On Sistotremastrum and similar-looking taxa (Trechisporales, Basidiomycota)

The taxonomy of Sistotremastrum (Trechisporales, Basidiomycota) is revised based on morphology and DNA data. The genus is shown to be polyphyletic, and therefore it is split into two units—Sistotremastrum s. str. and Sertulicium, gen. nov. (typified with Corticium niveocremeum). Sistotremastrum s. str. is retained for eleven species of which eight are described as new while Sertulicium encompasses at least six species, including one new to science. Both of these genera are only distantly related to other representatives of the Trechisporales. Additionally, a new poroid neotropical species, Porpomyces abiens (Hydnodontaceae), is described as morphologically similar to some members of Sistotremastrum s. str.


Introduction
Sistotremastrum J. Erikss. is a genus of corticioid fungi typified with S. suecicum Litsch. ex J. Erikss. (Eriksson 1958). Initially introduced for two species, it has been gradually expanded to encompass smooth, effused basidiomycetes with clavate basidia producing four to six sterigmata and smooth, thin-walled, inamyloid basidiospores (Boidin and Gilles 1994;Telleria et al. 2013aTelleria et al. , 2014. Recently, Gruhn et al. (2018) described two new Sistotremastrum species with a hydnoid hymenophore and constantly four-sterigmatic basidia and thus changed the present concept of the genus. As a consequence, the morphological delimitation of Sistotremastrum from Brevicellicium K.H. Larsson & Hjortstam and, partly, from Trechispora P. Karst. became obscure. Another yet persisting problem is the separation of Sistotremastrum from Paullicorticium J. Erikss., which has a similar set of microscopic characters (Eriksson et al. 1984). Oberwinkler (1965) moved Sistotremastrum niveocremeum (Höhn. & Litsch.) J. Erikss., one of the original species, to Paullicorticium, stressing similarities in basidial development. Larsson et al. (2004) included Paullicorticium ansatum Liberta in Section Editor: Yu-Cheng Dai * Viacheslav Spirin viacheslav.spirin@helsinki.fi phylogenetic analyses of Agaricomycetes but were unable to place it in one of the clades currently recognized as orders. On the other hand, all Sistotremastrum species, including the generic type, have been found to be members of the Trechisporales Telleria et al. 2013aTelleria et al. , 2014Gruhn et al. 2018). However, most Paullicorticium species have not yet been studied by DNA methods-in particular, P. jacksonii Liberta whose connection to Sistotremastrum was discussed in the older literature (Eriksson et al. 1978). In the present paper, we revise the generic limits of Sistotremastrum and similar-looking taxa, and investigate species diversity based on collections from different regions of Eurasia, as well as from North and South America.

Morphological study
Type specimens and collections from herbaria H, O, LE, S, GB, MA, W, GENT, TRTC, LY, CWU, ANDA, MAN, SP, MG, SING, as well as from the private herbarium of the author JV were studied. Herbarium acronyms are given according to Thiers (2019). Microscopic methods follow Miettinen et al. (2018). All measurements were made from microscopic slides mounted in Cotton Blue (abbreviated as CB in descriptions below), using phase contrast and oil immersion lens (Leitz Diaplan microscope, × 1250 amplification). In total, 20-30 basidiospores, 20 basidia and subhymenial/subicular hyphae, and at least 10 basidioles and hyphidia were measured for each specimen studied. The following abbreviations are used in morphological descriptions: Lmean basidiospore length, W-mean basidiospore width, Q ′-length/width ratio, Q-mean length/width ratio, n-number of measurements per specimens.
DNA extraction, amplification, and sequencing DNA was extracted from herbarium specimens using the EZNA Forensic DNA kit (Omega Bio-tek) and AxyPrep Multisource Genomic DNA Miniprep kit (Axygen Biosciences, CA, USA) according to the manufacturer's instructions, except that 50 μl of the elution buffer was used in the elution step of the last one. The ribosomal ITS1-5.8S-ITS2 region was amplified and sequenced with the fungal specific primers ITS1F and ITS4B (Gardes and Bruns 1993). Sequences of nrLSU-rDNA were generated using primers LR0R, CTB6, LR5, and LR7 (Vilgalys and Hester 1990;Haynes et al. 1995). PCR products were visualized using agarose gel electrophoresis and Gel Red staining, and subsequently purified with the Fermentas Genomic DNA Purification Kit (Thermo Fisher Scientific, MA, USA). The resulting products were sequenced with an ABI model 3130 genetic analyzer (Applied Biosystems, CA, USA) and BigDye v.3.1 and ABI3730XL analyzer (Applied Biosystems) by Macrogen. The raw data were edited and assembled in MEGA 6 (Tamura et al. 2013).

Phylogenetic analyses
For this study, we generated 60 nrITS and 36 nrLSU sequences. All other sequences used in the analyses were downloaded from GenBank (Benson et al. 2018) or UNITE (Nilsson et al. 2018) ( Table 1). All newly generated sequences were deposited in the INSDC. Extremely high diversity of ITS sequences in the studied taxa precludes attempts to construct a reliable all-encompassing alignment for all Sistotremastrum spp. However, we could distinguish five alignable groups: S. niveocremeum complex, S. suecicum and its closest relatives, S. aculeocrepitans and its closest relatives, S. fibrillosum complex, and S. rigidum-vigilans clade. We found it reasonable to exclude S. fibrillosum, as well as newly described S. rigidum and S. vigilans from ITS analysis since molecular evidence provided by nrLSU analysis is sufficient for the purpose of our study. Therefore, we generated four alignments for this study: (1) nrLSU-alignment for the Trechisporales, (2) nrITS-alignment for S. niveocremeum, (3) nrITS-alignment limited to S. suecicum and its closest relatives, and (2) nrITSalignment for S. aculeocrepitans and its closest relatives. The alignments were calculated through MAFFT 7.429 online server (https://mafft.cbrc.jp/alignment/server/) using the L-INS-I strategy (Katoh et al. 2017) and then manually adjusted. The alignments are deposited in TreeBASE (S25768).
For the genus-level analysis, a nrLSU dataset (1) was assembled with representatives of Trechisporales (65 sequences). The resulting tree was rooted with Onnia leporina and Sphagnomphalia brevibasidiata (Hymenochaetales) and Sphaerobolus stellatus (Geastrales, Phallomycetidae). This choice was guided by the current JGI Basidiomycota tree (https://mycocosm.jgi.doe.gov/mycocosm/species-tree/tree;_ FJDxL?organism=basidiomycota) where Trechisporales is recovered close to Hymenochaetales and Phallomycetidae. After removing unalignable, ambiguous alignment positions, the alignment length was 742 bp with 184 variable site patterns. The three ITS datasets were assembled similarly: the S. niveocremeum species complex alignment (2) contained 60 sequences and had the length of 329 bp with 40 variable site patterns after removing unalignable, ambiguous positions. The S. suecicum species complex analysis (3) contained 22 sequences, with alignment length of 508 bp with 13 variable site patterns after removing ambiguous positions. The S. aculeocrepitans species complex analysis (4) contained 22 sequences with the alignment length of 470 bp with 37 variable site patterns. All the ITS trees are midpoint-rooted.
We inferred phylogenetic trees with maximum likelihood (ML), maximum parsimony (MP), and Bayesian inference (BI) but show here only the latter since all trees show  (Milne et al. 2008) based on the Akaike information criterion (AIC), which were GTR + G + I (nst = 6, rates = invgamma) for the nrLSUdataset, GTR+G (nst = 6, rates = gamma) for the S. niveocremeum dataset, and F81 (nst = 1) for the S. suecicum dataset. The suggested models were implemented in the Bayesian phylogenetic analyses. We performed Bayesian inference with MrBayes 3.2 (Ronquist et al. 2012).
In the analyses, three parallel runs with four chains each, temp = 0.2, were run for 3 million generations. All chains converged to <0.01 average standard deviation of split frequencies. A burn-in of 25% was used in the final analyses. Maximum likelihood (ML) analysis was performed in RAxML 7.2.8 (Stamatakis 2006) implemented in Geneious version 9.1.8 (http://www.geneious.com) (Kearse et al. 2012). Following models suggested by TOPALi 2.5, we preferred to use the GTR model with gamma correction (GTR GAMMA) in ML analysis. Bootstrapping was performed using the "Rapid bootstrapping" algorithm with the number of bootstrap replicates set as 1000. Maximum parsimony (MP) analysis was performed using SeaView version 4 (Gouy et al. 2010) with the ignoring all gap sites option. The number of bootstrap replicates was set as 1000.

Results
The nrLSU dataset encompasses all known genera of the Trechisporales as defined by Larsson et al. (2004) and , with addition of Pteridomyces and Suillosporium. The overall topologies of the Trechisporales were highly similar ( Fig. 1). They split the order into three strongly supported clades: (A) the Sistotremastrum s. str. subclade (pp = 1, bs = 99%) includes the generic type, S. suecicum, and two unnamed closely related species (introduced below as S. induratum and S. mendax), all with six-sterigmatic basidia, plus eight more distantly related species with four-sterigmatic basidia (S. aculeocrepitans, S. fibrillosum and six new species); (B) the S. niveocremeum subclade (pp = 1, bs = 100%) covers five species formerly considered as members of Sistotremastrum (except P. jacksonii and one unnamed taxon) but separated below into a new genus, Sertulicium. Morphological arguments for this solution are given in the taxonomic part of the present paper. Sistotremastrum guttuliferum is a younger synonym of Trechispora granulifera, and therefore designated as Sertulicium granuliferum in the phylogenetic trees; and (C) the Hydnodontaceae clade (pp = 1, bs = 99%) covers ten genera currently recognized in the family Liu et al. 2019). Among them, two sequences belong to an unnamed poroid fungus from French Guiana introduced below as Porpomyces abiens. Anatomically, its basidiocarps are confusingly similar to the four-sterigmatic Sistotremastrum species (i.e., S. aculeocrepitans, S. fibrillosum, and a number of new species described in this study) and differ from them mainly by a truly poroid hymenophore and smaller basidiospores. Sequences of three Brevicellicium species (including the generic type, B. exile) showing considerable morphological similarity to the four-sterigmatic Sistotremastrum species are also resolved in the Hydnodontaceae, in accordance to earlier studies Telleria et al. 2013b). Morphological traits differentiating Sistotremastrum s. str. from Brevicellicium and Trechispora are discussed in the taxonomic part of this paper. As for the family-level rearrangement of Sistotremastrum and Sertulicium, we address this question to further studies with the use of additional genetic markers.
Additionally, three ITS datasets were constructed for the new genus Sertulicium and the Sistotremastrum suecicum and S. aculeocrepitans complexes to clarify species limits with the use of larger amount of ITS sequences. The ITS-based topology of Sertulicium (Fig. 2) indicates a presence of up to ten species in the genus of which we have named six. Furthermore, ITS sequences of S. jacksonii and S. vernale reveal some differences (up to 1.4%) between European and extra-European material. This may indicate that both species, as they are here delimited, actually contain more than one taxon. However, more samples and genetic markers are needed to solve this problem. The second ITS-based phylogeny is restricted to the S. suecicum complex (Fig. 3). It shows the presence of at least two more species (described below as S. induratum and S. mendax) morphologically similar and phylogenetically close to the generic type of Sistotemastrum. The third ITS-based phylogram shows phylogenetic relationships of S. aculeocrepitans and up to five closely related species. Of them, three are described as new to science, all having four-sterigmatic basidia (S. aculeatum, S. denticulatum, and S. geminum) (Fig. 4). Four remaining Sistotremastrum species (S. confusum, S. fibrillosum, S. rigidum, and S. vigilans) dealt with in the present paper are represented in the nrLSU phylogeny ( Fig. 1). Their ITS sequences are available in GenBank (Table 1). Sequenced specimens are marked by asterisk. The genus was initially introduced as monotypic, encompassing only the type, Porpomyces mucidus (Pers.) Jülich (Jülich 1982). Larsson (2001) showed it is related to Trechispora. Another species, P. submucidus F. Wu & C.L. Zhao, was recently described from China (Wu et al. 2015). Here, we introduce the third representative of the genus, P. abiens from South America. From P. mucidus and P. submucidus, P. abiens differs by distinctly thick-walled and tightly arranged hyphae in subiculum and trama. This hyphal structure is clearly different from the loosely arranged, rather delicate, thin-or only slightly thick-walled hyphae of  branch lengths reflect estimated number of changes per site P. mucidus and P. submucidus. The two latter species have thin-walled basidia and no sterile hymenial elements while basidia are slightly thick-walled in a senescent hymenium of P. abiens and hyphidia are present. Rather tough basidiocarps consisting of predominantly thick-walled hyphae and short, tardily thick-walled basidia of P. abiens are reminiscent of hydnoid-semiporoid Sistotremastrum species, i.e., S. aculeatum, S. aculeocrepitans, and S. denticulatum. The only reliable anatomical traits differentiating them from P. abiens are their suburniform basidia and somewhat larger basidiospores. Moreover, no truly poroid species are so far known in Sistotremastrum s. str. Etymology. Abiens (Lat., part. from abeo)-departing, deviating.
Remarks. Porpomyces abiens has been detected in three localities in French Guiana. It seems to be a saprotrophic species occurring on wood remnants, various debris and soil. Specimens
Morphological differences between Sertulicium and Sistotremastrum s. str. cannot be easily grasped due to the extreme anatomical simplicity of their representatives. Nevertheless, some distinguishing characters are indicated here awaiting more in-depth analysis in the future. First, all but one Sertulicium spp. are extremely thin fungi consisting of a few subicular hyphae and the overlying subhymenium. The subicular hyphae are scattered; i.e., they do not produce hyphal strands so characteristic for most Sistotremastrum s. str. species studied by us. The only exception is Sertulicium granuliferum, having the most elaborate fructifications in the genus. Its basidiocarps start their development as radially arranged hyphal bundles becoming quickly covered by randomly arranged hyphae and finally indiscernible. In contrast, in Sistotremastrum s. str. subicular hyphal strands can be detected even in senescent basidiocarps if hyphae are not totally collapsed. Second, basidia in all Sertulicium spp. bear up to six sterigmata while at least some Sistotremastrum s. str. species are strictly four-sterigmatic. Moreover, apical parts of basidia in the latter genus often collapse, and hymenial cells of this kind dominate in well-developed and in senescent basidiocarps. Such apically collapsing basidia may occur in Sertulicium spp., too, but they are as a rule rare. Finally, all Sertulicium spp. have a smooth hymenial surface while about a half of the currently MB 833942 Sistotremastrum chilense was described from Patagonia (Telleria et al. 2014) as a relative of S. guttuliferum (see under Sertulicium granuliferum below). From the latter species, it differs primarily in having long-celled subhymenial hyphae (vs. short-celled and somewhat inflated in S. granuliferum). DNA data confirm its placement in Sertulicium.  (Miettinen 13310), and f S. suecicum (senescent basidiocarps) (Miettinen 14548) occasionally cracking in senescent basidiocarps. Margin first pruinose, later compact and rather sharply delimited. Small white patches spread at the marginal areas of young specimens, consisting of crystal agglomerations.
Remarks. This species was introduced as a member of Trechispora due to some morphological similarity to the smooth-spored members of that genus (i.e., Trechispora cohaerens group) (Hallenberg 1978). Larsson (1992) found clavate basidia with 4-5 sterigmata in the type collection and thus pointed towards possible affinities with Sistotremastrum. After rechecking the type, as well as morphological and DNA studies of newly collected material, we conclude that T. granulifera is an older name for the species recently introduced as Sistotremastrum guttuliferum (Telleria et al. 2013a). Consequently, a new combination is proposed. Sertulicium granuliferum differs from the similar-looking S. niveocremeum in having thicker and softer basidiocarps with a well-developed subicular layer and smaller basidiospores (Table 2).
Remarks. Paullicorticium jacksonii was described from Canada but later rarely treated as a species of its own. Eriksson et al. (1978) placed P. jacksonii among the synonyms of Sistotremastrum niveocremeum, and the species has been interpreted that way up to the present moment. Our data confirm that P. jacksonii is a good species belonging to Sertulicium. In addition to the type collection, we studied specimens from the USA and Europe.
Sertulicium jacksonii belongs to a difficult complex of extremely thin, conifer-dwelling species hardly distinguishable via morphological traits. Among them, S. jacksonii can be recognized by its wide subicular hyphae with variably thickened walls. Two similar-looking species, Sertulicium vernale and S. lateclavigerum, have narrower subicular hyp h a e t h a n t h o s e o f S . j a c k s o n i i . A d d i t i o n a l l y , S. lateclavigerum possesses narrower basidiospores than in the other two species (Table 2). However, the differences listed here were detected from a very restricted set of specimens. Further studies with broader sampling may improve our observations considerably. Paullicorticium ansatum Liberta, yet another morphologically similar although phylogenetically unrelated species, may be easily separated from Sertulicium spp. due to ansiform (loop-like) clamps and basidia with up to eight sterigmata.
We studied the holotype of S. lateclavigerum and observed basidia with 4-6 sterigmata only. In our opinion, the presence of globose or broadly clavate cystidia-like cells is insufficient as a single diagnostic character in Sistotremastrum s. l. We observed hymenial cells of the same shape in one collection of S. jacksonii (Laurila 3256b), in S. niveocremeum (Van Autgaerden S-20), as well as in three representatives of Sistotremastrum s. str. (holotype of S. geminum and two senescent collections of S. mendax and S. vigilans, respectively). On the other hand, another collection of S. lateclavigerum studied by us (Spirin 13457) is totally devoid of cystidia-like cells.
So far, S. lateclavigerum has been collected in France and Slovenia. However, environmental sequences in GenBank and UNITE point to a broader distribution area of this species. One of them came from Vietnam (MF942562)  Basidiocarps effused, initially pruinose, later compact, covering several cm, 0.03-0.1 mm thick. Hymenial surface whitish to cream-colored or pale ochraceous, smooth or porulose. Margin first pruinose, later compact and sharply delimited.
Remarks. Sertulicium niveocremeum is distributed in temperate-boreal Eurasia. It inhabits angiosperm hosts, mainly still attached or recently fallen branches but it may occur also on rather rotten wood. For a long time, S. niveocremeum has been mixed up with another angiosperm-dwelling species, S. granuliferum; their differences are discussed under the latter species. We studied the type material and a recent collection of Galzinia vesana from France; in our opinion, it is merely a monstrous form of S. niveocremeum with unusually long basidia and basidiospores, as well as occasionally branched sterigmata. DNA data from recently collected specimens confirmed this synonymy. While introducing G. vesana, Boidin and Gilles (1990) referred to a description and illustration of Galzinia sp. from Sweden (Eriksson and Ryvarden 1975: 398) as another possible record of that species. We re-checked the specimen illustrated by Eriksson and concluded that it belongs to Sertulicium, being morphologically most similar to S. niveocremeum. However, its exact identity is still uncertain, and it is therefore treated as Sertulicium sp. 2 under Specimens examined.
Some specimens of S. niveocremeum collected in the winter or spring are dominated by four-sterigmatic basidia. Only a few 5-6-sterigmatic basidia were detected in such specimens after meticulous study. Moreover, these collections usually have longer basidiospores than in most other specimens of S. niveocremeum (in particular, reaching 14.5 μm long in specimen Van Autgaerden S-20) and thus can be mixed up with Sistotremastrum vigilans. The latter species, introduced below, has constantly four-sterigmatic basidia and it occurs exclusively on coniferous hosts while S. niveocremeum seems to be restricted to angiosperms.
Specimens examined. Belgium. Antwerpen: Zoersel, Zoerselbos, deciduous wood, 16.V.2019 Van Autgaerden species by its narrower subicular hyphae and longer basidia. The species is so far known from two localities in Finland and two environmental sequence from Sweden (AY805625- Menkis et al. 2004) and CO, USA (JX136434- Huffman et al. 2013). The North American sequence is slightly different (2 bp) from the two European ones, and it may still belong to an undescribed sibling species.
The genus is redefined here to exclude members of the Sistotremastrum niveocremeum complex subsumed under Sertulicium. Differences between the two genera are discussed above. Extending Sistotremastrum s. str. with a number of four- sterigmatic taxa makes it difficult to delimit the genus from Brevicellicium and from smooth-spored Trechispora species. Trechispora differs by generally soft basidiocarps, short, often almost isodiametric subhymenial cells, and presence of ampullate septa on subicular hyphae. Brevicellicium species have similar subhymenial cells as in Trechispora but lack ampullate septa in the subiculum, which is poorly developed. Moreover, basidia in the four-sterigmatic Sistotremastrum spp. are more or less clearly suburniform, i.e., slightly constricted at the middle and narrowed at the apical part (except S. vigilans with exceptionally long, clavate-utriform basidia) while they are barrelshaped or short-clavate in Brevicellicium and Trechispora.
All but one four-sterigmatic representatives of the genus treated below are distributed in tropical areas. However, two unnamed sequences (CMH343, GenBank KF800434; 6S1.10.S04, GenBank EF619877) originated from the eastern part of the USA (Fig. 4). This could point towards more undescribed taxa in the four-sterigmatic species complex distributed in geographic regions with a cooler climate. Etymology. Aculeatus (Lat., adj.)-aculeate. Basidiocarps effused, first soft-floccose, then rather tough, covering several to tens of cm, 0.1-0.2 mm thick. Hymenial surface pale cream-colored to pale ochraceous, first warted, then odontioid, with irregularly arranged, sharp-pointed, partly fusing spines, 2-3 per mm, up to 2 mm long, or semiporoid, with shallow pores 0.5-1 per mm. Margin white to pale ochraceous, compact, in some portions with thin, white, pronounced hyphal strands. Smooth areas between spines fertile.
Remarks. Sistotremastrum aculeatum seems to be widely distributed in South-East Asia from China to Sumatra. Morphologically, it is most similar to the South American S. aculeocrepitans. It differs from the latter species mainly by longer spines, which tend to fuse together and produce shallow, wide pores.
Remarks. The species was introduced based on specimens from Martinique and French Guiana . We collected it in Brazil, and these specimens are the source of the present description. Differences of S. aculeocrepitans from S. denticulatum are treated under the latter species. Another similar-looking species from South America, S. fibrillosum Gruhn & Alvarado, has soft basidiocarps and densely arranged spines covering hyphal strands, and also considerably longer basidia. Sistotremastrum aculeocrepitans is reported here as new to Brazil. Etymology. Confusus (Lat., adj.)-confusing. Basidiocarps effused, soft, covering several cm, 0.04-0.07 mm thick. Hymenial surface whitish to cream-colored, smooth or irregularly tuberculate, accidentally cracking in old basidiocarps. Margin first arachnoid, with well-visible thin hyphal strands, later compact and rather clearly delimited.
Remarks. Sistotremastrum confusum is introduced here based on two sequenced collections from Brazil. Morphologically, it is most similar to S. vigilans distributed in Northern Hemisphere. The latter species has considerably larger basidia and basidiospores than those of S. confusum.
Remarks. Sistotremastrum denticulatum is morphologically most similar to S. aculeocrepitans but it has more densely arranged spines fusing together in characteristic fimbriate groups. Microscopically, these species are almost identical except for loosely arranged and not agglutinated hyphae in S. denticulatum. Sistotremastrum fibrillosum has spines not only on the hymenial surface but also on hyphal cords while S. denticulatum has sterile hyphal strands. The species is so far known only from the type locality in the southern part of Brazil.
Remarks. The description above is based on a single specimen from Brazil. Sistotremastrum fibrillosum was originally introduced from four specimens collected in French Guiana ). However, available DNA sequences show considerable variation, and this may indicate S. fibrillosum in the current sense is a collective species. More material is needed to find a more solid solution. Morphological differences of S. fibrillosum from S. aculeocrepitans detected in the same geographic region are treated under the latter species.
Remarks. Hymenophore with short warts (as opposed to long spines) and thin-walled, loosely arranged tramal hyphae differentiate S. geminum from other four-sterigmatic representatives of the genus treated here. The species is so far known only from the type locality in New Guinea. Etymology. Induratus (Lat., adj.)-hardening. Basidiocarps effused, initially pruinose, later compact, covering several cm, 0.03-0.1 mm thick. Hymenial surface whitish to cream-colored, smooth or porulose. Margin first pruinose, later compact and rather sharply delimited. Hyphal strands present in subiculum of vigorously growing specimens, tough and well-differentiated.
Remarks. Sistotremastrum induratum has so far been detected in two localities in the North American North-West. It is most similar to the European S. mendax but it has on average shorter basidia and basidiospores, as well as stable differences in ITS sequences. Distribution areas of the two species seem not to overlap.
Remarks. The species is introduced here as a sibling of S. suecicum occurring on wood of Picea in Europe. It differs from S. suecicum s. str. in having broader basidiospores and much better developed and easily observable hyphal strands in subiculum. Moreover, mature basidiocarps of S. suecicum are cracking in a characteristic way while they mostly stay continuous in S. mendax (Fig. 2). The host preference alone is not enough to recognize these species because S. suecicum sometimes occurs on spruce, as well as other coniferous trees. The author SV); the grant of the President of the Russian Federation (project MK-3216.2019.11) (the author SV); Societas pro Fauna et Flora Fennica (the author IV); Academy of Sciences of the Czech Republic (project number RVO: 60077344) (the author JV); Flemish Research Council (FWO) (grant number 11E0420N) (the author NS); Coordenação de Aperfeiçoamento Pessoal de Nível Superior -CAPES (Brazil) (the author VMV); The Rufford Small Grants Foundation (the author VMV).
Data availability DNA sequences used in the present study are available in GenBank. Alignments were deposited in TreeBASE. Fungal specimens are stored in public herbaria (as indicated under "Specimens examined").

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Conflict of interest The authors declare no competing interests.
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