Circumscription and typification of sphagnicolous omphalinoid species of Arrhenia (Hygrophoraceae) in Newfoundland and Labrador: three obligate and one facultative species

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.


Introduction
Arrhenia was erected as a genus by Fries (1849), and belongs to the Hygrophoraceae (Lodge et al. 2014). As circumscribed by Redhead et al. (2002), it contains species with basidiomata varying from pleurotelloid to omphalinoid, pilei varying from nutant to infundibuliform, hymenia varying from reduced (flat, wavy, wrinkled or folded) to gilled, and stipes varying from absent, reduced, or rudimentary, to fully developed, placed laterally, eccentrically, or centrally, all particularly well represented in arctoalpine habitats. Agaric species with small basiomata having an umbilicate pileus, decurrent gills and central stipe have been described as omphalinoid, although many are not in the genus Omphalina, including many arrhenias. MycoBank (mycobank. org, accessioned 18 Mar 2022) lists over 80 valid species names, a number that is bound to change with more study, as some may become synonymized, while others may turn out to hide complexes of similar taxa. Common traits for most members of the genus include small size, brown-grey colour, preference for open areas, and bryophilia.
In this study we consider only taxa found with Sphagnum L., and use the term obligate sphagnophile for those not found separately from Sphagnum, and facultative sphagnophile for those found in Sphagnum with some regularity, but also among other mosses, usually in barren locations where Sphagnum is present. Our definition excludes species normally preferring other habitats, even if found on occasion in Sphagnum, presumably by chance (e.g. an occasional Craterellus Pers., or a lignicolous species on wood that happens to be in Sphagnum). Our interest to learn more about this group in the Canadian province of Newfoundland and Labrador (NL) was stimulated in part because over 15 years one of these species has been the logo for Foray Newfoundland and Labrador (FNL), the mushroom club of the province, with which three of the four authors are or have been associated.

History of nomenclatural usage
Earlier treatments of species we now consider omphalinoid sphagnicolous arrhenias applied epithets inconsistently, using several names for what seems like a small number of taxa. Increasing consistency in both morphologic species concepts and nomenclature began to emerge during the last 75 years. Eleven major publications by 12 authors who have collected and studied these species (i.e. excluding check lists and general reviews or descriptions of regional mycota), use eight names between them to describe three to four different morphospecies: Favre (1948)-3; Redhead (1979)-2;Clémençon (1982)-4;Lange and Lange (1982)-2;Bigelow (1958Bigelow ( , 1985Kuyper (1995)-3;Breitenbach and Kränzlin (1991)-2;Bon (1997)-4;Gminder (2001)-1;and Elborne (2012)-3. Undoubtedly Jules Favre, father of alpine mycology and mycoecology (Brunner et al. 2017), provided the pivot point to a more coherent and unified taxonomy and nomenclature of sphagnicolous arrhenias. Regular collecting in montane bogs (Favre 1948) gave him unsurpassed familiarity with these species in their environment. Seven seasons of daily collecting trips to the alpine zone of the Swiss National Park (Favre 1955) widened his command of the omphalinoid group of exposed heathland, making his work the cynosure for this mycota, inspiring and influencing subsequent investigators for a long time. With the obvious expertise of his factual observations came occasional nomenclatural conventions based on less accurate influences. These in no way lessened the enormous contribution of Favre, but did propagate some nomenclatural problems in this small group. Below we review names used for omphalinoid sphagnicolous arrhenias by year of publication, taken from the above ten major publications or their authors, as well as names, synonyms, and citations found in the pertinent protologuesadding a few from diverse sources-and assess the suitability of each to sphagnicolous arrhenias.
Review of nomenclature 1. 1782. Agaricus tigrinus Bull., nom. sanct. Described as a white, lignicolous species (Buillard 1782) and later recombined by Fries (1818) as Lentinus tigrinus (Bull.) Fr., nom. sanct., the name by which we know it today. This white wood dweller does not fit a grey-brown, sphagnicolous Arrhenia, and was not considered a sphagnicolous Arrhenia by author or sanctioner. It is listed here because taxonomic confusion has caused some of its homo-and synonyms to be so considered. 2. 1794. Agaricus epichysium Pers., nom. sanct. Described as growing on hollow willow trunks (Persoon 1794), this species is currently known as the wood-dwelling Arrhenia epichysium (Pers.) Redhead, Lutzoni, Moncalvo & Vilgalys. Because rotten wood can also be found in bogs, lignicolous fungi have been collected from Sphagnum (Bunyard et al. 2008). Possibly because of such chance association the name "epichysium" has been applied to some of these species on occasion, persisting as late as 1982 (Lange and Lange 1982). Currently Arr. epichysium is not considered a sphagnicolous species and we do not consider the name suitable for sphagnicolous arrhenias. 3. 1801. Agaricus epichysium var. icmadophilus Pers., nom.
sanct. In translation, Persoon's (1801) entire description, omitting measurements, reads: "very delicate, pileus funnel-shaped and dark grey, gills plano-decurrent and grey. Arising in turf among Sphagnum." Initially Bigelow (1958) preferred this laconian description, sanctioned by Fries (1821), over the use of the light-coloured "oniscus" for the dark sphagnicolous Arrhenia species, and transferred it to Clitocybe, raising it to species level. Later Bigelow (1985) gave up icmadophilus in favour of oniscus, because he felt that the description of Ag. epichysium var. icmadophilus lacked specific identifying features, and "is very short and could also be of several species". In his doctoral thesis, Redhead (1979) followed Bigelow, but states (personal communication, 2018) that by 2002 he had "acquiesced to standard usage". Apart from these brief but transient uses, the epithet has never been in common usage and has not been applied to this group. We find nothing convincing in the scant protologue of A. epichysium var. icmadophilus that compels us to apply the name to any species of sphagnicolous Arrhenia with conviction, and in view of the absence of type material, paucity of detail in the protologue, and lack of continued usage, we are content to follow Bigelow and Redhead in this matter. 4. 1805. "Agaricus tigrinus Alb. & Schw." Fries (1818,1821) cites these authors' publication while describing Agaricus affricatus Fr. This may have confused some workers into thinking the description of Ag. tigrinus by von Albertini and von Schweinitz (1805) is the protologue for a new species, something claimed by neither Fries nor von Albertini & von Schweinitz. The latters' Conspectus is a treatment of regional mycota, made up of both new and previously known species. They mark all new species "nobis" (Latin for "from or by us", in the sense of described as new by us) and provide a list of the new species they describe (Catalogus fungorum novorum nostratium, p XIII). Agaricus tigrinus is not marked "nobis" and does not appear in the list, making it clear that von Albertini & von Schweinitz did not introduce it as a new species. The title of their book states "e metodo Persooniana" to indicate that they refer to Persoon's work. Thus, in this case, they refer to Persoon's 1801 description of Agaricus tigrinus. In turn, Persoon also did not proffer his description as that of a new species, but cites earlier descriptions by Sowerby and by Bulliard. With the latter citation we have come full circle to the first taxon in this list, indicating why it needed to be included. "Agaricus tigrinus Alb. & Schw." does not exist and cannot be used. 5. 1818. Agaricus affricatus Fr., nom. sanct. This epithet is occasionally (mis)applied to sphagnicolous arrhenias, probably because Fries (1818) described it as common in swamps (copiose in paludibus). No doubt the description of an omphalinoid agaric in swamps, with darkening (nigricantibus), grey, bristly scales (squamulis pilosis cineris), may suggest a similarity to scaly capped arrhenias, but Fries clearly described Ag. affricatus as a white-capped mushroom, "albidus" in the protologue (Fries 1818) and "albido" in his sanctioning Systema (Fries 1821  (lurido), light grey (subcinereus), and sparsely wooly (leviter tomentosus). Qualifiers in formal descriptions are used to distinguish the character qualified from its "normal" state; of the two, the qualifier becomes the more important descriptor. If Lasch felt it necessary to add "leviter", it was to stress the sparse nature of the cap ornamentation, to distinguish it from species with truly tomentose caps. Even should one consider "leviter" a relative concept, and dismiss "lightly, slightly, sparsely" or "minutely" as subjective, there should be no misunderstanding the meaning of "tomentosus". The term is specifically used to indicate woolly, fuzzy, fine hair, and not scales; the latter would require terms like "scabrosus" or "squamosus". Lasch's description of Ag. philonotis is compatible with smoothcapped sphagnicolous arrhenias. 9. 1836. Agaricus sphagnicola Berk. The use of this name for sphagnicolous arrhenias has been very confusing. Because Berkeley (1836) described the cap of Ag. sphagnicola as "minutely squamulose", many workers have applied the epithet to scaly capped sphagnicolous arrhenias, while others, like Redhead (1979) in his original report, and Kuyper (1995) found that Berkeley's description, according to Kuyper, "seems to fit better for Phytoconis ericetorum" (= L. umbellifera). A recent detailed analysis of Berkeley's protologue (Voitk 2022) supported the early opinion of Redhead (1979), and agreed with Kuyper (1995) that Berkeley's protologue fit with L. umbellifera, but produced significant conflicts, if applied to sphagnicolous arrhenias. For nomenclatural stability, the species was neotypified with a specimen collected and identified by Berkeley as Ag. sphagnicola, and subsequently identified by Redhead (1979) (Stafleu and Cowan 1976). In addition to illustrating the taxon, Massee's watercolour contained separate analytic figures (figures in addition to those illustrating the species generally, demonstrating details to aid identification), e.g. depictions of spores, gill shape, tiers of lamellulae, stem context and content, etc. The "Handbook of British Fungi, Second and revised edition" (Cooke 1883(Cooke -1891, for which the Illustrations were meant to be an atlas, also appeared in parts; the segment treating Ag. telmatiaeus appeared Jan-Apr, 1885 (Stafleu and Cowan 1976 (1985) states that he first described this entity as Clitocybe sphagnorum Bigelow, "nom. prov.", in his PhD dissertation. However, when he came to describe it formally he decided it was more aptly ranked as a variety, and named it Clitocybe gerardiana var. fusca Bigelow (Bigelow 1958). He described it as a scaly capped sphagnicolous species with dark caps, squamulose in the middle and smooth at the periphery. After publication of the variety, he became misled to believe that it was the same entity as Omphalina fusconigra P.D. Orton, and synonymized his variety with Orton's species (Bigelow 1985). Bigelow's description remains suitable for scaly capped sphagnicolous arrhenias. 16. 1960. Omphalina fusconigra P.D. Orton. Orton (1960) was unable to find an existing "description which fit this rather characteristic sphagnicolous agaric", which differed "from the other sphagnicolous species of Omphalina in consistently darker blackish brown cap and stem…" To Orton the main macroscopic character worthy of note, which readily distinguishes this species from other sphagnicolous arrhenias, is the dark, blackbrown colouring, not cap texture. He described the cap as "sometimes slightly rugulose or scurfy-flocculose at centre", in other words an irregularity that was the exception, minimal, and limited. Both wrinkled (rugulose) and flat surfaces can be scaly, scurfy-flocculose, or smooth. Probably because scaly capped arrhenias are commonly encountered in bogs, the mention of any cap irregularity, no matter how uncommon, limited or inconsequential, tempted misinterpretation of O. fusconigra as a scaly capped taxon. For example, that is probably what led Bigelow (1985) to synonymize his scaly Clitocybe gerardiana var. fusca with Orton's dark but smooth-capped Omphalina fusconigra. We conclude that this name, currently Arrhenia fusconigra (P.D. Orton) P.A. Moreau & Courtec., is suitable to apply to dark smooth-capped sphagnicolous arrhenias.
In summary, from a field of 16 potential candidates, we identified five epithets that fit the species we have observed in our bogs, two with clearly scaly caps (Ag. gerardianus, and C. gerardiana var. fusca) and three with primarily smooth caps, albeit keen observation may reveal some irregularity or fine surface ornamentation at times (Ag. philonotis, Ag. telmatiaeus, and O. fusconigra).

Materials and methods
Type collections Peck (1873) listed two collections in his protologue of Ag. gerardianus, but did not specify either as type; only one of the two syntypes could be located. All four basidiomata (NYSf 1339.1-4) of this collection were examined, but their condition was not sufficiently robust to permit sequencing. Two attempts to find fresh collections around the type locality near Sand Lake, NY, were unsuccessful, so that one of Peck's contemporaneous collections from Essex Co., NY, identified by him as Ag. gerardianus, was selected (NYSd 4725). One basidioma (NYSd 4725.1) from this was used for both DNA extraction and microscopy. The spore size of NYSd 4725.1 matched that of all four basidiomata in Peck's syntype, NYSf 1339.1-4. The type collection for Clitocybe gerardiana var. fusca, collected by A.H. Smith, contains over 30 basidiomata. From that collection, MICH made a gift of a fragment consisting of approximately ½ pileus with gills attached, which was used for both DNA extraction and microscopy. The remaining material from this gift was deposited in TUF (TUF117871). One basidioma from the type collections of Ag. telmatiaeus in NY, and one from O. fusconigra in K were sequenced successfully.
Other collections Study collections were selected from over 150 collections identified to be sphagnicolous omphalinoid arrhenias in the private herbaria of Andrus Voitk and FNL, collected with normal field techniques and air-dried at 20-30°C . Selection attempted to incorporate samples of all potential "species" and to represent a wide distribution in NL. In addition, nine collections from an archipelago near Saint-Augustin, Québec, on the north shore of the St Lawrence Basin, a similar area contiguous with the southern Labrador coast, were included. Specimens not associated with Sphagnum were included if Sphagnum was nearby and collections of similar sphagnicolous specimens had been made. Three collections from mossy grassland with no nearby Sphagnum were added to compare to similar specimens collected in Sphagnum.
Of 64 selected regional collections, sequences were obtained from 60. Two were excluded after analysis because they were unidentified singleton species from a distant portion of the Arrhenia tree for which we had no photo and inadequate habitat or substrate data, leaving 58 sequenced collections, which make up the core regional target material for this study (51 from NL, seven from QC; 36 from Voitk, 22 from FNL). In addition, 35 extraregional collections of sphagnicolous arrhenias from various herbaria were sequenced for this study, to which were added two GenBank sequences of sphagnicolous arrhenias available at the time. Herbaria are designated with Index Herbariorum codes (Thiers 2021). A few additional collections were made, examined, and sequenced after the phylogenetic analysis had been completed; these were not included in the tree, but have been added to the Tables, material deposited as the others.
Macroscopic examination NL specimens were photographed in situ and macroscopic descriptions were based on fresh specimens. Apart from capsule descriptions of types, only personally observed sequence-identified regional specimens were used for taxonomic descriptions.
Microscopic examination Light microscopic observations (Zeiss 392560 with Apo 100/1.25) were conducted at 1000 × magnification (oil immersion), using 2% KOH. Spore length and width were measured to 0.5-μm accuracy; measurements deviating from 0.5-μm increments are due to calculation of an objective correction factor. A minimum of 20 spores per single basidioma was used to calculate average values, and Q (length width ratio) was rounded to one decimal point. Statistical analysis of spore sizes was done with a Student's t-test (two-tail, two-sample assuming equal variances) using the data analysis package in Microsoft Excel 2013.
DNA extraction and nuclear sequencing DNA extraction and nuclear sequencing were done in three laboratories. Extraction at Bridgewater College (sequences marked with * in Table 1) followed Lickey et al. (2003); extraction at The Field Museum (sequences without a UDB code and not marked with * in Table 1) followed Sulzbacher et al. 2016; extraction at Tartu University (UDB code in Table 1) followed Saar and Voitk (2015). Sequences were inspected and assembled using Sequencher 5.4 software (Gene Codes, Ann Arbor, USA), and uploaded into PlutoF cloud database (Abarenkov et al. 2010b), including the collection data, partly reachable through the public web output UNITE (http//unite.ut.ee; Abarenkov et al. 2010a). Nucleotide sequence data were deposited in GenBank (see Tables 1, 2, and 3).
Phylogenetic analysis The alignments were performed using L-INS-i strategy as implemented in MAFFT v7.475 (Katoh and Standley 2013). Minor manual adjustments were performed with SeaView 4.7 (Gouy et al. 2010). Bayesian inference of phylogeny was performed with MrBayes 3.2.6 (Ronquist et al. 2012) with default values; the first 100K generations without reaching a stable likelihood score were discarded.

Results
The specimens studied are summarized in three tables. Table 1 gives details of collections whose sequences make up the phylogenetic tree in Fig. 1, excluding an unidentified species in the Omphalina pyxidata complex and the sphagnicolous arrhenias. Data for collections of the unidentified species in the Omphalina pyxidata complex examined for this study, whether shown in Fig. 1 or not, are summarized in Table 2, and data for the sphagnicolous arrhenias examined for this study, including those used to make up the phylogenetic trees in Figs. 1 and 2, as well as those added later and not in Fig. 1, are shown in Table 3.

Phylogeny
The studied collections produced two singleton collections (Arrhenia spp. 1 and 2) and four clades within Arrhenia, as well as a monophyletic clade that fell in Omphalina, labeled Omphalina sp. (Figs. 1 and 2). Two scaly capped sphagnicolous species arose as sister clades from the most ancestral lineage in the arm leading to Arrhenia, while the two smooth-capped species emerged later. A more detailed look at these four species (Fig. 2) reveals that the epitype of Ag. gerardianus (NYSd 4725) fell into one scaly capped clade, giving it its name, and Bigelow's holotype of C. gerardiana var. fusca fell into the other, which we describe as a new species, Arr. bigelowii. O. fusconigra a later synonym of Ag. telmatiaeus. We transfer the latter to Arrhenia as Arr. telmatiaea (Berk. & Cooke) Voitk & I. Saar, comb. nov. The remaining clade we identify as Arr. philonotis, and declare a neotype from Germany for the species. Two singleton specimens, labeled Arrhenia sp. 1 and Arrhenia sp. 2 on Fig. 1, fell elsewhere within Arrhenia. They were initially identified as "Arrhenia sphagnicola", a name primarily, but not exclusively, used for scaly capped sphagnicolous arrhenias at the time; because we have very little tissue left, lack notes or photographs for these collections, including whether both were sphagnicolous or scaly, and have not collected them again on several return trips to the same sites, we do not treat them here.

Macromorphology
Phylogenetic clades correlated with morphological characters. Arrhenia bigelowii and Arr. gerardiana, both in the earlier diverging lineage, have pilei usually under 20 mm in diameter, covered to various degrees by radially arranged darkening scales with upturned tips (Figs. 3a-c and 4a-e). Macroscopically the upturned scale tips make distinction between scaly and smooth-capped specimens easy in vivo, but the difference is not readily apparent after drying because often the upturned tips are not obvious microscopically even after rehydration. About 10% or less of the variably brownish Arr. bigelowii specimens undergo a marked darkening reaction ( Fig. 4b, d); the species as a whole is a little darker than Table 1 Details of sequenced specimens in order of appearance in Fig. 1, excluding the single NL species in the Omphalina pyxidata complex (shown in Table 2), and the sphagnicolous arrhenias (shown in Table 3      the brown Arr. gerardiana, but lighter specimens are indistinguishable from the latter (Fig. 4a, e). Occasionally the scales disappear from some very mature (caps over 20 mm in diameter) specimens of Arr. gerardiana (Figs. 3d and 4f), possibly through loss of the outer pileipellis layer, making such specimens difficult to distinguish from similar smooth-capped taxa, particularly the Omphalina sp. Arrhenia philonotis and Arr. telmatiaea, the two smooth-capped species (Fig. 5) in the more derived lineage, have mature cap diameters over 20 mm, at times reaching over 35. Fine adpressed hairs outlining similar radially arranged scale shapes with centrifugal points are spread sparsely about the cap of Arr. philonotis, occasionally rising to form scattered thin hairs, better observed with magnification (Fig. 3e). Rudimentary outlines of similar scales can be seen in the pileipellis of Arr. telmatiaea as well (Fig. 3f, g), which remain adpressed without tips rising up. The original descriptions of both Agaricus telmatiaeus and Omphalina fusconigra fit the dark smooth-capped species (Fig. 5c-e). Orton's description of the cap texture was confirmed by our observations: the cap of 17 basidiomata can be observed on photos of eight collections confirmed by molecular studies to be conspecific with O. fusconigra. All caps are smooth, but one rather old basidioma reveals scurfy-flocculose texture limited to the depth of the navel. In other words, this is not a scaly capped species, but just as Orton described, a smooth-capped species, which only on occasion (<6% of basidiomata in our experience) develops wrinkling irregularity in the depth of its navel. The Omphalina sp. (Fig. 5f, g) has the largest basidiomata, occasionally over 35-mm cap diameter, a smooth cap, and a colour that leans more toward reddish than greyish brown. When found in Sphagnum, it can add to the confusion of identifying these species.

Micromorphology
All species have clamp connections through all tissues, primarily 4-spored basidia, and lack cystidia. Basidiospores of Arr. telmatiaea are the smallest, averaging 7.3 × 4.7 μm, separating it from Arr. philonotis, averaging 8.7 × 5.6 μm, most of the time. Basidiospores of the scaly capped species are longer and narrower than the spores of the smooth-capped species, but do not separate well from each other (Fig. 6).  Lutzoni (1997) Those of Arr. gerardiana are smaller than those of its sometimes darkening sister, but the majority cluster in the overlapping section, making measurement a helpful differentiator only at the extremes of their combined range. The pileipellis of all four species consists of repent clamped hyaline cells with a modest to moderately copious amount of incrusted brownish pigment, some evident as small plates on the cell wall ( Fig. 7a-d). Incrustation is most obvious in the scaly capped species and least in the hyaline hyphae of Arr. telmatiaea, where incrustation is subtle and requires time to find. The scales of Arr. bigelowii and Arr. gerardiana resemble each other, fascicles of thick pileipellis hyphae turning to project upwards to form a visible acute tipped scale (Fig.  7e, f), with unpigmented clear rounded terminal cells.

Ecology and distribution
Three species were observed to be obligate sphagnophiles. Of these, the two scaly capped species, Arr. gerardiana and Arr. bigelowii, were sympatric, on occasion found in the same bog at the same time. The dark smooth-capped Arr. telmatiaea was also an obligate sphagnophile. The smooth-capped Arr. philonotis was a facultative sphagnophile, growing in bogs, heaths, moors, and other exposed places, among Sphagnum, but at least equally often with other mosses. The Omphalina sp. was collected from bogs with Sphagnum ( Fig. 5g) or heaths and moors with other mosses, but was far more common in grasslands with low moss (Fig. 5f). All four species of Arrhenia were distributed throughout both Europe and North America (including Greenland). In NL smooth-capped arrhenias were more northerly, found in Labrador, the Great Northern Peninsula, and along the northern east coast, bathed by the Labrador Current. The scaly capped species extended throughout the province. Diagnosis. Basidioma 8-33 mm tall, in Sphagnum; cap usually under 20-mm diameter, brown, umbilicate, radially striate, scaly; gills decurrent, light brown; stem light brown; obligate sphagnopilic denizen of temperate to subarctic raised bogs. Pinnate scales distinguish it from smooth-capped sphagnophilic arrhenias; in addition to being somewhat darker most of the time, it can be separated from the other scaly capped sphagnicolous species, Arr. gerardiana, by an occasional darkening reaction, tendency for more inverted bowl shaped pilei, longer spores, and an ITS sequence difference of 37 basis pairs.
Capsule varietal isotype description. Studied material was approximately one-half of a dried pileus with gills attached, approx. 1.5 cm in diam. Cap striate, umbilicate. Microscopic examination of a squash section of gill revealed elongate elliptical spores 6.1-11.4 × 3.2-4.9 μm (ave. 8.4 × 4.0, Q 1.7-2.5, ave. 2.1, n = 22 spores). No cystidia, but clamp connections readily evident. Four-spored club-shaped basidia, approx. size 34 ×7 μm. Cap structure not examined. Macromorphology ( Fig. 3a; 4a-d): Basidioma: Brown, s t i p i t a t e , a b o u t 8 -3 3 m m t a l l , i n S p h a g n u m . Uncommonly becomes dusky, with various degrees of black and grey adding to or covering the brown colouration. Stimulus for this change not known. Pileus: 4-24-mm diameter, usually deeply umbilicate and often shaped like an inverted bowl, edges becoming more plane, then crenulate with age, translucently striate, covered with somewhat concentric radially arranged scales with darker brown, burr-like, uplifted, centripetally narrowing ends. Radially ribbed with darker narrow brown bands over lamellae and lamellulae, alternating with wider, tan intervening bands; the latter become sulcate with time. Cap margin darkens with time. Lamellae: moderately spaced, smooth edged, deeply decurrent, with usually three intervening, small lamellulae; developing a few low crossveins beyond maturity, forking very rare; light brown, developing darker edge. Stipe: 10-23 × 2-5 mm, cylindric, straight; becoming somewhat hollow; brown; minutely tomentose, glabrescent with age, sparse white tomentum at base. Context: whitish, odour unremarkable.
Habitat: Open raised Sphagnum bogs in groups of 1-6 separate basiomata, attached to living Sphagnum with white mycelial tomentum, associated with various bog plants such as Vaccinium oxycoccos L., V. macrocarpon Aiton, Rubus chamaemorus L., Empetrum nigrum L., Andromeda polifolia L., and various bog orchids, reeds and grasses, June-Sept, most plentiful in July. May be found in the same bog at the same time as Arr. gerardiana.
Distribution: Known from North America and Europe; in NL found throughout the province, more common in Newfoundland than Labrador.
Additional specimens examined: See Table 3. Comments: Often indistinguishable from Arr. gerardiana: darkening reaction often absent and pileus becomes more plane with age. Although statistical analysis shows that the spore size difference is highly significant (for Q, t = −6.31; d.f. = 788; p < 0.001), spore sizes of the two species overlap sufficiently to make this character useful only when the averages occupy the extremes of their respective range. We elected to describe it as a new species because we wished to provide a fully examined and robust type collection for posterity. Bigelow (1958) described the growth pattern as "scattered", typical of scaly capped sphagnicolous arrhenias, whose individual organisms usually produce 1-2 fruiting bodies at any one time, and seldom more than six. Smith's holotype collection of C. gerardiana var. fusca consists of more than 30 basidiomata and must sample several individual organisms. Because both Arr. bigelowii and Arr. gerardiana are macroand micromorphologically very similar, known to occur in the same bog at the same time, a multi-individual collection increases the likelihood of containing both species. We have not examined the entire collection, but only a cap fragment, from which tissue has been removed for both microscopy and molecular studies. This seems inadequate to designate as lectotype, when an abundance of tissue remains in the varietal holotype collection, and typifying the species with an ample and fully examined collection seems the more prudent choice. In addition, given the considerable confusion caused by the name "fusconigra" in the past, avoiding a name from the same root seems advantageous, all the more appropriate because this gives an opportunity to honour Bigelow, the first to recognize this species a new taxon.  Capsule lectotype description. The lectotype collection NYSf 1339.1-4 consists of four dried dark brown basidiomata glued to sheets (.1 and .4 further secured with cloth tape), reasonably intact with pieces of stipe and pileus missing. Tallest approx. 5.5 cm high (stipe base to top of upturned cap edge), with widest cap diam. approx. 1.2 cm. Caps striate, umbilicate to funnel-shaped. Microscopic examination of a squash section of gill (3% KOH) from each of the four basidiomata revealed pip-shaped to elliptical spores 6.8-12.4 × 3.4-5.1 μm (ave. 9.2 × 4.2, ave. Q = 2.2, n = 100 spores). No cystidia. Clamp connections throughout all tissues. Four-spored (rarely two) club-shaped basidia, approx. size 24 × 7 μm. Cap structure not examined.
Capsule epitype description. The epitype collection NYSd 4725, consisted of ten relatively intact dried dark brown basidiomata, most taped or glued to sheets, with parts missing, and additional pieces with most of the basidiomata missing. Tallest approx. 5.5 cm high (stipe base to top of upturned cap edge), with widest cap diam. approx. 1.2 cm. Caps striate, umbilicate to funnel-shaped. The epitype was selected and designated NYSd 4725.1. Microscopic examination of a squash section of gill revealed pip-shaped to elliptical spores 7.9-11.5 × 3.3-4.2 μm (ave. 9.8 × 3.8, ave. Q = 2.6, n = 20 spores). No cystidia. Clamp connections throughout all tissues. Four-spored club-shaped basidia, approx. size 24 × 7 μm. Cap structure not examined. Macromorphology (Fig. 3b-d; Fig. 4e, f): Basidioma: Brown, stipitate, about 10-35 mm tall, in Sphagnum. Pileus: 5-25 mm diameter, usually deeply umbilicate, edges curved down somewhat at the margin, but rarely assuming an inverted bowl shape, becoming plane, then crenulate with age, translucently striate, covered with somewhat concentric radially arranged scales with darker brown, burr-like, uplifted, narrow distal ends. These scales seem to recede with age, and occasional very mature specimens with large caps may have Fig. 2 Best-scoring tree focusing on the four treated sphagnicolous arrhenias, based on maximum likelihood analysis of the ITS barcoding marker. Country (plus province/state for USA and CA) identified by ISO Alpha 2 codes. "Lab" marks NL specimens from Labrador. Types shown in bold yellow. Specimens identified by current names, except types, which are identified by the original epithets. All sequences were generated for this study, except U66449 and U66453, the only deposits in GenBank from this group when we began this investigation. ML bootstrap support ≥70% and the Bayesian posterior probabilities ≥95% are shown above and below the branches (bs/pp), respectively Fig. 3 Cap texture of sphagnicolous arrhenias. Bars = 10 mm. a The dramatically scaly cap of Arr. bigelowii (08.08.12.av05), unlikely to be described by diminutives, "sparsely wooly" or "minutely squamulose". b Peck's aquarelle of his Ag. gerardianus with evident scales (photo courtesy NYS). c The equally obvious scaly cap of Arr. gerardiana (05.07.03.av02). d The smooth cap of a very mature desquamated Arr. gerardiana (17.07.05.av05), making identification difficult. e Cap of Arr. philonotis (KL-015) showing subtle "scale pattern" embedded in the pileipellis, occasionally elevated to create a scattering of very fine hairs. f A brownish and lighter cap of Arr. telmatiaea (GNP-064). A pattern resembling the radial scales of Arr. bigelowii or Arr. gerardiana can be seen, but these remain entirely adpressed in the pileipellis, with no attempts of the tips to rise. g Cap of a very dark Arr. telmatiaea (05.09.08.av02). The adpressed "scale pattern" in the pileipellis is present, although not as evident  (Figs. 3d; 4f). Narrow brown radial bands over lamellae and lamellulae, alternating with wider, tan intervening bands; the latter become minimally sulcate with time. Cap margin darkens with time. Lamellae: moderately spaced, smooth edged, deeply decurrent, usually with three intervening, small lamellulae; developing a few low crossveins beyond maturity, forking very rare; light brown, developing darker edge. Stipe: 10-25 × 2-5 mm, cylindric, straight; becoming somewhat hollow; minutely tomentose, which may disappear with age, brown with sparse white tomentum at base. Context: whitish, odour unremarkable.
Habitat: Open raised Sphagnum bogs in groups of 1-6 separate basidiomata, attached to living Sphagnum with white mycelial tomentum, associated with various bog plants such as Vaccinium oxycoccos, V. macrocarpon, Rubus chamaemorus, Empetrum nigrum, Andromeda polifolia, and various bog orchids, reeds, and grasses, June-September, most plentiful in July. May be found in the same bog at the same time as Arr. bigelowii.
Distribution: Europe and North America; suspect Holarctic distribution. In NL, throughout the province.
Additional specimens examined: See Table 3. Comments: Its cap, scaly throughout, sets it apart from smooth-capped sphagnicolous omphalinoids. This character may be lost in very few overly mature and large specimens, requiring microscopic examination to distinguish them from Arr. philonotis, the Omphalina species, or even lightercoloured Arr. telmatiaea. Differs from Arr. bigelowii by its more plane pilei, by not turning grey to black in response to unknown stimuli, and shorter spores; these characters are not always evident.
Peck (1873) mentioned two collections in his description of Agaricus gerardianus (NYSf 1339 and NYSf 1340), which become syntypes because he did not designate either as holotype. NYSf 1340 is presumed lost; we designated the remaining collection (NYSf 1339.1-4) with its four basiomata, as lectotype for the species. Comparison of spore size has allowed us to conclude that the lectotype is conspecific with collection NYSd 4725, identified by Peck as Ag. gerardianus. Because the lectotype did not yield DNA, but NYSd 4725 did, we designated the latter as epitype for Arrhenia gerardiana, thus defining the clade in which it resides as that species.
Capsule neotype description. The neotype collection KR-0003880 is fragmented with no completely intact basiomata. Larger pieces are parts of at least 4-5 pilei and twice that number of stems, suggesting that the original collection may have consisted of around 8-10 basiomata. Although fragmented, there is a generous amount of material, which otherwise seems to be in good shape. Small strands of moss are seen, including at least one stem attached to what seems to be Sphagnum. By extrapolation, the tallest dried basioma is approx. 5 cm high (stipe base to top of upper cap edge), with widest cap diam. approx. 2.5 cm. Caps smooth, umbilicate. Microscopic examination of a squash section of gill revealed pip-shaped to elliptical spores 7.7-10.4 × 5.2-7.6 μm (ave. 8.9 × 5.8, ave. Q = 1.5, n = 20 spores). No cystidia. Clamp connections throughout all tissues. Four-spored club-shaped basidia, approx. size 24 × 7 μm. Cap structure not examined. Macromorphology ( Fig. 3e; 5a, b): Basidioma: Brown, stipitate, about 10-38 mm tall, in heaths, bogs and moors with Sphagnum or other moss. Pileus: 5-30-mm diameter, umbilicate, edges curved down becoming plane and crenulate with age, translucently striate, smooth, often covered with thin, fibrillose, adpressed, flat scales, whose tips may become slightly uplifted as scattered thin hairs, denser in the umbilicus. Narrow brown radial bands over lamellae and lamellulae, alternating with wider, tan intervening bands; the latter may become sulcate with time, giving the cap a radially ribbed appearance. Cap margin darkens with time. Lamellae: moderately spaced, smooth edged, deeply decurrent, with 3-5 intervening, small lamellulae; may develop a few low crossveins beyond maturity, forking very rare; light brown, developing darker edge. Stipe: 10-25 × 2-5 mm, cylindric, straight; becoming somewhat hollow; minutely tomentose, glabrescent, brown with sparse white tomentum at base. Context: whitish, odour unremarkable.
Distribution: Known from North America and Europe; Holarctic distribution suspected; not as southerly as the scaly capped species, in NL so far known only from Labrador.
Additional specimens examined: See Table 3. Comments: Basiomata resemble those of the scaly capped species, but are readily distinguished by their obviously smooth caps of somewhat greater diameter, and light colour tending more to greyish brown. Distinguished from Arr. telmatiaea by its lighter hue and from the Omphalina species by its greyish rather than reddish brown hues and broader spores.
Habitat: Open raised Sphagnum bogs in groups of 1-6 separate basiomata, attached to living Sphagnum with white mycelial tomentum, associated with various bog plants such as Vaccinium oxycoccos, V. macrocarpon, Rubus chamaemorus, Empetrum nigrum, Andromeda polifolia, reeds and grasses, July-September, most plentiful in August. May be found in the same bog at the same time as other northern species.
Distribution: Known from North America and Europe; suspected Holarctic distribution; in NL not as southern as the scaly capped species, so far known only from Labrador, the Great Northern Peninsula, and the northern east coast.
Specimens examined: See Table 3. Comments: Its obviously and relatively even dark colour distinguishes it from the other smooth-capped sphagnicolous species, Arr. philonotis, but on occasion may be more dark brown than near-black, requiring microscopic examination to confirm identification. Omphaliaster borealis (M. Lange & Skifte) Lamourenot recorded in NL to date-is macroscopically very similar, also occurring in northern or alpine raised Sphagnum bogs, but can be distinguished by its globose, spinulose spores (Vašutová et al. 2013

Discussion
Two characters have been particularly troublesome for nomenclatural consistency in the past. The first is lack of an early name for the common scaly capped sphagnicolous arrhenias, resulting in the application of incompatible epithets like tigrinus and affricatus to this group, or overinterpreting descriptions of cap vestiture in an effort to shoehorn the description to fit "scaly", e.g. interpreting Lasch's "leviter tomentosus" for Ag. philonotis as scaly instead of sparsely hairy, taking an occasional wrinkled umbilicus of O. fusconigra to mean a consistently scaly cap, or equating Berkeley's description of minute cap surface irregularity of Ag. sphagnicola with the rough scaliness of sphagnicolous arrhenias. The second confusing character is dark hue. Fries contributed to this by synonymizing his Ag. oniscus with a light species in his protologue (Fries 1818) and sanctioning work (Fries 1821), but later (Fries 1867) applying the name to a different and dark species, causing the name to be applied to dark arrhenias (Voitk 2022). Variability of the truly dark species, Arr. telmatiaea, from opaque near-black (Fig 3g; 5b) to translucently striate dark brown (Fig. 5c, d), lightening even to tan on drying, increases the opportunity to confuse it with darker specimens of Arr. philonotis (Fig. 5b), desquamated older Arr. gerardiana ( Fig. 3d; 4f), or the unexpected Omphalina species. In addition, the ill-understood darkening reaction, sometimes extreme (Fig 4b, d), of Arr. bigelowii adds further confusion to these two taxa.
Spore size is genetically determined, and functioned as an indicator of genetic lineage before the DNA era. Our four clades separated into three groupings by spore size (Fig. 6,  Fig. 8a): one for each of the two smooth-capped species and one larger grouping for the two scaly capped ones, whose constituent members proved difficult to separate from each other due to a large area of overlap in spore size (as well as similar macroscopic appearance). Favre (1948), treating Omphalia sphagnicola (Berk.) P. Karst. as a scaly capped species, stressed the wide variability of size and shape of its spores (7.5-15 × 3-6 μm; average 11-4.3), the ranges indicating that he must have included both Arr. gerardii and Arr. bigelowii under the name. A decade later Bigelow (1958) described the species with bigger spores as a separate taxon, but this was not adopted, even by him, and it took molecular studies to confirm his observation.
To get an idea of the consistency of name use by the major pre-DNA workers cited in the "Introduction", we plotted the spore size ranges for our four species (Fig. 8a), and then superimposed the spore measurements reported for each name by the same leading workers (Fig. 8). Full ranges, including extremes, were used for each, save for Lange and Lange (1982), who reported only the range of average values. The overall pattern was reasonably similar to ours: a cluster around each of the two smooth-capped species, and one covering both scaly capped ones (Fig. 8b), which suggests that the same four species were studied. Figure 8c-j shows spore sizes reported for each name used, distributing the eight names among half that number of species. The epithets most often applied to this group by the selected authors were oniscus and philonotis, both used in eight studies. Interestingly, spore measurements of seven of the eight species to which oniscus was applied (Fig. 8d), fit with those of Arr. telmatiaea; the measurements reported by Kuyper (1995) seem to fit better with Arr. philinotis while his measurements for the epithet philonotis seem to fit better with our telmatiaea. The relatively good fit of spore measurements to one epithet may tempt one to consider conserving oniscus over telmatiaea, until one notes that epithets other than oniscus have also been applied to species with spores matching those of Arr. telmatiaea: fusconigra (Bon 1997, Clémençon 1982but not Bigelow 1985), icmadophila (Bigelow 1958;Redhead 1979), epichysium (Lange and Lange 1982), and philonotis (Kuyper 1995;Lange and Lange 1982).
What consistent species concept may have been indicated by spore size loses most of its validity once other characters are considered. For example, our observations suggest that Arr. telmatiaea is an obligatory sphagnophile, fitting the illustration of the type by Massee depicting basidiomata intimately attached to Sphagnum, and the several descriptions of Messrs Berkeley, Broome and Cooke, all stating that it occurs "in Sphagnum". Of the eight studies applying oniscus to a species whose spore measurements fit those of Arr. telmatiaea, only one (Gminder 2001) described it as an obligatory sphagnophile. Five (Favre 1948;Clémençon 1982;Bigelow 1985;Breitenbach and Kränzlin 1991;Elborne 2012) described it as a facultative sphagnophile, and two (Kuyper 1995;Bon 1997) stated that it grew with other mosses, but not with Sphagnum. Thus, some species other than Arr. telmatiaea must have also been considered part of the taxon to which oniscus had been applied. The most likely candidate is Arr. philonotis, which shares its darker colour, smooth cap, liking for moorland in cold climates, and a significant overlap of spore size, but not the obligatory relationship to Sphagnum. Thus, although the epithet oniscus has enjoyed constant use in the past, constant is not consistent. Even among experts its use has been applied to several species, to all of which other names have also been applied. Conserving a name for only a fragment of its application, when better names with sequenced types are available, lacks appeal; any credibility such conservation may have had is lost, when it creates major conflict with the protologue. Therefore, we elected to apply Ag. telmatiaeus, the earliest available name, to this taxon, the sequenced type of which (along with the sequenced type of O. fusconigra) nestles in this clade. Agaricus telmatiaeus has been left largely unused in the past, partly because of initial confusion around the name, and lack of a type specimen in Kew (Dennis 1948), all of which relegated it to a nomen dubium (Legon and Henrici 2005). Bigelow (1985) examined its type in NY, and recorded spore measurements that fit O. fusconigra. He stated these taxa should be compared, but because he was unable to confirm incrusted pigmentation, was uncertain about its correct placement. Examination of our own collections confirms that the species has incrusted pigment in its cap hyphae (Fig. 7d).
Because it seemed to have the best potential for consistent application, we examined the epithet oniscus in detail. Similar inconsistency was observed with the three other species. Epithets with spore measurements fitting best with Arr. philonotis were philonotis (Favre 1948;Clémençon 1982;Bon 1997;Elborne 2008) and umbratilis (Lange and Lange 1982). Bon described the species as an obligatory sphagnophile, suggesting he had another species in mind. Epithets with spore measurements fitting best with the two scaly capped species were gerardiana (Bigelow 1958;Redhead 1979;Kuyper 1995;Elborne 2008), sphagnicola (Favre 1948;Clémençon 1982;Breitelbach & Kränzlin 1991;Bon 1997), and fusca (Bigelow 1958). In other words, past nomenclature has been inconsistent even in the hands of Fig. 8 Comparison of spore measurements of our four species, with those reported in the ten major publications cited in the "Introduction". a Measurement as for Fig. 6. Ranges for our four species. b. Combined ranges of all species reported by all cited authors, represented by translucent white ovals superimposed on our results. c-j Ranges for each epithet used by the cited authors on each separate view, again superimposed on our measurements. The ranges recorded by Lange and Lange (1982) use average values of the collections, not the complete range leading workers, by using multiple names for one species, by applying the same name to different species, and seemingly including more than one of the currently identified species under one name. Any nomenclatural reconciliation in this setting will result in instability to this small group of taxa. We identified Arr. philonotis as a facultative sphagnophile. Whether it interacts with Sphagnum at all or merely shares with it a like for similar habitats is a matter for investigation. Lücking (personal communication) states that philonotis is the commonest epithet applied to sphagnicolous arrhenias in European herbaria, which is disproportional to its prevalence among the four taxa, suggesting that unless A. philonotis is much commoner in Europe than NL, the name has been applied to more than one species. Our review suggests the latter. Molecular studies enabled us to name all other clades, leaving Arr. philonotis for the last. However, the application of the name was not by default: the light grey colour and scattered fine pileal hairs (Fig. 3e) described in the protologue enabled us to match this name to only one species. The type for Ag. philonotis, presumed lost, came from a bog close to Berlin, near the North Sea. We selected the closest collection with good material that we sequenced as epitype. It came from a bog near Baden-Württemberg, Germany, a more midcontinental location in the foothills of the Alps, about 500 m asl., a slightly different biome than that of the type location, but we were reassured by finding some of our sequenced specimens in coastal barrens and moors similar to Lasch's collecting region. This decision seems to be supported by at least three major workers (Favre 1948;Kuyper 1995;Elborne 2008), who apply this epithet to collections with spore measurements similar to ours. That said, of the four, we know Arr. philonotis the least, and have only seen four collections of it in its habitat. Therefore, our descriptions (based only on sequenced specimens directly observed by us) should benefit from augmentation by future observations. Nomenclatural uncertainty spreads from leading workers to all writings in both professional and amateur journals and books. For example, in his pursuit of the genus Galerina in Auvergne, René-Jacques Bouteville (1998) spent a lot of time in bogs, which resulted in a very nice and compact review of sphagnicolous omphalinas. Much as we, he came up with four species, Omphalina sphagnicola (Berk.) M.M. Moser, O. philonotis (Lasch) Quél., O. oniscus (Fr, nom. sanct.) Quél. and O. fusconigra P.D. Orton. Different from us, he divided them into one scaly capped and three smooth-capped species. His O. sphagnicola seems to fit well with at least the lighter, if not both of our scaly capped species, and his concept of O. fusconigra seems to have a good fit for our Arr. telmaiaea. The remaining two epithets are a bit more difficult to fit to the species as we have outlined them. Current uncertainty in the community is illustrated even more dramatically in an on-line discussion (https://mushroomobserver.org/observer/show_ observation/89590, last accessed Mar 31, 2021): for a single collection, knowledgeable mycophiles considered four epithets, weighing three of them almost equally.
We were not aware of sphagnicolous species of Omphalina s. str., so that finding such a species (Fig. 5f, g) was a pleasant surprise. If there is a relationship with Sphagnum, it is facultative, because we find the same species much more frequently in boreal grasslands among low moss on poor soil. Despite the reputed reddish colouration of omphalinas, often this species was not separable macroscopically from a desquamated older Arr. gerardiana ( Fig. 3d; 4f), which can appear reddish at times, a non-blackish Arr. telmatiaea (Fig. 3f), or at times even from Arr. philonotis ( Fig. 3e; 5a, b). However, it can be separated from these readily by spore size (Fig. 6). So far, this is the only known species of the genus in NL. Our data have been made available to a colleague for phylogenetic type studies of the Omphalina pyxidata complex to identify this species, an undertaking outside the scope of the present study. To aid the reader, a brief description follows.
Because we have a large number of collections of sphagnicolous arrhenias from a wide geographic range (Table 3), the likelihood of finding additional species in accessible bogs of Europe or North America is low, but the existence of uncommon sphagnicolous species is possible in remote habitats outside usually surveyed regions. For example, in a report of 32 Nordic sphagnicolous agarics, Lange and Lange (1982) reported two very dark scaly capped sphagnicolous specimens from Greenland that they suspected might represent an unknown species. Spore measurements place them just outside the range of species in our study. As mentioned, we encountered two singleton species of Arrhenia, which we excluded from the current study due to lack of data. After concluding our study, we encountered another singleton in Sphagnum that we were unable to identify (DAOM984941, TUF117659 in Table 1, UDB038348; Voitk and Burzynski 2018). Thus, the possibility of finding additional sphagnicolous species in less commonly explored regions may not be exhausted.
Sphagnicolous omphalinoid arrhenias have been ignored in the era of molecular studies: in 2006, when we first began this investigation, we found only two sequences in GenBank identified with one of the names in our original list, one collection each. This experience demonstrates the major contribution of molecular analysis to taxonomy. Ranking organisms, we use their characters to separate them, but not all characters are equally relevant discriminators at all times. Sometimes cap ornamentation, colour, spore size, or ecology are excellent discriminators between species, while at other times some or all of these characters are irrelevant. Molecular studies identified four species clades, permitting retrospective examination, to learn which characters serve to separate these species and which do not. This requires familiarity with the organisms in their setting. A fresh comparison of protologues and original material to the characters of the identified clades will at times be rewarded with felicitous matches. We hope that this effort to identify the best name to match each clade without conflict, to fix each name with typification, and to circumscribe each species, will provide reliable guidelines for identification, and bring about lasting stability to this relatively small group of interesting fungi.