tomentose stipe.
The habitus of the epitype collection agrees strik-
ingly with Batsch’s illustration, i.e. with the lecto-
type, also from central Europe, supporting the epi-
typication.
Additional specimens examined.
AUSTRIA. Lower Austria, Wilhelmsburg, Göblas-
Sydowia 73 (2021) 149
Voitk et al.: The Arrhenia acerosa complex
Fig. 3. New species of the acerosa complex described here, in alphabetical order. A–B. Arrhenia fenicola holotype, UWO-F44,
Canada, ON, photo: Chris Hay. C. Arrhenia juncorum, holotype, LIP-0401674, France, photo Pierre-Arthur Moreau. D–E. Arrhe-
nia leucotricha. D. WU-6774, Austria, photo: Anton Hausknecht. E. BBF-CH13091220, France, holotype, photo: Gilles Corriol.
F–G. Arrhenia svalbardensis. F. O-76070, Norway, Svalbard, photo: Arne Aronsen. G. O-50444, Norway, Svalbard, photo: Kol-
bjørn M. Jenssen.
150 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
bruck, 48° 4’ 52’’ N; 15° 35’ 36’ E, on bare soil in
pasture, 13 October 1991, leg. Wolfgang Klofac,
WU-9855. FRANCE. Pas-de-Calais, Guînes, forêt
domaniale de Guînes, on clay soil under Quercus
robur and Carpinus betulus, leg. Pierre-Arthur
Moreau, 50.8455°N 1.8614°E, PAM06091108, LIP-
0401688. Rothreid, Vosges, 48.046078°N, 7.033331°E,
on soil and wood debris in beech-r mountain for-
est, 28 September 1997, leg. Gilles Corriol,
GC97092813. GERMANY. Lückendorf, 50.83 N
14.76 E, October 2014, KP-965766. NORWAY. Vest-
fold, Hof, Rønnenberg, 59.5541 °N, 10.0375 °E, wet
meadow, on Carex, 1989, leg. Per Marstad, PM114-
89, O-64979. Vestfold, Nøtterøy, Teieskogen,
59.2018 °N, 10.4861 °E, on moss and soil, 2 October
1988, leg. Arne Aronsen, A68/88, O-189477. SWE-
DEN. Västergötland, Vänersborg, Västra Tu4nhem,
Hunneberg, Landgedalen, 7 October 2000, on bare
soil, leg. Leif & Anita Strindvall, LAS00/215, GB-
0058858. Skåne, Ignaborga, 56.1217 °N, 13.82703 °E,
on rotten deciduous wood in deciduous forest, 15
September 2003, Björn Nordén, GB-0017687.
Västergötland, Trollhättan, Jonstorp Ö, on soil in
natural meadow, leg. Leif & Anita Strindvall,
LAS06/149, GB-0058855.
Arrhenia juncorum
P.-A. Moreau & Corriol, sp. nov.
– Figs. 3C, 6E
MycoBank no.: MB 836883
Ty p i f i c a t i o n . – Holotypus: FRANCE.
Haute-Loire, Saint-André-en-Vivarais, on Carex
rostrata mixed with Juncus spp. in open wetland, 25
September 1998, leg. Pierre-Arthur Moreau,
PAM98092503 (LIP-0401674). GenBank/UNITE
ITS = MT967322 / UDB033394. UNITE
SH1526152.08FU
E ty m ol o g y. – Juncorum, from the Latin “jun-
cus” (rush), base for the name of the genus Juncus,
sole or partial host of both collections.
D i a g n o s i s . – A small, astipitate, conchoid
species insititious on dead leaves of living Juncus
and Carex species, distinguished by long, somewhat
pyriform spores in front view and hyphae that are
smooth in the pileipellis but distinctly incrusted in
the lamellar trama. Differs from most species in the
acerosa complex by its lack of stipe, from most wet-
land species by its substrate, from other herbicolous
species by its habitat, and from all by its ITS se-
quence data.
M a c r o m o r p h o l o g y . – Basidiomata astipi-
tate, conchoid, circular, 0.8–1.8 cm diam., astipitate,
attached by a lateral point. Pileus not hygropha-
nous; surface densely silky, silvery white with light
grey tones towards margin when mature; attach-
ment point thick, white tomentose; margin soon un-
rolled, smooth, white. Lamellae rather distant (12
reaching the attachment point, 3–5 unequal lamel-
lulae per lamella), not forked, light grey becoming
whitish when drying; edge truncate, smooth, grey-
ish. On exsiccatum, pileus and lamellae uniformly
ochre-brown. Smell none noted.
M i c r o m o r p h o l o g y . – Basidiospores (2 ba-
siomata, 2 collections, 2 observers, n = 58) (6.5)7.0–
9.6(10.1) × (3.2)3.7–5.0(5.9) µm, average 8.3–3.6 µm;
Q = 1.6–2.4, Qavg = 2.3; narrowly ellipsoid to slightly
lacrymoid, some more ellipsoidal to somewhat pyri-
form in front view, mostly with adnexed base. Ba-
sidia 28–38 × 7.5–8(11) µm, shortly cylindrical, col-
ourless, 4-spored. Cystidia absent. Subhymenium
ramose. Hymenophoral trama hyphae 5–12 µm wide,
mostly incrusted by a distinct pigment bright yellow
in KOH, the longest hyphae slender and smooth.
Pileipellis a prostrate trichocutis made of colorless,
long hyphae 35–90 × 5–7.5 µm, inate to lobate at
apex, with yellowish intraparietal pigment, not in-
crusted. Pileitrama thin, made of a few layers of
slender hyphae 3.5–5(12) µm wide, irregularly in-
crusted. Clamp connections present at all septa.
H a b i t a t . – On dead leaves of Carex and Jun-
cus spp. in open montane wetlands; autumn.
D i s t r i b u t i o n . – So far only known from
France.
C o m m e n t s . – We suspect that more collec-
tions of this uncommon species will reveal a wider
European distribution. Arrhenia fenicola is a grass-
land denizen, but neither a montane nor a wetland
species, is limited to North America, is terricolous
on dead herbaceous litter, has a short pseudostipe,
and differs microscopically by a mixed, cytoplasmic
and incrusting pigmentation on pileipellis. The
more common A. leucotricha also grows in montane
wetlands, but is bigger, grows on dead herbaceous
litter, not dead leaves of living plants, and has a
short pseudostipe. Two undescribed herbicolous
specimens occur in G-1: WU-1294 grows on living
Ammophila in sand dunes, not wetland; O-65097 is
reported to be morphologically very similar and
growing on living Juncus in barren coastal wetland
(Aronsen 1992). However, the tree topology (Fig. 1b)
does not support conspecicity, and sequence diver-
sion from A. juncorum reveals 18 differences (most-
ly substitutions), leaving a 97.2 % similarity. This is
one of the many homoplasies in the complex, dem-
onstrating that similar phenotype does not neces-
sarily mean genetic proximity.
Additional specimen examined.
FRANCE. Hautes-Pyrénées, Gaillagos, on Juncus
Sydowia 73 (2021) 151
Voitk et al.: The Arrhenia acerosa complex
Fig. 4. Undescribed pleurotoid species of the acerosa complex, in phylogenetic order, as they appear in our tree (Fig. 1b). A. AC-2,
TU-120494, Estonia, photo: Vello Liiv. B1–2. AC-3, BBF-GC13082701, France, photo: Marcel Vega. C–F. G-1. C. WU-8395, Austria,
photo: Anton Hausknecht. D. BBF-GC13082806, France, photo: Gilles Corriol. E. WU-12194, Austria, photo: Anton Hausknecht.
F. LD, Sweden, photo: Sven-Åke Hanson. G. AC-5, CMMF-003682, photo: Yves Lamoureux. H. AC-8, GB-0202287, Sweden, Lap-
land, photo: Pierre-Arthur Moreau.
152 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
acutiorus, in semi-shaded wetland, 12 September
2013, leg. Carole Hannoire & Gilles Corriol,
CH13091225, BBF-CH13091225.
Arrhenia latispora
(J. Favre) Bon & Courtec. Doc.
Mycol. 18(69): 37. 1987. – Figs. 2E–F, 6E
MBT 393703
Ty p i f i c a t i o n . – Holotypus: SWITZER-
LAND. Grissons: Sesvenna Valley, near the Sesven-
na upstream toward Marangun, on dead moss, 2400
m a.s.l., 24 August 1943, leg. Jules Favre (G13896!).
Epitypus, here designated: FRANCE. Savoie, Bourg-
Saint-Maurice, Arc 2000 towards col des Frettes,
2250 m a.s.l., 24 August 1999, leg. Pierre-Arthur
Moreau PAM99082402 (LIP-0401569!). GenBank/
UNITE ITS = MT967324 / UDB033395. UNITE
SH1526154.08FU.
Pleurotellus acerosus f. latisporus J. Favre,
Ergebn. wiss. Unters. schweiz. Natl Parks 5: 38, 199.
1955.
Phaeotellus acerosus va r. latisporus (J. Favre)
Jamoni & Bon, Riv. Micol. 36(1): 6. 1993.
M a cr om or p h o l o g y. – Basidiomata usually
20–30 mm wide, eccentrically stipitate. Pileus
5–30 mm wide, spathuliform to petaloid, convex
then attened, indistinctly striate, bluish-violet
dark grey when young, somewhat more brownish
with age, lighter towards margin, sometimes with a
darker submarginal zone; not hygrophanous, slight-
ly fading when drying; surface densely brillose-
tomentose all over, becoming glabrous at centre
with age; margin wavy, inrolled, white, pruinose.
Lamellae crowded, with 2–3 series of lamellulae,
adnate to decurrent, not forked, light grey with
pinkish shades when aged; lamellar edge smooth,
truncate, white at rst then concolorous with pile-
us. Stipe 3–6 × 3 mm, short, lateral to strongly ec-
centric, densely covered by white tomentum; no rhi-
zomorphs seen. Exsiccatum entirely black except
stipe tomentum. Smell distinct of Pelargonium.
Taste not recorded.
M i c r o m o r p h o l o g y . – Basidiospores (1 ba-
sidioma, 1 collection, 1 observer) 7.8–9.5 × 6.3–
6.8 µm, spherical in youth becoming pyriform, then
lacrymoid at maturity, smooth, hyaline. Basidia 22–
28 × 7–8 µm, 4-spored, cylindrical, hyaline. Basidi-
oles and immature basidia often enveloped by
colorless mucus. Hymenophoral trama branched,
orderly, similar to pileitrama. Cystidia absent.
Pileipellis a trichoderm, dense at the margin, thin-
ning out toward the base, made of smooth hyphae,
4–7 µm wide, bulging above septa; terminal ends
long, cylindrical or broadly drawn out. Pileitrama
parallel, becoming more intertwined near the hy-
menium, made of cylindric to swollen hyphae of
5–11 µm diam, nely but distinctly encrusted; oc-
casional yellow, unbranched, cylindrical, glutinous
hyphae seen, 3–4 µm diam. Clamp connections at
base of basidia and throughout all tissues.
H a b i t a t . – Bare organo-mineral soil with
young mosses.
D is tr i b u t i o n. – So far, only conrmed from
the lower alpine zone of the Alps.
Additional collections studied.
AUSTRIA. Tirol, Lienz, Nußdorf-Debant, Neualpl-
seen, 46° 43’ 52” N; 12° 24’ 35” E, on soil among moss,
26 August 2002, leg. Anton Hausknecht, WU-22359.
FRANCE. Savoie, Bourg-Saint-Maurice, Arc 2000
toward Col des Frettes, 45.561186° N, 6.816898° E,
on bryophytes on mineral slope along a road, lower
alpine zone, 2250 m a.s.l., basic soil, 23 August 2001,
leg. Gilles Corriol, GC01082301, BBF-GC01082301.
C o m m e n t s . – Description based primarily on
PAM99082402. It is a seldom-encountered and
seemingly regional species, but the name has been
misapplied to other wide-spored species in the
complex. This is the largest species in the complex,
the pileus occasionally exceeding 30 mm in width,
thicker and more opaque esh, dark violet colour
(turning black on drying), Pelargonium odour and
ITS sequences should serve to distinguish it from
other species in the complex.
Arrhenia leucotricha
P.-A. Moreau & Corriol, sp.
nov. – Figs. 3D–E, 6F
MycoBank no.: MB 836884
Ty p i f i c a ti o n . – Holotypus: FRANCE. Haute-
Loire, Saint-André-en-Vivarais, on bare peat in an
acidic peat bog under Pinus sylvestris, 25 Septem-
ber 1998, leg. Pierre-Arthur Moreau & Pierre Roux,
PAM98090107 (LIP-0401673). GenBank/UNITE
ITS = MT967329 / UDB033396. UNITE
SH1526146.08FU.
Etymology. Leucotrichus: from Greek,
λευχο: white, τριχός: hairs, refers to the white hairy
tomentum covering the stipe and a part of surface
of the pileus.
D i a g no s is . – A common European pleurotoid
species of montane to alpine wetlands, with a short
but distinct lateral white-tomentose pseudostipe
found on more or less peaty soil and dead litter of
hygrophilous herbaceous species. Differs from most
species in the acerosa complex by its wetland hab-
itat, from most wetland species by its terricolous
litter substrate, and from all by its ITS sequence
data.
Sydowia 73 (2021) 153
Voitk et al.: The Arrhenia acerosa complex
Fig. 5. Undescribed omphalinoid species of the acerosa complex, in phylogenetic order, as they appear in our tree (Fig. 1b).
A–E. G-2. A. TENN-074409, USA, TN, photo: Jacob Kalichman. B. HUH-11394, USA, NH, photo: Andrus Voitk. C. QFB-32684,
Canada, QC, photo: Renée Lebeuf. D. WU-25862, Austria, photo: Irmgard Krisai-Greilhuber. E. FLAS-F-64782, Argentina, photo:
Matthew Smith. F. G-2, WU-32560, Austria, photo: Wolfgang Klofac.
154 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
M a cr o m o r p ho l o gy. – Basidiomata gregari-
ous, spathulate to abelliform, substipitate with a
lateral bulge or rudimentary pseudostipe, exuose
when old but never lobate. Pileus 10–25 mm long
from point of attachment to margin, striate, becom-
ing more conspicuous with age; surface brillose
with dense to white-silky brils, becoming sparse
with age, strongly hygrophanous, dark grey-brown
towards base and gradually fading to ochraceous-
pellucid to almost white all over, whitish and
opaque when dried; margin shortly incurved, white
pruinose. Lamellae crowded, narrow with straight
lamellar edge, 12–20 reaching the base, 3–4 series of
lamellulae, occasionally forked, light to dark grey,
remaining dark on exsiccata; lamellar edge smooth,
narrow, concolourous. Pseudostipe 1–3 mm long,
densely covered by a white hairy tomentum usually
also covering cap towards base. Flesh with rancid
odour on GC98092305, not pelargonium-like. Taste
not distinctive. Exsiccatum, uniformly bluish black,
with contrasting white tomentum.
M i c r o m o r p h o l o g y . – Basidiospores (3 ba-
sidiomata, 3 collections, 2 observers, n = 103)
(5.9)6.5–9.2(10.1) (3.2)3.6–5.5(5.9) µm, average 4.4 ×
7.5 µm; Q = 1.8–2.4, Qav = 1.7; narrowly cylindrical
to pyriform in front view, usually blunt and broader
at apex, often incurved on inner side; base adnexed.
Basidia 25–32 (43) × 6.7–8.5 µm, 4-spored, some
with long slender base, wall often thickened and
brownish at base on the type collection. Cystidia
absent. Subhymenium ramose, a mix of short and
long tapering elements, some thick-walled and
brownish. Pileipellis 50–60 µm thick, a more or less
erect trichocutis; terminal elements 30–55 × 5–7 µm,
cylindrical, clavate to subcapitate, smooth and pale;
other elements with a yellow-brown, with zebra
pattern incrustation. Pileitrama 60–80 µm thick,
made of interwoven hyphae 3.5–10 µm wide, pale
brown, mostly smooth, the slenderest coarsely in-
crusted. Basal tomentum made of long, smooth, hy-
aline hyphae 4.5–5 µm wide. Clamp connections
present at all septa.
H a b i t a t . – Mineralized peat, wet organic soil
and damp litter of hygrophilic plants (e.g. Juncus
effusus), from montane to alpine zones. August-
September.
D i s t r i b u t i o n . – Known from Europe (Aus-
tria, France, Norway).
Comments. – Arrhenia leucotricha, with its
distinct hairy lateral stipe, 4-spored basidia and el-
lipsoid to subpyriform spores, is one of the most
common acerosa-like species in European highland
wetlands. See Comments under A. juncorum for dif-
ferences from it and other wetland species. The col-
oured basidia (brownish intraparietal pigment to-
ward the base and in subhymenial hyphae) seem
characteristic, but this needs to be conrmed by
systematic investigation throughout the complex.
The relationship of this species with the putative
species AC-9 remains to be elucidated.
Additional specimen examined.
FRANCE. Hautes-Pyrénées, Gaillagos, wetland
with Juncus effusus in a cow hoof print, 12 Septem-
ber 2013, leg. Carole Hannoire & Gilles Corriol,
CH13091220 (in BBF). Haute-Garonne, Cuguron,
acid peat-bog, on dead Juncus stem, 15 September
2003, leg. Gilles Corriol, GC03091513 (in BBF).
Haute-Garonne, Cuguron, acid peat-bog, directly
on peaty soil, 15 September 2003, leg. Gilles Corriol,
GC03091514 (in BBF). Lozère, Linguas (Mont
Aigoual), on dead Juncus stem in acid peaty soil,
23 September 1998, leg. Gilles Corriol, GC98092305.
Arrhenia subglobisemen
Corriol, Bull. Mycol. Bot.
Dauphiné-Savoie 222: 14. 2016. – Figs. 2G–I, 6G
MBT 393704
Ty p i fi c at i o n. – FRANCE. Haute-Savoie, La
Chapelle-Rambaud, near la Roche-sur-Foron, 23
October 1938, leg. Carlo Poluzzi (Holotypus G, her-
bier Jules Favre, as Pleurotellus tremulus, num.
G-9922!) designated in Corriol (2016). Epitypus
here designated: FRANCE. Vallon de la Prade, pla-
teau de Payolle, Ancizan, Hautes-Pyrénées, October
9, 2015, leg. Gilles Corriol (GC15100901 in BBF!)
GenBank/UNITE ITS = MT967349 / UDB033382.
UNITE SH1526143.08FU.
Misinterpretations:
= Pleurotus tremulus (Schaeff.) P. Kumm., Führ.
Pilzk. (Zerbst): 105 (1871). sensu Fries, Gillet, Cooke,
Quélet, Saccardo, Rea, Pilát, J. Favre, Lange
Pleurotellus tremulus (Schaeff.) Konrad &
Maubl., Encyclop. Mycol. (Paris) 14: 428 (1949)
[1948] sensu Konrad & Maublanc, J. Favre, Kühner
& Romagnesi
Leptoglossum tremulum (Schaeff.) Singer
sensu Singer, Moser
Hohenbuehelia tremula (Schaeff.) Thorn & G.
L. Barron sensu Thorn & Barron, Consiglio.
M a c r o m o r p h o l o g y . – Basidiomata up to
25 × 25 mm, with eccentric to lateral rudimentary
stipe, at times forming complex multilobular or
polycephalic structures up to 30 × 30 mm, with
4–15 mm wide soft lobes or pilei proliferating in all
directions, occasionally hymenium appearing on
the superior pileal surface. Pileus rugulose, soft,
1.5 mm thick near stipe, thinning toward margin,
pruinose, with ne 0.1–0.3 mm long white tomen-
Sydowia 73 (2021) 155
Voitk et al.: The Arrhenia acerosa complex
tum becoming dense near stipe; translucently stri-
ate; concentrically hygrophanous, resulting in a
zonate aspect during drying; initially dark grey-
brown (10YR 4/2-4/3), margin paler (10YR 5/3), be-
coming light grey-brown when dry (10YR 7/3-8/3);
barely darker with 5 % KOH. Lamellae long decur-
rent, straight, occasionally forked; with time and in
complex basidiomata becoming wavy, narrow
(about 1–1.5 mm), crowded, with numerous lamel-
lulae; grey-brown, a little lighter than context
(10YR 5/3), edge entire, concolorous. Stipe initially
broad and short, covered with white tomentum as
on pileus; in complex structures reduced to a barely
differentiated mass, only a few millimetres high, its
upper part covered by decurrent lamellae, and low-
er part by white tomentum, which may partially
cover the base of the hymenium; grey. Context dark
grey (10YR 4/2), very aeriferous throughout, light-
ening when drying; distinct Pelargonium smell and
taste. Spore-print white.
M i c r o m o r p h o l o g y . – Basidiospores (5 ba-
sidiomata, 5 collections, 2 observers, n = 90),
(4.8)5.7–7.0(7.8) × (4.3)5.0–6.3(6.7) µm, average 6.5 ×
5.5 µm; Q = 1.1–1.3, Qavg 1.3; pip-shaped to subglo-
bose, with prominent apiculus reaching 1 µm, hya-
line, smooth, inamyloid, acyanophilous. Basidia
23–35 × 6–8 µm, clavate, 4-spored, sterigmata arched
3–4 µm long. Subhymenial hyphae branched. La-
mellar edge fertile. Cystidia absent; some narrow or
appendiculate sterile marginal hairs observed. Hy-
menophoral trama entangled, aeriferous, made of
richly branched and anastomosed hyphae with
membranal pigment forming dark grey-brown fair-
ly homogeneous patches, irregularly distributed.
Pileipellis loose, not gelatinized, with many more or
less ascending, cylindrical, 4–8 µm wide, wavy hy-
phae, with endings quite frequently lobed; in hir-
sute parts endings fairly dense, well-dened, more
elongated and narrower (× 3–4 µm), exceeding
100 µm, with brown pigmented wall, nely incrust-
ed, in some places with granular, refracting, yellow-
brown intracellular pigment; subcutis undifferenti-
ated. Pileitrama of branched hyphae, 3–10 µm wide,
with brown incrusted membranal pigmentation.
Basal mycelium consisting of cylindrical parallel
and sparsely branched hyphal bundles, 2.5–5 µm
wide, with 80–200 µm spaced septa, with slightly
thickened wall (to 0.5 µm), devoid of crystals. Clamp
connections at base of basidia and abundant in all
tissues.
H a b i t a t . – Growing in both alpine settings
and lowlands, but in more sheltered wooded or open
grassy areas. Terricolous, gregarious, on cottony
mycelium mantles encompassing living stems of
pleurocarpous mosses [e.g. Hylocomnium splendens
(Hedw.) Schimp. and Pleurozium schreberi (Willd.
ex Brid.) Mitt., leaves of surrounding grasses, and
surrounding litter.
D i s t r i b u t i o n . – Known from Europe and
North America. The only acerosa-like species in NL,
to date.
Additional collections studied.
CANADA. NL. Gros Morne National Park, McKen-
zie’s Brook, 49.433318° N, 57.875591° W, 7 m a.s.l.,
with moss in eld by mixed forest, 11 September
2014, leg. Renée Lebeuf, GM15a-995, DAOM-
981251. Gros Morne National Park, McKenzie’s
Brook, 49.433318° N, 57.875591° W; 7 m a.s.l., with
moss and grass in coniferous forest, 11 September
2014, leg. Renée Lebeuf, GM14a-218, DAOM-
981254. Gros Morne National Park, Killdevil camp-
grounds, 49.454057° N, 57.751518° W, 26 m a.s.l.,
among moss in eld beside coniferous forest, 9 Sep-
tember 2014, Renée Lebeuf, GM14a-028, DAOM-
981252. Lockston Path Provincial Park,
48.458148° N, 53.456510° W, 119 m a.s.l., on moss in
coniferous woods, 28 September 2012, leg. Marian
Wissinck, TN3-042, DAOM-981255. Labrador, Hap-
py Valley Ski Club, Robin trail, 53.43266° N,
60.38006° W, on soil under Picea in coniferous
woods, 10 September 2016, leg. Emily Hildebrand,
GBHV16A-429, DAOM-981253. Labrador, Makko-
vik Bay, 55.096939° N, 59.180469° W, 62 m a.s.l.,
among moss and lichens in coniferous woods, 1 Au-
gust 2010, leg. Aare Voitk, 10.08.01.av03, (specimen
lost in mail). ESTONIA. Hiiu Co., Kõpu peninsula,
58.9387° N, 22.27957° E, in coniferous forest, 14 Oc-
tober 2014, leg. Vello Liiv, TU-120029. NORWAY.
Hordaland, Bømlo, Otterøya, 59.7251° N, 5.4333° E,
on moss in natural meadow, 1 October 2009, leg. As-
björn Knutsen, John Bjarne Jordal, O-291235.
C o m m e n t s . – Except when it reaches the
orid, multicephalic state, it may be macroscopi-
cally indistinguishable from several members of the
A. acerosa group; other species have broad subglo-
bose spores, but the relatively uniform subglobose
shape can be helpful for indentication. In a com-
plex of many parochial species, A. subglobisemen
seems phylogenetically stable across at least two
continents, like the circumpolar Lichenomphalia
umbellifera (Geml et al. 2012a).
Arrhenia svalbardensis
Gulden, I. Saar & Lücking,
sp. nov. – Figs. 3F–G, 6H–I
MycoBank no.: MB 836885
Ty p i f i ca t io n . – Holotypus: NORWAY. Sval-
bard, Isfjord distr., Hotelneset, N of the airport,
156 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
with Salix polaris and Dryas octopetala, 14 August
1986, leg. Gro Gulden & Kolbjørn Mohn Jenssen,
GG 411/86, O-50446. GenBank/UNITE ITS =
MT967358 / UDB024589. UNITE SH1526148.08FU.
Etymology. – Svalbardensis refers to Sval-
bard, where the species was discovered and is quite
common.
D i a g n o s i s . – Brown-grey basidiomata, pilei
under 25 mm diam, pleurotoid, with or without a
lateral stipe under 2.5 mm long, 2- or 4-spored,
growing in arctic heaths. Distinguished from other
members of the complex by larger spores and ITS
sequence data.
Holotype collection. – Three small ba-
sidiomata and some fragments, one apparently of a
short stipe. Pilei dry, semiorbicular, up to 7 mm
wide with incurved margin and a smooth, dark grey
brown surface. Lamellae rather distant and narrow,
dark grey. A short, cylindrical, solid, lateral stipe,
up to 1.5 mm, pale grey and basally white tomen-
tose in one specimen, lacking in others. Basidia 25–
30 × 7.3–8.0(8.7) µm, 4-spored, with walls becoming
± brown with age. Basidiospores (1 basidioma,
1 collection, 1 observer, n = 30) 7.8–10.6 × 4.3–6.3 µm,
Q = 1.3–2.2, Qavg = 1.7, broadly elliptical to slightly
lacrymoid, hyaline, inamyloid, acyanophilous. Cys-
tidia absent. Hymenophoral trama made of ca
4–10 µm wide hyphae, ± brown. Pileipellis a cutis
made of radial, 4–10 µm wide, medium celled hy-
phae, ± zebroid. Clamp connections at base of ba-
sidia and throughout all tissues. Pigment membra-
nal and incrusting.
Macromorphology. – Pileus 522 mm,
semiorbicular, fan-shaped, thin-eshed, incurved
with white pubescent margin when young, becom-
ing straight to reexed and ± crenulate to lobed, de-
pressed at stipe attachment; white pubescent in
youth, gradually becoming smooth except at stipe
attachment, where a white tomentum often persists,
matte to slightly greasy, azonate, not striate, hy-
grophanous, evenly dark olive brown to dark grey
brown (T51, T71), drying to grey brown or pale grey
with a tinge of yellow (N50, P67, 69, M70, L90). La-
mellae adnexed to decurrent, subdistant to distant,
occasionally forked or with 1–3 lamellulae, up to
1.5 mm high, thin to slightly thickened, grey ±like
the pileus (P91, 92). Stipe, if present, up to 2.5 mm
long, 1–2.5 mm thick, lateral to central, cylindrical
or somewhat tapering downwards, solid, white pu-
bescent. Context pale grey in pileus centre, dark
grey in stipe cortex. No particular smell noted; taste
not tested.
M i c r o m o r p h o l o g y . – Basidiospores, 4-spored
(4 basidiomata, 4 collections, 1 observer, n = 60) 7.8–
10.6(12.6) × 4.3–6.3 µm, Q = 1.3–2.2, Qavg = 1.7;
2-spored (1 basidioma, 1 collection, 1 observer, n =
17) 9.7–18(23) × 6.3–8.0(9.5) µm, Q = 1.3–2.3, Qavg =
1.8; elliptical to slightly lacrymoid, blunt, with
prominent apiculus, hyaline, smooth, inamyloid,
acyanophilous. Basidia 25–30 × 7.3–8.0(8.7) µm,
4-spored basidiomata; 30–41 × 6.8–10 µm,
(1)2-spored basidiomata. Cystidia absent. Hyme-
nophoral trama made of ca 3–10 µm wide, ± brown
incrusted hyphae. Pileipellis a cutis made of radi-
ally repent, 3–10 µm wide, cylindrical, thin-walled,
± brown incrusted hyphae. Stipitipellis made of
thin-walled, cylindrical or inated 2–22 µm wide
hyphae, evenly brown or zebroid; tomentum at base
of stipe made of cylindrical, thin-walled, hyaline
hyphae, 2.5–5 µm wide. Dermatocystidia absent.
Clamp connections present at base of basidia and
throughout all tissues. Pigment membranal and in-
crusting.
H a b i t a t . – On almost bare soil and among
moss in arctic heath vegetation with Salix polaris
and Dryas; autumn.
D i s t r i b u t i o n . – Sporadic in Svalbard, but
not the only species there (see Comments). Con-
rmed by environmental sampling (KC966345)
from Prince Patrick Island in the Northwest Terri-
tories of Canada.
Additional collections studied.
NORWAY. Svalbard. Gluudneset, with Salix polaris
and Dryas octopetala, 12 August 1988, leg. Gro Gul-
den, GG31/88, O-195466. Ny-Ålesund, near the
Cambridge lab, in yard with moss and Salix polaris,
4 August 1986, leg. Gro Gulden, Kolbjørn Mohn
Jenssen, GG159/86, O-50444. Endalen, W side, on
bare soil in a depression, 10 August 2015, leg. Sten
Svantesson, GG25/15, O-76070.
C o m m e n t s . – Description based on notes of
fresh material from O-50446, O-76070, O-195466
(4-spored), and O-50444 (2-spored). The latter has
been described with a photograph by Gulden &
Jenssen (1988). A single basidioma of the similar
AC-7 (O-50445) comes from a bird-cliff habitat in
Svalbard. It has a short eccentric stipe and large
spores in the range of A. svalbardensis, 8.7–10.6(12.6)
× 4.8–6.8, Qavg = 1.8 (n=20).
Arrhenia tillii
(Krisai & Noordel.) Krisai & I. Saar,
comb. nov. – Figs. 2J, 6J
MycoBank no.: MB 836886, UNITE SH2713468.08FU.
Rhodocybe tillii Krisai & Noordel., Öst. Z.
Pilzk. 7: 264 (1998) (basionym)
Clitopilus tillii (Krisai & Noordel.) Noordel. &
Co-David, Persoonia: 23: 164. 2009
Sydowia 73 (2021) 157
Voitk et al.: The Arrhenia acerosa complex
Fig. 6. Line drawings of spores and basidia of treated species, in alphabetical order. Bar 10 µm for all. A. Neotype for Arrhenia
acerosa s. str., UPS-F151993. B. Holotype for A. fenicola, UWO-F44. C. Epitype for A. glauca, WU-6564. D. Holotype for A. jun-
corum, LIP-0401674. E. Epitype for A. latispora, LIP-0401569. F. Holotype for A. leucotricha, BBF-CH13091220. G. Epitype for
A. subglobisemen, BBF-GC15100901. H. Holotype for A. svalbardensis, O-50446, 4-spored collection. I. 2-spored collection of A.
svalbardensis, O-50444. J. Holotype for A. tillii, WU-18120.
158 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
Misinterpretations:
Pleurotus roseolus Quél. Bull. Soc. Amis Sci.
Nat. Rouen, Sér II:15: 155. (1879)1880
Arrhenia roseola sensu Senn-Irlet 1986
(≡Phaeotellus roseolus (Quél:) Horak 2005;
Pleurotellus roseolus (Quél.) Kühner, based on
Pleurotus roseolus Quél.)
Comment. Arrhenia tillii differs from AC-3
(Fig. 4B1–2) by a rudimentary or lacking stipe, lateral
attachment, pink sporeprint and coniferous sub-
strate. Additional nds of Arrhenia tillii in France
and Switzerland share the same substrate (Pinus
nigra) as the Austrian collections (Senn-Irlet 1986,
Francini 2000). A pink specimen from Quebec (Ac-
5, Fig 4G; Lamoureux 2015), identied as Clitopilus
tillii, proved to be quite distant in the ITS tree (see
discussion). The subglobose, obovoid to broadly el-
liptical spores make a striking discriminating char-
acter of A. tillii: seemingly smooth under the light
microscope, but pustular-wavy in lateral and slight-
ly angular-wavy in pole view with a large hilar api-
culus under SEM, characters that previously led to
its inclusion in the former genus Rhodocybe. Gröger
(2006) also suspected parasitic growth on liver-
worts, which is not the case with the Austrian nd-
ings.
Discussion
All but one of our aims were met. We conrmed
that the Arrhenia acerosa-like species native to NL
is A. subglobisemen, typied the name with a se-
quenced specimen, and circumscribed the species.
We were fortunate to nd a suitable collection to
neotypify and circumscribe A. acerosa s. str. We
agree with Redhead (1984) that Batsch’s (1786) pro-
tologue for A. glauca ts Arrhenia acerosa (or at
least a species in the acerosa complex), and lecto-
typied the illustration. The habitus of Arrhenia lo-
bata, A. spathulata and A. auriscalpium may resem-
ble that illustration somewhat, but all have a re-
duced hymenium with sinuous, forked ridges joined
by smaller anastomosing intervenose ridges, where-
as Batsch’s illustration clearly shows sharp, straight,
unforked lamellae. Through good fortune we found
a collection morphologically matching the lecto-
type from the same habitat and region, enabling us
to epitypify A. glauca. The good t with a robust
modern collection seemed like too good an opportu-
nity for preserving Batsch’ epithet to miss. One of
our more gratifying results was the ability to secure
the concept of A. latispora. Likely, mycologists un-
familiar with the species, living outside its range,
have been misled by the stress on spore width in the
epithet and protologue, a character we now know to
be common to many species in the acerosa complex,
causing them to synonymize these with A. acerosa.
Once discrete well-supported clusters developed
in our phylogenetic tree, authors familar with some
were able to recognize them as distinct species. For
example, A. svalbardensis with its wide spores was
familiar to one of us from repeated study, and A.
fenicola had been studied formally in the course of
an MSc project (Hay 2016) by both student and su-
pervisor. An additional consideration for describing
A. fenicola now was that it seems to be restricted to
unpopulated Canadian prairieland, a region not
studied as commonly by mycologists as the Alps,
central Europe and Scandinavia. Others among the
author group recognized as discrete species the
clades now bearing the names A. juncorum and A.
leucotricha.
To us, far more signicant than the treatment of
nine taxa or description of four new ones, was the
discovery of an unexpected number of undescribed
species to which the name Arrhenia acerosa has
been applied in the past. These and some other
questions raised by our enquiry are left for future
investigations. This includes our circumscription of
the species we have treated. As with most rst in-
vestigations, our limited experience may have made
our circumscriptions overly narrow (e.g. A. tillii, A.
leucotricha), or overly wide (e.g. A. glauca); more
experience, coupled to more denitive technology
may nd that lumping some species and splitting
others is more appropriate.
The only aim we were unable to meet was to cir-
cumscribe A. acerosa va r. tenella s. str. Sterigma
count did not seem to correlate with phylogenetic
ranking for A. svalbardensis, but we are unable to
say whether this applies to A. acerosa var. tenella.
When Aronsen (1992) transferred P. acerosa va r.
tenella to Arrhenia he based his description on
three 2-spored Norwegian collections growing on
Juncus, not type material for A. acerosa var. tenella.
One of these specimens, resembling A. juncorum
but distant from it phylogenetically, is in our tree
(G-1, O-65097), and it would be tempting to typify
the taxon with that collection, but Kühner’s lecto-
type was collected in Algeria, differing signicantly
in climate and habitat from Norway. In view of the
diversity and parochial nature of species in the ace-
rosa complex, it seems more prudent to leave secur-
ing of the name tenella to future investigations.
Despite having robust herbarium specimens,
good photos (Fig. 4) and/or collecting notes, micro-
scopic ndings and phylogenetic ranking for some
potential species, we lack sufcient experience with
Sydowia 73 (2021) 159
Voitk et al.: The Arrhenia acerosa complex
them as separate entities with unique appearance
and behaviour in their own environment to be able
to describe them as distinct organisms among their
peers. Future observations to gain sufcient knowl-
edge of them in their habitat, as well as denitive
resolution of all phylogenetic nodes with multilocus
analysis, are bound to be rewarded by the descrip-
tion of several new speies. Figure 1b is our attempt
to correlate ranking with characters gleaned retro-
spectively from records accompanying the studied
collections. Records may be erroneous and observa-
tions fortuitous or skewed. For example, it is easy to
omit or include soil, earth, bryophytes or duff be-
cause these are virtually omnipresent in most habi-
tats where species in this complex are found. Clear-
ly, this character list is only a modest beginning, to
be rened or replaced by more detailed observation,
as more experience with these species accumulates.
At the end of this Discussion section, we provide a
preliminary key for the pleurotoid species. Like the
character list, this is a preliminary attempt, which
should be improved with more experience with this
diverse group.
One of the interesting projects that may come
from this work is the study of pink-spored, pink
species within this white-spored grey to brown ge-
nus. That the pink Clitopilus tillii turned out to be a
species of Arrhenia should not have been entirely
unexpected, because pink species have been re-
ferred to the genus in the past. (As mentioned in the
introduction, we consider roseola misapplied to a
pink species of Arrhenia). Krieglsteiner (2011) re-
ports two sites for a pink acerosa-like species, one
near Schweinfurt, Germany, on a species of Molinia
on calcareous soil in a dry warm area, and the other
near Bachaue, Germany, on Phalaris arundinaceae.
If these species are substrate specic, then gramini-
colous collections may differ from the Austrian A.
tillii on coniferous wood. AC-3, a French terricolous
collection identied earlier as A. roseola”, falls in
proximity to A. tillii in our tree, suggesting that
they may be closely related, but the substantial dif-
ferences in the ITS do not allow treating them as
conspecic. The North American pink species, AC-
5, is quite remote from A. tillii, another example of
homoplasy in this complex.
Molecular genetic studies revealed that in addi-
tion to the diverse morphology of the pleurotoid
habitus, the omphalinoid habitus has found repeat-
ed expression in the cascading acerosa complex
throughout a wide geographic range, so far docu-
mented from both Hemispheres, four continents
and eight countries. In our current tree these are
found in G-2, a group of 4-spored basidiomata, and
G-3, a group containing both 2- and 4-spored ba-
sidiomata. Many of these specimens were identied
as A. griseopallida (Desm.) Watling, but the epithet
was also applied to several pleurotoid collections,
suggesting a very varied interpretation of the name.
Kühner & Lamoure (1972) observed that the stipe
of P. acerosus starts centrally, soon ceases to elon-
gate, and because of inequilateral growth, ends up
eccentric or lateral. Such transition from a central
to lateral stipe within the acerosa complex was not-
ed in A. svalbardensis, and is suggested by compar-
ing the collection from northern Québec (Fig. 5C)
and A. subglobisemen in Fig. 2G. The thick stipe
and incomplete pileus of at least one Québec ba-
sidioma approaches the pleurotoid habitus and lat-
eral stipe of the latter. Study of these omphalinoid
species of the acerosa complex is an interesting and
signicant project, requiring, among other things,
typication of A. griseopallida and study of its rela-
tionship to the acerosa complex.
Most species of the acerosa complex seem to be
parochial. So far, A. subglobisemen seems to have a
wide distribution across two continents; A. sval-
bardensis has also been recorded from two conti-
nents, but the seriously understudied Canadian
north may hide further contributions to this com-
plex. In addition to very varied morphology, habitat
and distribution preferences, collecting records in-
dicate this group also occupies diverse substrates. A
few are recorded to grow on bare soil or gravel, and
a small number are noted to have an apparent as-
sociation with bryophytes, generally thought to be
the lifestyle for arrhenias. The majority is docu-
mented to grow on rotten deciduous and coniferous
wood, wood chips, conifer duff, herbaceous litter
(including live or dead Ammophila, Juncus and
Carex), peat and herbivore dung (horse, sheep, and
reindeer have been recorded). Signicantly, most
wood-associated collections do not grow on large
boles of rotten wood, which may be acting as water
banks rather than nutritional substrate, but chips
(Figs. 4A, C) or small debris, often with no visible
bryophytes on them, as is seen with true lignicolous
species. This preponderance of woody or herba-
ceous substrates suggests a saprobic lifestyle with
an afnity for a cellulose-containing material, rath-
er than the moss-association generally accepted for
species of Arrhenia. Elucidating the lifestyle of the
members of this complex seems like another worth-
while undertaking.
We have raised far more questions than we have
answered. The answers to most of these, including
the placement of Pilát’s (1935) and Velenovský’s
(1920, 1927) taxa, lie outside the scope of this study
160 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
or outside our ability at this time. It is our hope that
awareness of these questions will promote produc-
tive future investigations.
Tentative key to pleurotoid members of the
Ar-
rhenia acerosa
complex
1. a) Basidiomata pink or pinkish ....................... 2
1. b) Basidiomata without pink tones; white or
pale, grey, brown or violaceous ........................ 4
2. a) Fruiting on rotted coniferous wood, some-
times with bryophytes; central Europe ..............
........................................................Arrhenia tillii
2. b) Fruiting on soil, sometimes with bryophytes;
Europe or North America ................................. 3
3. a) Arcto-alpine, in central Europe .............. AC3
3. b) In temperate forests, North America ...... AC5
4. a) Basidiomata large (2–3 cm broad), dark viola-
ceous; lower alpine zone in Europe; on soil, of-
ten with bryophytes, basidiospores large, 7.8–
9.5 × 6.3–6.8 µm .................... Arrhenia latispora
4. b) Basidiomata smaller and not violaceous .... 5
5. a) Basidiospores broad (Qavg < 1.5), pip-shaped
to subglobose, 5.7–7.0 × 5.0–6.3 µm; basidioma-
ta grey to grey-brown; on soil or associated with
bryophytes or herbaceous litter in mixed forests
or grasslands, Europe and North America .........
...................................... Arrhenia subglobisemen
(if basidiospores plump but most less than 5 µm
broad, see A. leucotricha)
5. b) Qavg of basidiospores > 1.5 ............................ 6
6. a) Basidiospores narrowly elliptical to slightly
lacrymoid, 6.8–8.7 × 3.4–3.9 µm; basidiomata
grey-brown, on soil or wood in north Europe .....
......................................... Arrhenia acerosa s.str.
6. b) Basidiospores broader, many > 4 µm broad .7
7. a) Most basidiospores > 5 µm broad, 7.7–10.7 ×
4.8–6.8 µm (4-spored; broader in 2-spored); in
Svalbard and the Canadian arctic; basidiomata
grey-brown to brown ... Arrhenia svalbardensis
(if some basidiospores broader than 5 µm but
habitat in North American grasslands, see A.
fenicola)
7. b) Most basidiospores < 5 µm broad ................ 8
8. a) On soil or associated with grass or herba-
ceous litter in North American grasslands ........
..................................................Arrhenia fenicola
8. b) European; habitats various ...........................9
9. a) Basidia consistently 2–spored; basidiospores
6–9 × 3.6–5.1 µm; basidiomata on various sub-
strates and varied habitats in central and north-
ern Europe ...................................................... G1
9. b)
Basidia 4–spored or occasionally 2–spored
10
10. a) Fruiting on soil or wood debris in woodland
or grassland (mesic) habitats; basidiomata dis-
tinctly pale blue-grey, white-tomentose; lamel-
lae greyish; pseudostipe white-tomentose ..........
.................................................. Arrhenia glauca
10. b) Fruiting in wetland habitats ...................... 11
11. a) Fruiting directly on dead leaves of wetland
graminoids .......................... Arrhenia juncorum
11. b) Fruiting on wet organic soil in montane or
arcto-alpine habitats ...........................................
............................................ Arrhenia leucotricha
Acknowledgements
We thank Carole Hannoire (BBF), Raymond Ar-
chambault (CMMF), Philippe Clerc (G), Ellen Lars-
son (GB), Régis Courtecuisse (LIP), Katriina
Bendiksen (O), Kadri Pärtel (TAAM), Stefan Ekman
(UPS), Walter Till (WU), and Sven-Åke Hanson for
the loan of specimens; Ellen Larsson and Renée
Lebeuf & Jacques Landry for contributing and se-
quencing specimens for this study; Arne Aronsen,
Sven-Åke Hanson, Anton Hausknecht, Kolbjørn
Mohn Jenssen, Jacob Kalichman, Wolfgang Klofac,
Yves Lamoureux, Renée Lebeuf, Vello Liiv, Per
Marsted, Pierre Roux, Matthew Smith, Anita & Leif
Stridvall and Marcel Vega for the use of their photo-
graphs; and Joe Brazil for help rescuing a verisi-
militudinous image from stubborn slides; Nicholas
Turman for nomenclatural advice; Jason Karakehi-
an, Machiel Noordeloos and Fermín Pancorbo for
bibliographic help; Kesiban Özdemir for sequenc-
ing help; the Austrian Ministry of Science for fund-
ing the Austrian Barcoding Project ABOL; and one
anonymous reviewer for a critical reading of the
manuscript to strengthen its presentation. Irja Saar
was supported by the Estonian Research Council
(IUT20-30), and the European Regional Develop-
ment Fund (Centre of Excellence EcolChange).
References
Albertini I.B. von, Schweinitz L.D. von (1805) Conspectus fun-
gorum. Kummer, Leipzig.
Aronsen A. (1992) Hemimycena subglobispora, spec. nov., and
Arrhenia acerosa va r. tenella, comb. nov., from wetlands in
southern Norway. Persoonia 14: 425–429.
Barrasa J.M., Rico V.J. (2003) The non-omphalinoid species of
Arrhenia in the Iberian Peninsula. Mycologia 95: 700–713.
Batsch A.J.K. (1786) Elenchus fungorum. Continuo prima. T24,
p. 169, Pl 123.
Blanco-Dios J.B. (2019) Notes on genus Arrhenia (I): Arrhenia
pontevedrana, sp. nov. and A. subglobisemen (Agaricales,
Basidiomycota), from the northwest of the Iberian Penin-
sula. Studies in Fungi 4: 185–191. Doi 10.5943/sif/4/1/20.
Bolton J. (1788). An History of funguses growing about Hali-
fax. Author, Halifax.
Bon M., Chevassut G. (1988) Contribution à l’étude de la mac-
roore fongique et sabulicole du littoral méditerranéen.
Documents mycologiques 18(72): 51–61.
Sydowia 73 (2021) 161
Voitk et al.: The Arrhenia acerosa complex
Bon M., Courtecuisse R. (1987) Espèces ou combinaisons nou-
velles et validations de taxons. Documents mycologiques
18(70–71): 37.
Bueno de Mesquita C.P., Sartwell S.A., Ordemann E.V., Po-
razinska D.L., Farrer E.C., King A.J., Spasojevic M.J.,
Smith J.G., Suding K.N., Schmidt K.S. (2018) Patterns of
root colonization by arbuscular mycorrhizal fungi and
dark septate endophytes across a mostly-unvegetated,
high-elevation landscape. Fungal Ecology 36: 63–74.
Bueno de Mesquita C.P., Sartwell S.A., Schmidt S.K., Kathar-
ine N. Suding K.N. (2020) Growing season length and soil
microbes inuence the performance of a generalist bunch-
grass beyond its current range. Ecology 101(4): e03095. doi.
org/10.1002/ecy.3095 and Bulletin of the Ecological Soci-
ety of America 101(4):e01743. doi.org/10.1002/bes2.1743
Cailleux A. (1981) Code des couleurs des sols. Boubée, Paris.
Co-David D., Langeveld D., Noordeloos M.E. (2009) Molecular
phylogeny and spore evolution of Entolomataceae. Persoo-
nia 23: 147–176.
Consiglio G. (2016) Nomenclatural novelties. Index Fungorum
no. 292. http://www.indexfungorum.org/Publications/
HTML/Index%20Fungorum292.html.
Corriol G. (2016) Arrhenia subglobisemen, un nouveau nom
pour Agaricus tremulus sensu Persoon, Fries. Bulletin my-
cologique botanique Dauphiné-Savoie 222: 5–20.
Courtecuisse R. (2008) Novitates. 5. Nouvelles combinaisons et
nouveaux noms nécessaires suite à la mise au point du ré-
férentiel des noms de champignons présents sur le terri-
toire national métropolitain (1 - Basidiomycètes). Docu-
ments Mycologiques 34(135–136): 48–52.
Doassans E., Patouillard N. (1886) Champignons du Béarn.
Revue Mycologique de Toulouse 8: 25–28 (26).
Elborne S.A. (2008). Arrhenia Fr. In: Knudsen H., Vesterholt J,
eds: Funga Nordica, Nordsvamp, København, p. 913.
Favre J. (1955) Les champignons supérieures de la zone alpine
du Parc National Suisse, Ergebnisse der Wissenschaftli-
chen Untersuchungen des Schweizerischen Nationalparks
5: 1-212.
Francini L. (2000) Rhodocybe tillii Krisai & Noordel. francini-
mycologie.fr [accessed July 18, 2019].
Fries E.M. (1821) Systema mycologicum 1: 1–520(191). Berlin-
giana, Lund.
Fries E.M. (1828) Elenchus Fungorum. E. Mauritius. Grief-
swald.
Fries E.M. (1849) Summa vegetabilium 2: 1–572(312). Bonnier,
Uppsala.
Fries E.M. (1874a) Icones selectae Hymenomycetum. 1. Hol-
miae, Uppsala.
Fries E.M. (1874b) Hymenomycetes Europaei. Ed. Berling,
Uppsala.
Geml J., Kauff F., Brochmann C., Lutzoni F., Laursen G.A.,
Redhead S.A., Taylor D.L. (2012a) Frequent circumarctic
and transequatorial dispersals in the lichenized agaric ge-
nus Lichenomphalia (Hygrophoraceae, Basidiomycota).
Fungal Biology 116: 388–400.
Geml J., Timling I., Robinson C.H., Lennon N., Nusbaum H.C.,
Brochmann C., Noordeloos M.E., Taylor D.L. (2012b) An
arctic community of symbiotic fungi assembled by long-
distance dispersers: phylogenetic diversity of ectomycor-
rhizal basidiomycetes in Svalbard based on soil and spo-
rocarp DNA. Journal of Biogeography 39(1): 74–88.
Gröger F. (2006) Bestimmungsschlüssel für Blätterpilze und
Röhrlinge in Europa Teil 1. Regensburger Mykologische
Schriften 13.
Gulden G. (1980) Alpine Galerinas (Basidiomycetes, Agari-
cales) with special reference to their occurrence in South
Norway at Finse on Hardangervidda. Norw. J Bot. 27: 219-
253.
Gulden G., Jenssen K.M. (1988) Arctic and Alpine fungi
2. Soppkonsulenten, Oslo.
Hahn, C., Friebes, G., Krisai-Greilhuber, I., (2018) Sarcodon
fennicus, a boreo-montane stipitate hydnoid fungus with a
remarkable smell. Österreichische Zeitschrift für Pilz-
kunde 27: 43–52.
Hanson S.-Å. (2017) Koprola svampar i Skåne, speciellt I
östra Skånes sandmarker—arter på spillning av nötkrea-
tur. Svensk Mykologiskt Tidskrift 38(2): 8–22.
Hay C. (2016) Agaricomycetes of Ontario tallgrass prairies.
Electronic thesis and dissertation depository. 3995. ht-
pps://ir.lib.uwo.ca/etd/3995.
Hesler R.L. (1967) Entoloma (Rhodophyllus) in southeastern
North America. Beihefte zur Nova Hedwigia 28: 1–220.
Karich A., Kellner H., Schmidt M., Ullrich R. (2015) A remark-
able mycotope in the Zittau Mountains with the rst re-
cord of Microglossum rufescens in Germany. Boletus 36:
151–163.
Kõljalg U., Nilsson H., Abarenkov K., Tedersoo L., Taylor
A.F.S., Bahram M., Bates S.T., Bruns T.T., Bengtsson-Palme
J., Callaghan T.M., Douglas B., Drenkhan T., Eberhardt U.,
Dueñas M., Grebenc T., Grifth G.W., Hartmann M., Kirk
P.M., Kohout P., Larsson E., Lindahl B.D., Lücking R.,
Martín M.P., Matheny P.B., Nguyen N.H., Niskanen T., Oja
J., Peay K.G., Peintner U., Peterson M., Põldmaa K., Saag
L., Saar I., Schüßler A., Scott J.A., Senés C., Smith M.E.,
Suija A., Taylor D.L., Telleria M.T., Weiß M., Larsson K.-H.
(2013) Towards a unied paradigm for sequence-based
identication of Fungi. Molecular Ecology 22(21): 5271–
5277.
Kornerup A., Wanscher J.H. (1978) Taschenlexikon der Farben.
3rd edn. Zürich, Göttingen, Muster-Schmidt.
Krieglsteiner L., (2011) Pilzfunde im Nationalpark Eifel I –
2011. http://www.pilzkunde.de/images/pdf/Eifel%20Gu-
tachten%202011.pdf [accessed July 18, 2019]
Krisai-Greilhuber I., Noordeloos E.M. (1998) Rhodocybe tillii,
a conchate new species found in Austria. Österreichische
Zeitschrift für Pilzkunde 7: 263–268.
Kühner R. (1954) Compléments à la Flore analytique, III.
Éspèces nouvelles, critiques ou rares de Pleurotacées,
Marasmiacées et Tricholomacées. Bulletin de la Société
des naturalistes d’Oyonnax 8: 73–131(76).
Kühner R. (1980) Les hyménomycètes agaricoïdes (Agaricales,
Tricholomatales, Pluteales, Russulales). Étude général et
classication. Numéro Spécial du Bulletin de la Société
Linnéenne de Lyon 49: 1–1027.
Kühner R., Lamoure D. (1972) Agaricales de la zone alpine,
Pleurotacées. Botaniste 55: 7–37.
Kuhnert R., Oberkoer I., Peintner U. (2012) Fungal growth
and biomass development is boosted by plants in snow-
covered soil. Microbial Ecology 64(1): 79–90.
Kummer P. (1871) Der Führer in die Pilzkunde (p. 105). E.
Luppe, Zerbst.
Kuyper T.W. (1995) Arrhenia. In: Bas C., Kuyper T.W.,
Noordeloos M.E., Vellinga E.C., eds: Flora Agaricina Neer-
landica 3: 77–88.
Lamoureux Y. (2015) Rhodocybe tillii. mycoquebec.org [ac-
cessed January 28, 2020].
Lange J.E. (1936) Flora Agaricina Danica. 2: p. 71; pl. 63B.
København.
162 Sydowia 73 (2021)
Voitk et al.: The Arrhenia acerosa complex
Larsson K.H. (2007) Re-thinking the classication of corti-
cioid fungi. Mycological Research 111: 1040–1063.
Lawrey J.D., Lücking R., Sipman H.J.M., Chaves J.L., Redhead
S.A., Bungartz F., Sikaroodi M., Gillevet P.M. (2009) High
concentration of basidiolichens in a single family of aga-
ricoid mushrooms (Basidiomycota: Agaricales: Hy-
grophoraceae). Mycological Research 113: 1154–1171.
Le Breton A., Quélet L. (1879) Champignons récemment ob-
servés en Normandie, aux environs de Paris et de La Ro-
chelle, en Alsace, en Suisse et dans les montagnes du Jura
et des Vosges. Bulletin de la Société des Amis des Sciences
Naturelles du Musée de Rouen 15: 153–184.
Lodge D.J., Padamsee M., Matheny P.B., Aime M.C., Cantrell
S.A., Boertmann D., et al. (2014) Molecular phylogeny,
morphology, pigment chemistry and ecology in Hy-
grophoraceae (Agaricales). Fungal Diversity 64: 1–99.
Lücking R., Thorn R.G., Saar I., Piercey-Normore M.D., Mon-
cada B., Doering J., Mann H., Lebeuf R., Voitk M., Voitk A.
(2017) A hidden basidiolichen rediscovered: Omphalina
oreades is a separate species in the genus Lichenomphalia
(Basidiomycota: Agaricales: Hygrophoraceae). The Li-
chenologist 49: 467–481.
Marciulynas A., Marciulyniene D., Lynikiene J., Gedminas A.,
Vaiciukyne M., Menkis A. (2020) Fungi and oomycetes in
the irrigation water of forest nurseries. Forests 11: 459;
doi:10.3390/f11040459www.mdpi.com/journal/forests
Lutzoni F.M. (1997) Phylogeny of lichen- and non-lichen-
forming omphalinoid mushrooms and the utility for test-
ing for combinability among multiple data sets. System-
atic Biology 46: 373–406.
Moncalvo J.M., Vilgalys R., Redhead S.A., Johnson J.E., James
T.Y., Aime M.C., Hofstetter V., Verduin S.J., Larsson E., Bar-
oni T.J., Thorn R.G. (2002) One hundred and seventeen
clades of euagarics. Molecular Phylogenetics and Evolu-
tion 23(3): 357–400.
Munsell Color Co. (2000) Munsell soil color charts. Baltimore,
Munsell Color Company.
Nilsson R.H., Larsson K.-H., Taylor A.F.S., Bengtsson-Palme
J., Jeppesen T.S., Schigel D., Kennedy P., Picard K., Glöck-
ner F.O., Tedersoo L., Saar I., Kõljalg U., Abarenkov K.
(2019) The UNITE database for molecular identication of
fungi: handling dark taxa and parallel taxonomic classi-
cations. Nucleic Acids Research 47(D1): D259–D264.
Oberkoer I., Peintner U. (2008) Detection of soil fungal com-
munities in an alpine primary successional habitat: Does
pooling of DNA extracts affect investigations? Annals of
Microbiology 58: 585–595.
Osmundson T.W., Robert V.A., Schoh C.L., Baker L.J., Smith A.,
Robich G., Mizzan L., Gabrelotto M.M. (2013) Filling gaps
in biodiversity knowledge for macrofungi: contributions
and assessment of an herbarium collection DNA barcode
sequencing project. PLos ONE 8: E62419.
Persoon C.H. (1796) Observationes mycologicae. 1: 8. H. Di-
etrich, Göttingen.
Persoon C.H. (1801) Synopsis methodica fungorum. 2. P. P.
Wolf, Leipzig.
Petersen R.H., Knudsen H. (2015) The mycological legacy of
Elias Magnus Fries. IMA Fungus 6(1): 99–114.
Pilát A. (1935) Pleurotus Fries. In: Kavina C., Pilát A, eds: At-
las des champignons de l’Europe 1, published by the edi-
tors, Praha, 193 p.
Pilát A., Svrcˇek M. (1953) O mensím ousku sivém—Leptotus
glaucus—ve smyslu Batschove—Frieseove a Quelétove i
pozdejsích autoru. C
ˇeská Mykologie. 7: 8–13.
Redhead S.A. (1984) Arrhenia and Rimbachia, expanded ge-
neric concepts, and a reevaluation of Leptoglossum with
emphasis on muscicolous North American taxa. Canadian
Journal of Botany 62: 865–892
Redhead S.A., Lutzoni F., Moncalvo J.M., Vilgalys R. (2002)
Phylogeny of agarics: partial systematics solutions for
core omphalinoid genera in the Agaricales (Euagarics).
Mycotaxon 83: 19–57.
Schäffer J.C. (1774) Fungorum qui in Bavaria et Palatinatu
circa Ratisbonam nascuntur lcones nativis coloribus ex-
pressae 4: 53, t. 224.
Senn-Irlet B. (1986) Zur Ökologie, Soziologie und Taxonomie
alpiner Makromyzeten in der Schweiz. Dissertation an der
Universität Bern.
Thiers B. (2020, continuously updated) Index Herbariorum: a
global directory of public herbaria and associated staff.
New York Botanical Garden’s Virtual Herbarium http://
sweetgum.nybg.org/ih/
Thorn R.G., Barron G.L. (1986) Nematoctonus and the tribe
Resupinateae in Ontario, Canada. Mycotaxon 25: 321–453.
Thorn R.G., Kim J.I., Lebeuf R., Voitk A. (2017) The golden
chanterelles of Newfoundland and Labrador: a new spe-
cies, a new record for North America, and a lost species
rediscovered. Botany 95: 547–560.
Timling I., Walker D.A., Nusbaum C., Lennon N.J., Taylor D.L.
(2014) Rich and cold: diversity, distribution and drivers of
fungal communities in patterned-ground ecosystems of the
North American Arctic. Molecular Ecology 23: 3258–3272.
Truong C., Mujic A.B., Healy R., Kuhar F., Furci, G., Torres D.,
Niskanen T., Sandoval-Leiva P.A., Fernandez N., Escobar
J.M., Moretto A., Palfner G., Pster D., Nouhra E., Swenie,
R., Sánchez-Garcia M., Matheny P.B, Smith M.E (2017)
How to know the fungi: combining eld inventories and
DNA-barcoding to document fungal diversity. New Phy-
tologist 214: 913–919.
Velenovský J. (1920) C
ˇeské Houby. C
ˇeské Botanické
Spolecˇnosti, Praha 2: 201–424.
Velenovský J. (1927) O nových pro C
ˇechy drusich r. Pleurotus
(Hliva) Mycologia 4: 27–34.
Voitk A. (2017) Arrhenia subglobisemen. Omphalina 8(5): 19.
Voitk A., Saar I., Trudell S., Spirin V., Beug M., Kõljalg U. (2017)
Polyozellus multiplex (Thelephorales) is a species complex
containing four new species. Mycologia 109: 975–992.
Watling R. (1989) [1988] Some British omphalinoid and pleu-
rotoid agarics. Notes Royal Botanic Garden Edinburgh
45(3): 549–557.
Zvyagina E.A., Alexandrova A.V., Bulyonkova T.M. (2015) Om-
phalina discorosea: taxonomical position of the species.
Micologia i Phitopathologia 49: 19–25.
(Manuscript accepted 1 November 2020; Corresponding Edi-
tor: J. Nuytinck)
... Arrhenia-species are either obligatory bryophiles, e.g., A. retiruga and A. lobata, others are lichenophiles, e.g., A. peltigerina, still others are not strictly moss-bound at all, such as species of the acerosa-complex (Voitk et al. 2020(Voitk et al. , 2022. Recently, Voitk et al. (2022) have shown that the species diversity of sphagnophilous Arrhenia is much greater than originally thought and that some are obligate and others facultative sphagnophiles, i.e., A. bigelowii, A. gerardiana, A. telmatiaea, and A. philonotis, respectively. ...
... However, unlike the sphagnophilous and most other mossdwelling Arrhenia, A. bryophthora causes a necrosis on its host and must therefore be considered a true parasite (Voitk et al. 2022). To our knowledge, a similarly destructive lifestyle is only known from the lichenophilic A. peltigerina (Diederich et al. 2022), which is macroscopically similar, but microscopically distinct by the presence of clamp connections and phylogenetically related to species of the auriscalpium/spathulata complex (Voitk et al. 2020). ...
... In the phylogenetic tree based on ITS and LSU sequences (Fig. 1), all specimens of A. bryophthora group in the same moderately supported clade that is the most basal one of all sequences assigned to Arrhenia specimens. Considering the phylogenetic results presented in Fig. 1 and in the literature (Voitk et al. 2020(Voitk et al. , 2022Zhang et al. 2022) and the fact that the current understanding of the genus Arrhenia includes species with facultative and obligate bryophilous, lichenophilous, and saprotrophic lifestyles as well as cyphelloid, pleurotoid, and omphalinoid habitus; it is plausible that this taxonomic group should be revised and studied in more detail in the future. This includes careful morphological and phylogenetic studies based on multi-locus sequencing and comprehensive sampling. ...
Article
Full-text available
The very hot summers of recent years have led to an increase in the number of large forest fires in Europe. We investigated four large fire sites in Brandenburg and Saxony (Germany) up to 4 years after the fires with a focus on studying the post-fire fungal communities. In this context, we documented two species of Agaricomycetes associated with mosses, which are common but particularly emerge on burnt areas, i.e., Arrhenia bryophthora sp. nov. and Bryopistillaria clavarioides sp. nov. The former is an agaric with omphalinoid habit that causes the dieback of the common moss Ceratodon purpureus ; the latter is a clavarioid fungus associated with either Ceratodon purpureus or another common moss, Funaria hygrometrica . Both fungal species appear to be restricted to recently burnt areas and have otherwise not been observed on or in close vicinity of these mosses. Herein, we describe these fungi macro- and micromorphologically as well as on a molecular basis and discuss their taxonomic position and potential lifestyles.
... The genus Arrhenia currently comprises almost 100 species (Index Fungorum, Myco-Bank) and new species are continuously added (e.g., Voitk et al. 2020Voitk et al. , 2022. Lodge et al. (2014) formally established the monophyletic tribe Arrheniae Lücking, comprising the genera Arrhenia, Dictyonema C. Agardh ex Kunth, Cora Fr., and Acantholichen P.M. Jørg. ...
... Initial blast searches in GenBank revealed that the most similar sequences are found in the Arrhenia spathulata group, which corresponds to the second well-supported clade of Voitk et al. (2020). We therefore downloaded sequences of 11 representatives of the A. spathulata group from GenBank to investigate the nrITS variation in relation to the segregation of species and the relations of our samples within this clade ( (Kumar et al. 2018). ...
... . One sequence of A. obscurata (D.A. Reid) Redhead, Lutzoni, Moncalvo and Vilgalys was downloaded and used as the outgroup(Voitk et al. 2020). Calculations of genetic distances (observed p-distance) were done in Geneious and phylo-Table 1. ...
Article
The new species Arrhenia schistidicola Øvstedal & L.Lindblom is described from Western Norway, growing on the moss Schistidium crassipilum on vertical mortar walls. Arrhenia schistidicola is characterized by the lack of a stipe, molecular evidence, and its host moss. It is morphologically similar to A. retiruga, however, molecular analyses show that it is more closely related to A. spathulata.
... In a phylogenetic tree to show the place of Arrhenia acerosa (Fr.) Kühner among some of its relatives within Arrhenia Fr., specimens identified as Arrhenia peltigerina (Peck) Redhead Lutzoni, Moncalvo & Vilgalys seemed to follow three separate supported evolutionary pathways, with collections from the Canadian province of Newfoundland and Labrador (NL) on two of them (Voitk et al. 2020b). That chance observation spurred this study, with the aim to identify the species to which Peck's epithet applies, determines whether the name hides a complex of cryptic species, and learn which are native to NL. Peltigerous omphalinoids have been described in three genera in the past. ...
... Sequences of the internal transcribed spacers of ribosomal deoxyribonucleic acid (ITS rDNA) from selected basidiomata of the target fungus and related species were generated following previously published methods (Voitk et al. 2020a). Outgroup taxa were chosen based on the phylogenetic analyses by Voitk et al. (2020b), and ranking within the genus Arrhenia followed the same work. Alignments were performed using L-INS-i strategy as implemented in MAFFT v7.520 (Katoh and Standley 2013). ...
Article
Full-text available
Phylogenetic study of Arrhenia peltigerina revealed a complex of seven divergent clades. Type specimens of Agaricus peltigerinus and Omphalina cupulatoides fell into separate clades; the latter was recombined as Arrhenia cupulatoides. Four clades were described as new species: Arr. baltica, Arr. fennoscandica, Arr. mohniensis, and Arr. talpoides; the fifth, with only a single specimen, was left formally undescribed. These cryptic species are uncommon—more so in North America than Scandinavia—and collections are often misidentified. Spore measurements separated Arr. baltica from the others by its narrower spores; average measurements help separate some species a bit better than ranges. So far, Arr. peltigerina was found only in North America, Arr. mohniensis and Arr. talpoides in both Europe and North America, and the remainder only in Europe. The host species of Peltigera was Peltigera hymenina for Arr. cupulatoides, Peltigera rufescens for Arr. baltica, and varied for the others. All but one collection came from soil over calcareous bedrock. Small sample size does not permit assigning high confidence to noted interspecific differences; these await confirmation by greater experience from future study.
... last accessed March 2022) lists 83 taxa, 78 species, and 5 varieties, with worldwide distribution; most species have been described from temperate regions. The genus is believed to have a mutualistic relationship with bryophytes, although several members of the A. acerosa complex were noted to have a saprobic relationship with dead plant matter (Voitk et al., 2020). Arrhenia was placed in Hygrophoraceae by Lodge et al. (2013), but an encompassing phylogenetic analysis of the genus has not been done. ...
... The pileus of most species of Arrhenia is greyish, blackish, bluish or brown-grey (Redhead et al., 2002), and can be clearly distinguished from A. nivea. Although there are some near-white species of Arrhenia, e.g., A. eburnea , and some whitish members of the Arrhenia acerosa complex (Voitk et al., 2020) their well-developed gills, and often at least a rudimentary stipe, prevent them from being mistaken for A. nivea. Of white cyphelloid species from (Uzun et al., 2018). ...
Article
Voitk A. & Saar I. (2024) Three sphagnicolous species of Arrhenia: one old, one new, one recombined.-Sydowia 77: 271-290. A cystidiate sphagnicolous Arrhenia, collected in Labrador, led to review of the protologue of Agaricus umbratilis, which described Ag. umbratilis as a black omphalinoid species from wetlands of barrens, characteristic sites for Sphagnum. This species concept matched the black sphagnicolous Arrhenia telmatiaea and its synonym, Arrhenia fusconigra, with no other known look-alikes. These names were synonymized, giving the earliest and sanctioned name, Ag. umbratilis, priority. Two cystidiate collections of Ag. umbratilis, phylogenetically indistinguishable from the acystidiate populations, were discovered; the cystidiate population was described as a new forma of the species, Arrhenia umbratilis f. cystidiata. The original cystidiate sphagnicolous species of Arrhenia that triggered the review of Ag. umbratilis was a distinct species not matching any other species of Arrhenia, and was described as a new species, Arr. burzynskii. Another sphagnicolous omphalinoid, found on the same collecting trips, matched Peck's type for Agaricus montanus, and was recombined as Arrhenia montana.
Article
Full-text available
Protologue of Amanita corylophila, published in Crous et al., 2024. Fungal Planet description sheets: 1614–1696. Fungal Systematics and Evolution 13: 183-440.
Article
Full-text available
Novel species of fungi described in this study include those from various countries as follows: Australia, Aschersonia mackerrasiae on whitefly, Cladosporium corticola on bark of Melaleuca quinquenervia, Penicillium nudgee from soil under Melaleuca quinquenervia, Pseudocercospora blackwoodiae on leaf spot of Persoonia falcata, and Pseudocercospora dalyelliae on leaf spot of Senna alata. Bolivia, Aspicilia lutzoniana on fully submersed siliceous schist in high-mountain streams, and Niesslia parviseta on the lower part and apothecial discs of Erioderma barbellatum onatwig. Brazil, Cyathus bonsai on decaying wood, Geastrum albofibrosum from moist soil with leaf litter, Laetiporus pratigiensis on a trunk of a living unknown hardwood tree species, and Scytalidium synnematicum on dead twigs of unidentified plant. Bulgaria, Amanita abscondita on sandy soil in a plantation of Quercus suber. Canada, Penicillium acericola on dead bark of Acer saccharum, and Penicillium corticola on dead bark of Acer saccharum. China, Colletotrichum qingyuanense on fruit lesion of Capsicum annuum. Denmark, Helminthosphaeria leptospora on corticioid Neohypochnicium cremicolor. Ecuador (Galapagos), Phaeosphaeria scalesiae on Scalesia sp. Finland, Inocybe jacobssonii on calcareouss oils in dry forests and park habitats. France, Cortinarius rufomyrrheus on sandy soil under Pinus pinaster, and Periconia neominutissima on leaves of Poaceae. India, Coprinopsis fragilis on decaying bark of logs, Filoboletus keralensis on unidentified woody substrate, Penicillium sankaranii from soil, Physisporinus tamilnaduensis on the trunk of Azadirachta indica, and Poronia nagaraholensis on elephant dung. Iran, Neosetophoma fic on infected leaves of Ficus elastica. Israel, Cnidariophoma eilatica (incl. Cnidariophoma gen. nov.) from Stylophora pistillata. Italy, Lyophyllum obscurum on acidic soil. Namibia, Aureobasidium faidherbiae on dead leaf of Faidherbia albida, and Aureobasidium welwitschiae on dead leaves of Welwitschia mirabilis. Netherlands, Gaeumannomycella caricigena on dead culms of Carex elongata, Houtenomyces caricicola (incl. Houtenomyces gen. nov.) on culms of Carex disticha, Neodacampia ulmea (incl. Neodacampia gen. nov.) on branch of Ulmus laevis, Niesslia phragmiticola on dead standing culms of Phragmites australis, Pseudopyricularia caricicola on culms of Carex disticha, and Rhodoveronaea nieuwwulvenica on dead bamboo sticks. Norway, Arrhenia similis half-buried and moss-covered pieces of rotting wood in grass-grownpath. Pakistan, Mallocybe ahmadii on soil. Poland, Beskidomyces laricis (incl. Beskidomyces gen. nov.) from resin of Larix decidua ssp. polonica, Lapidomyces epipinicola from sooty mould community on Pinus nigra, and Leptographium granulatum from a gallery of Dendroctonus micans on Picea abies. Portugal, Geoglossum azoricum on mossy areas of laurel forest areas planted with Cryptomeria japonica, and Lunasporangiospora lusitanica from a biofilm covering a bio deteriorated limestone wall. Qatar, Alternaria halotolerans from hypersaline sea water, and Alternaria qatarensis from water sample collected from hypersaline lagoon. South Africa, Alfaria thamnochorti on culm of Thamnochortus fraternus, Knufia aloeicola on Aloe gariepensis, Muriseptatomyces restionacearum (incl.Muriseptatomyces gen. nov.) on culms of Restionaceae, Neocladosporium arctotis on nest of cases of bagworm moths(Lepidoptera, Psychidae) on Arctotis auriculata, Neodevriesia scadoxi on leaves of Scadoxus puniceus, Paraloratospora schoenoplecti on stems of Schoenoplectus lacustris, Tulasnella epidendrea from the roots of Epidendrum × obrienianum, and Xenoidriella cinnamomi (incl. Xenoidriella gen. nov.) on leaf of Cinnamomum camphora. South Korea, Lemonniera fraxinea on decaying leaves of Fraxinus sp. frompond. Spain, Atheniella lauri on the bark of fallen trees of Laurus nobilis, Halocryptovalsa endophytica from surface-sterilised, asymptomatic roots of Salicornia patula, Inocybe amygdaliolens on soil in mixed forest, Inocybe pityusarum on calcareous soil in mixed forest, Inocybe roseobulbipes on acidic soils, Neonectria borealis from roots of Vitis berlandieri × Vitis rupestris, Sympoventuria eucalyptorum on leaves of Eucalyptus sp., and Tuber conchae fromsoil. Sweden, Inocybe bidumensis on calcareous soil. Thailand, Cordyceps sandindaengensis on Lepidoptera pupa, buried in soil, Ophiocordyceps kuchinaraiensis on Coleoptera larva, buried in soil, and Samsoniella winandae on Lepidoptera pupa, buriedinsoil. Taiwan region (China), Neophaeosphaeria livistonae on dead leaf of Livistona rotundifolia. Türkiye, Melanogaster anatolicus on clay loamy soils. UK, Basingstokeomyces allii (incl. Basingstokeomyces gen. nov.) on leaves of Allium schoenoprasum. Ukraine, Xenosphaeropsis corni on recently dead stem of Cornus alba. USA, Nothotrichosporon aquaticum (incl. Nothotrichosporon gen. nov.) from water, and Periconia philadelphiana from swab of coil surface. Morphological and culture characteristics for these new taxa are supported by DNA barcodes.
Article
Full-text available
Hygrophorus roseodiscoideus Bon & Chevassut is a poorly known species so far reported from Mediterranean Quercus ecosystems of western Europe. The lack of reference sequences for this species hampers its reliable identification by mycologists and fungal ecologists in the DNA era. We here fix this issue by epitypifying H. roseodiscoideus with a sequenced collection from the Aix-en-Provence area, where the species has been described from. We also report several sequenced collections from central European countries and Lebanon, that considerably extend the species’ biogeographical distribution. Based on our findings, H. roseodiscoideus can be characterized as a morphologically distinct thermophilous species, associated with oaks on calcareous soils, distributed along the northern coasts of the Mediterranean, from Spain to the Levant, but also colonizing the warmest Quercus woodlands of central Europe.
Article
Full-text available
Molecular studies of sphagnicolous arrhenias in Newfoundland and Labrador (NL) revealed four clades in Arrhenia , three obligate (two scaly capped and one smooth-capped) and one facultative (smooth-capped) sphagnophiles. Critical nomenclatural review of 16 names used for omphalinoid sphagnicolous taxa in the past left five suitable to apply to this group. One scaly capped obligate sphagnophilic clade contained the type for Arr. gerardiana and the other, the type for Clitocybe gerardiana var. fusca ; the latter we introduce as the novel species Arr. bigelowii . It differed from the first by longer spores and a darkening reaction in 10% of collections. The smooth-capped third obligate sphagnophilic clade contained the types of Agaricus telmatiaeus and Omphalina fusconigra ; we recombined it as Arr. telmatiaea . This is the darkest species of the group, with a more northern distribution in NL. The facultative sphagnophile was identified as Arr. philonotis , a lighter smooth-capped species also with a more northern distribution in NL. Unexpectedly, we also collected an unidentified smooth-capped facultatively sphagnophilic species of Omphalina of the O. pyxidata complex. All five species are distributed in both Europe and North America. We describe each species of Arrhenia with a sequenced type, providing new type material where needed. Overall, this study adds new sequences from over 80 specimens of sphagnicolous arrhenias to the two existing in GenBank when we began in 2006, 11 new sequences of the unidentified species of Omphalina , and several other arrhenias.
Article
Full-text available
New Austrian finds of the critically endangered Sarcodon fennicus are presented and illustrated. The determination was confirmed morphologically as well as genetically. Sarcodon fennicus differs from the recently described, very similar Mediterranean species S. amygdaliolens by slightly smaller spores and the habitat in montane coniferous forest. Österreichische Neufunde des vom Aussterben bedrohten Sarcodon fennicus werden vorgestellt und illustriert. Die Bestimmung wurde sowohl morphologisch als auch genetisch bestätigt. Von der kürzlich neu beschriebenen, sehr ähnlichen mediterranen Art S. amygdaliolens unterscheidet sich S. fennicus durch etwas kleinere Sporen und das Habitat im montanen Nadelwald.
Article
Full-text available
Arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) are two fungal groups that colonize plant roots and can benefit plant growth, but little is known about their landscape distributions. We performed sequencing and microscopy on a variety of plants across a high-elevation landscape featuring plant density, snowpack, and nutrient gradients. Percent colonization by both AMF and DSE varied significantly among plant species, and DSE colonized forbs and grasses more than sedges. AMF were more abundant in roots at lower elevation areas with lower snowpack and lower phosphorus and nitrogen content, suggesting increased hyphal recruitment by plants to aid in nutrient uptake. DSE colonization was highest in areas with less snowpack and higher inorganic nitrogen levels, suggesting an important role for these fungi in mineralizing organic nitrogen. Both of these groups of fungi are likely to be important for plant fitness and establishment in areas limited by phosphorus and nitrogen.
Article
Full-text available
UNITE (https://unite.ut.ee/) is a web-based database and sequence management environment for the molecular identification of fungi. It targets the formal fungal barcode-the nuclear ribosomal internal transcribed spacer (ITS) region-and offers all ∼1 000 000 public fungal ITS sequences for reference. These are clustered into ∼459 000 species hypotheses and assigned digital object identifiers (DOIs) to promote unambiguous reference across studies. In-house and web-based third-party sequence curation and annotation have resulted in more than 275 000 improvements to the data over the past 15 years. UNITE serves as a data provider for a range of metabarcoding software pipelines and regularly exchanges data with all major fungal sequence databases and other community resources. Recent improvements include redesigned handling of unclassifiable species hypotheses, integration with the taxonomic backbone of the Global Biodiversity Information Facility, and support for an unlimited number of parallel taxonomic classification systems.
Article
Full-text available
Geographic, morphological and ITS-based molecular review of collections identified as Polyozellus multiplex revealed that it is a complex of five phylogenetic species. Average spore size—either less or more than 7 × 6 µm—splits the complex into a small-spored group of two (P. multiplex and P. atrolazulinus) and a large-spored group of three (P. mariae, P. marymargaretae, and P. purpureoniger). Basidiocarps of the small-spored species are somewhat smaller than the large-spored ones, are various shades of blue, dark all the way to black, with brownish tomentum only in early growth, have dark context, and pilei that tend to flare out at the edge. The large-spored species produce somewhat larger sporocarps, have light or lighter context than the pileipelis, usually retain some brown on the mature pileipellis, the edge of which tends to curl like a cabbage leaf. All will darken or blacken with age. The species of the P. multiplex complex are distributed in the northern coniferous region, with the exception of Europe. One species (P. atrolazulinus) is known from three regions, eastern Asia, western North America and northeastern North America. Two species are known from two regions: P. purpureoniger in eastern Asia and northwestern North America, and P. multiplex in eastern Asia and eastern North America. Two species have been documented in one region only: P. mariae in northeastern North America and P. marymargaretae in western North America. A combination of location, macromorphology and spore size will usually differentiate the species of the complex.
Article
Full-text available
Three species of golden chanterelles were found in Newfoundland and Labrador and were compared with other Cantharellus species by macromorphology, microscopy, and multilocus phylogenetic studies. The commonest species is a member of the C.cibarius group, usually found with Picea, and is differentiated from European C.cibarius by its pinkish-orange rather than yellow hymenium, and from both C.cibarius and C.roseocanus of the Pacific Northwest by its ITS and TEF1 sequences. We describe it as a new species, Cantharellus enelensis; published sequences extend its range to Michigan and Illinois. An uncommon species with reduced, merulioid hymenophore, found growing only with Betula, has rDNA and TEF1 sequences nearly identical to C.amethysteus, but only occasionally shows the amethyst scales on its cap characterizing that species in Europe. Ours is the first report of this species from North America. A third species was recognized by its sequences as C.camphoratus, but our collections, found with Abies balsamea, lack the odour of camphor for which this species was named and have longer and more slender spores than in the original description. This species has not been reported since its description from a single collection in Nova Scotia. All three species are edible.
Article
Molecular studies have shown the type collection of Omphalina oreades to be conspecific with a small brown basidiolichen from the Appalachian range in Newfoundland, both with 4-spored basidia. Two sequences deposited in GenBank, originally identified as O. grisella , fell in the same clade. Sequences of the type collection of Omphalia grisella , with 2-spored basidia, formed a sister clade together with two GenBank deposits, one identified as O. grisella and the other as Omphalina velutina . Omphalina oreades is recombined here as Lichenomphalia oreades comb. nov., and the species redescribed and illustrated. Sequences of the internal transcribed spacer regions of nuclear ribosomal DNA (ITS rDNA) from the algae associated with two collections of L. oreades fell within a highly supported clade with members of an undetermined species of Coccomyxa . The most abundant algal ribosomal large subunit sequence from granules at the base of a different collection matched GenBank sequences identified as Chloroidium ellipsoideum , which is probably either a free-living algal species or a partner to a species of Trapeliopsis. The second most abundant sequence matched Coccomyxa subellipsoidea and is the most likely photobiont of L. oreades . Further studies are required to elucidate the relationship of L. velutina to these taxa.