Introduction

Xylodon (Pers.) Gray (Schizoporaceae, Hymenochaetales) is a large genus of corticioid fungi, having cosmopolitan distribution. The concept of this genus, as the main derivative of Hyphodontia sensu lato, was proposed by Hjortstam and Ryvarden (2007), and it was emended in subsequent publications, taking into account the results of molecular phylogenetic reconstructions (Riebesehl and Langer 2017; Viner et al. 2018; Riebesehl et al. 2019; Viner et al. 2023). Species of Xylodon inhabit dead wood of various sizes, from twigs several mm in diameter to large fallen trunks, and cause white rot. Sometimes basidiomata of Xylodon species appear on living parts of trees (Yurchenko 2008) and non-woody plant remains, e.g. fern rachises (Kotiranta and Saarenoksa 2000), herb stems and fallen leaves (Viner et al. 2018), dead polypore basidiomata (Viner et al. 2023). The genus is known from almost all types of world biomes where wooden plant debris occur, from humid to semiarid, and from seashore to upper limit of wooden vegetation in altitudinal gradient.

Riebesehl et al. (2019) showed that Xylodon species having minute aculei composed of clustered, projecting, encrusted, more or less firm-walled hyphal ends, belong to at least two groups: the X. lanatus species complex (also formulated as X. lanatus s. l.) and the X. hyphodontinus species complex. The phylogeny of the components of these complexes and some related species were considered in subsequent studies (Wang et al. 2021; Qu et al. 2022).

In the present work, new phylogeographic and morphological data for X. lanatus s. l. and Xylodon species with globose to broadly ellipsoid spores and tropical/subtropical distribution (including X. hyphodontinus) are considered, and four new species are described.

Material and methods

Morphology study

Specimens stored in herbaria BLS, CFMR, H, KAS, LY, MSK, O, SNP, SP, TNM (acronyms follow Thiers 2023) were examined during this study. Some specimens were duplicated, which is noted by ‘dupl.’ abbreviation before the herbarium acronym.

Macromorphology was studied on dried specimens. For micromorphology studies, slides of basidiomata sections prepared manually in 3% aqueous solution of potassium hydroxide (abbreviated as KOH), were used. Additional preparations were done in Melzer’s reagent (abbreviated as Mz) to study incrustations on hymenial elements and hyphae, and to test spore amyloid/dextrinoid reaction. In case of absence of both types of reaction, the abbreviation ‘Mz‒’ is used in protologues. Cyanophily of spores was examined in 0.02% cotton blue in 50% aqueous lactic acid (abbreviated as CB). Measurements of microstructures were done on a Nikon Eclipse Ni-U light microscope (Nikon Corp., Japan) by NIS-Elements Br imaging software (Nikon Corp.), mostly under ×1000 magnification. Mean spore length (L) and width (W) were calculated as arithmetic averages for 30 spores, randomly selected in squash preparations in KOH. Spore quotient (Q) was determined as length/width ratio for individual spores. Hymenophoral aculei density was measured by overlaying a scale line 1 mm long on photographs in 5 occasional places and calculating the number of aculei crossed by this line.

Scanning electron microscopy (SEM) studies were performed on a desktop microscope Phenom G2 pro (Labmate, UK). For this, pieces of basidiomata about 2×2 mm, taken from herbarium, were attached by double sided carbon adhesive discs (Leit tabs) to aluminium pin stubs, coated with 5–6 nm thick layer of gold in a Leica EN ACE200 vacuum sputter (Leica Microsystems, Germany), and examined at magnifications ×4100…×15500.

DNA extraction, amplification and sequencing

DNA was extracted from pieces of dried basidiomata 4‒16 mm2 in size with E.Z.N.A.® Fungal DNA Mini Kit (Omega Bio-Tek, VWR, Radnor, Pennsylvania, USA) following manufacturer’s instructions. These pieces were cut in the way to minimise the amount of substratum in the sample. For a part of specimens, total genomic DNA was extracted from dried fungi using a CTAB-chloroform extraction protocol (Kutuzova et al. 2017).

Nuclear ribosomal DNA ITS region, including ITS1, 5.8S RNA gene, and ITS2, were amplified with different combinations of primers ITS1F (Gardes and Bruns 1993), ITS1, ITS2, ITS3, ITS4, ITS5 (White et al. 1990), 58A1F (Martin and Rygiewicz 2005), LR22 (https://sites.duke.edu/vilgalyslab/files/2017/08/rDNA-primers-for-fungi.pdf) and ALR0.2 (Riebesehl and Langer 2017). The beginning D1-D2 domains of 28S rRNA gene were amplified with primers LR0R (Bunyard et al. 1996), LR5 (Vilgalys and Hester 1990), LR7 (Hopple and Vilgalys 1994), NL1, NL4 (O’Donnell 1993) and JS1 (Landvik 1996).

PCR products were purified with a DNA Clean & Concentrator®-5 kit (Zymo Research, Irvine, California, USA), then sequenced by LGC Genomics GmbH (Berlin, Germany). For some specimens, PCR products were purified from agarose gels using a Fermentas Genomic DNA Purification Kit (ThermoFisher Scientific, Waltham, Massachusetts); sequencing reactions were performed on an ABI 3730XL DNA analyzer (Applied Biosystems) by Macrogen (Amsterdam, the Netherlands).

The sequences were edited and assembled with MEGA11 (Tamura et al. 2021). Five quality check guidelines (Nilsson et al. 2012) were applied to them, after which sequences were deposited in NCBI GenBank (Benson et al. 2018, https://www.ncbi.nlm.nih.gov/genbank). Sequences, generated in this study, are listed in Table 1.

Table 1 Sequences used for phylogenetic reconstructions*
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Phylogenetic analysis

Additional sequences were downloaded from NCBI GenBank (Tab. 1). We collected in the datasets the available sequences of all Xylodon species (at least one representative for every species) represented in the database. Lyomyces sambuci, the type species of the closely related genus Lyomyces, was assigned as the outgroup for phylograms. The smaller subset, including the members of X. lanatus complex only, was composed to save more informative position for Maximum Likelihood (ML) calculations. Mid-point rooting was applied to the phylogram based on this smaller dataset. Datasets were created with MEGA11 and alignments were calculated with MAFFT v. 7 (Katoh et al. 2019; https://mafft.cbrc.jp/alignment/server), using L-INS-i algorithm for ITS and G-INS-i for 28S dataset. Bayesian inference of the phylogeny (BI) and ML method were used for tree building. Sequence alignments are available as supplementary material to this article. Dissimilarities between selected sequences were calculated by computing pairwise distances in MEGA11.

BI phylograms were computed with TrEase (Mishra et al., http://www.thines-lab.senckenberg.de/trease) using MrBayes v. 3.2 (Ronquist et al. 2012), using substitution models suggested by TOPALi v. 2.5 (Milne et al. 2008) and based on Akaike information criterion (AIC), one million generations, with a burn-in of 25% of trees to discard, and other parameters as default. FigTree v. 1.4.4 (Rambaut 2018; http://tree.bio.ed.ac.uk/software/figtree) was used for processing the BI phylograms. ML phylograms were calculated with MEGA11 under usage of substitution models based on AIC, suggested also by TOPALi v. 2.5. Bootstrap replications of 1000, and other settings as default were applied. Final versions of the phylograms were prepared in CorelDRAW v. 9 (Corel Corp., Ottawa, Canada, 1999).

Results

Phylogeny

Twenty-three ITS sequences from eight species and twelve 28S sequences from six species were generated in our study. The sequences of Xylodon lanatus s. str. (ITS and 28S), X. echinatus (ITS and 28S), and X. magnificus (28S) were obtained for the first time from these species. The oldest herbarium specimens from which ITS sequences of good quality were obtained, were 48 and 46 years old at the time of DNA extracting (CFMR HHB-4305, collected in 1970; O-F-904012, collected in 1974, respectively).

The final aligned ITS datamatrix consisted of 101 taxa and 824 positions. Some positions were manually adjusted based on their presumed homology, and where the L-INS-i algorithm did not result in optimal alignment. Also, some supposedly nonalignable positions were manually removed from the dataset. GTR+G model was suggested for BI and ML by TOPALi v. 2.5. Subsequently, model 6 (GTR) was chosen for the BI calculations with TrEase and GTR+G for the ML calculations with MEGA11.

The smaller aligned datamatrix, including the species related to X. lanatus only, consisted of 17 taxa and 667 positions. GTR+G model was suggested for BI and ML by TOPALi v. 2.5 for this dataset. Then model 6 (GTR) was chosen for BI calculations in TrEase, and GTR+G for ML calculations in MEGA11.

The final 28S alignment consisted of 81 taxa and 939 positions. GTR+I+G model was suggested for BI and ML by TOPALi v. 2.5. Subsequently, model 6 (GTR) was chosen for the BI calculations with TrEase and GTR+I+G for the ML calculations with MEGA11.

A high degree of agreement between BI and ML trees was observed for terminal clades, but deeper branching showed limited congruence (Figs. 1, 2, 4).

Fig. 1
figure 1

Bayesian inference of phylogeny of Xylodon species based on ITS sequences. Sequences obtained in this study are given in bold. The numbers above branches denote posterior probability (PP≥0.9) values for BI / bootstrap support (BS>75%) in ML phylogram; ‘-’ means the absence of the branch in ML phylogram. Scale bar shows the number of substitutions per site

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Fig. 2
figure 2

Continuing of the phylogram from Fig. 1

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The phylogeny revealed six distinct subclades in the X. lanatus species complex (all with PP = 1): (1) X. lanatus s. str.; (2) X. pseudolanatus; (3) X. kunmingensis; (4) X. mantiqueirensis; (5) X. echinatus; (6) X. afromontanus, based on a single specimen (Figs. 2, 3). ITS sequences of X. pseudolanatus demonstrate a high homogeneity: no more than 0.36% of dissimilarity. The maximum dissimilarity between ITS sequences in cluster X. lanatus s. str. reaches 1.45%. The subclades X. lanatus s. str., X. pseudolanatus, X. kunmingensis and X. echinatus are well distinguished in the 28S-based phylogeny too (Fig. 4). A specimen CFMR HHB-4305, treated earlier as paratype of X. lanatus s. str. (Riebesehl et al. 2019), after this phylogenetic study was belonged to X. pseudolanatus.

Fig. 3
figure 3

Bayesian inference of phylogeny of Xylodon lanatus species complex based on ITS sequences. Sequences obtained in this study are given in bold. The numbers above branches denote posterior probability (PP≥0.9) values for BI/bootstrap support (BS>75%) in ML phylogram; ‘-’ means the absence of the branch in ML phylogram. Scale bar shows the number of substitutions per site

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Fig. 4
figure 4

Bayesian inference of phylogeny of Xylodon species based on 28S sequences. Sequences obtained in this study are given in bold. The numbers above branches denote posterior probability (PP≥0.9) values for BI / bootstrap support (BS>75%) in ML phylogram; ‘-’ means the absence of the branch in ML phylogram. Scale bar shows the number of substitutions per site

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The ITS sequences of X. echinatus, derived from specimens collected in Borneo (KAS-JR31) and Java (H 7200350), have differences in 5 positions (0.85%). This study confirms that X. echinatus belongs to the X. lanatus species complex, as it was suggested earlier from the morphology (Riebesehl et al. 2019). Before the publication of X. echinatus (Yurchenko et al. 2013), S.H. Wu and co-workers failed to obtain sequences from the type material. Our attempts to obtain sequences from the holotype (TNM F24751) were also unsuccessful.

Our study contributed four new sequences to X. hyphodontinus (BLS M-5236, BLS M-5237; MSK-F 7397, MSK-F 11103), which grouped in a strongly supported clade (PP = 1) together with seven sequences, published earlier (Fig. 2). This clade demonstrates five phylogenetically distinct subclades in both phylogenies (Figs. 2, 4). Additionally, we obtained ITS2 sequence for X. hyphodontinus from Cameroon (O-F-907725). It is identical to the sequences of this segment for X. hyphodontinus from Kenya: there is a difference in a single bp between O-F-907725 and KAS-GEL9222, and no differences between O-F-907725 and H 7008787.

Three newly obtained sequences from South America form a well-supported clade (PP = 1), named here X. neotropicus. Two of them (BLS M-5233, BLS M-5234) originate from the same locality and one substratum unit in Ecuador, whereas SP467086 originates from Brazil. There are differences in 7 positions (including using the ambiguity code twice in BLS M-5234) between the ITS sequences of BLS M-5233 and BLS M-5234, and we suppose that these sequences were obtained from two genetically different, but neighbouring fungal individuals. NCBI BLAST for BLS M-5234 suggested X. hyphodontinus LR 12558 (91.02% similarity) and X. hastifer LR 19767 (88.94% similarity) as the most similar ITS sequences. The phylogenetic reconstructions (Figs. 2 and 4) demonstrated that X. neotropicus belong to the same clade as X. hyphodontinus (PP = 1).

The phylograms (Figs. 2 and 4) demonstrate that two sequences, called X. gloeocystidiifer, belong to the same clade (PP = 1) as X. hyphodontinus and X. neotropicus. NCBI BLAST suggested X. tropicus CLZhao 3397 (86.51% similarity) and X. ramicida Spirin 7670 (86.36% similarity) as the most similar ITS sequences for X. gloeocystidiifer BLS M-5232.

The inclusion of 28S rRNA gene barcode of a specimen collected from New Zealand and identified as X. magnificus in our phylogenetic reconstruction confirmed that this species is related to X. pruinosus and X. detriticus (Fig. 4) as suggested by Viner et al. (2018). All three taxa were previously classified in Lagarobasidium.

Morphology

The complex phylogenetic structure of X. lanatus s. l., observed in our study, opened the questions how to treat the subclades within this complex in terms of morphology. At the same time, the attempts to obtain DNA barcodes from X. lanatus holotype (CFMR HHB-8925) by Riebesehl et al. (2019) were not successful. To understand better the taxa within X. lanatus s. l., both in terms of morphology and molecular phylogeny, we introduce here an epitype for X. lanatus, supported by sequence data. The selected epitype was collected close to the locus classicus, though 5 years later than the holotype, and from a similar kind of substratum. The epi- and holotype are morphologically highly similar. The description of X. lanatus s. str., based on the three specimens from continental North America, is given below. The exclusion of two specimens of X. lanatus, collected in tropical areas, is explained in the ‘Discussion’ section.

The specimens nested in the subclade of X. lanatus s. str. (Figs. 2 and 3) are morphologically similar to X. lanatus holotype and epitype, except H 7200692. The latter has a poorly developed, discontinuous subiculum, fragile aculei, and it lacks a well-developed sterile margin (Fig. 5b). According to these macroscopic features, it is close to the holotype of X. pseudolanatus (see Riebesehl et al. 2019). A similar discrepancy was observed for H 7200690, nested within the X. pseudolanatus subclade. This specimen has a well-developed subiculum and sterile margin, like in X. lanatus s. str. (Fig. 5c). Thus, we conclude that subiculum and margin morphology in X. lanatus and X. pseudolanatus may be affected by growth conditions. However, we have found a difference in hymenophoral aculei size: within an individual basidioma the aculei are in average smaller in X. pseudolanatus (see the key below). Moreover, aculei in X. pseudolanatus are less bristly, with more compactly arranged hyphoid cystidia, than in X. lanatus.

Fig. 5
figure 5

Macromorphology of Xylodon lanatus s. l. a X. lanatus, epitype (CFMR FP-101864-A); b X. lanatus (H 7200692); c X. pseudolanatus (H 7200690); d X. afromontanus, holotype (O-F-904012); e X. mantiqueirensis, isotype (H 7075551); f X. echinatus (H 7200350). In a‒d, f the upper images show central part of basidioma, lower images show the margin of basidioma. Scale bars = 1 mm

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Thorough microscopy for tens of sections of specimens belonging to the different subclades of X. lanatus s. l. showed that spore morphology (Fig. 6) and cystidial morphology can be used to distinguish species, which together with phylogenetic evidence allowed us to describe two more species in this complex: X. afromontanus (Fig. 5d) and X. mantiqueirensis (Fig. 5e).

Fig. 6
figure 6

Basidiospores in the Xylodon lanatus species complex. a X. lanatus, epitype (CFMR FP-101864-A); b X. lanatus (KAS-Ec720); c X. pseudolanatus (CFMR HHB-4305); d X. pseudolanatus (H 7200690); e X. afromontanus, holotype (O-F-904012); f X. mantiqueirensis, isotype (H 7075551); g X. echinatus (H 7200350). Scale bar = 5 μm

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We have found two specimens from Borneo and one from Java, which fit in most morphological features to the protologue and to the holotype of X. echinatus (Fig. 5f). The specimen from Java (H 7200350) differs from the original description of X. echinatus by slightly smaller spores, (4.5‒)5‒5.8 × (3.3‒)3.5‒4(‒5) μm. The specimens from Sunda Archipelago also have fewer echinulate crystals on projecting hyphae, than in the holotype (Fig. 7).

Fig. 7
figure 7

SEM images of crystalline deposits on projecting hyphae in hymenophoral aculei of Xylodon lanatus s. l. a X. lanatus, holotype (CFMR HHB-8925); b X. pseudolanatus, holotype (CFMR FP-150922); c X. afromontanus, holotype (O-F-904012); d X. mantiqueirensis, isotype (H 7075551). e X. echinatus, holotype (TNM F24751); f X. echinatus (H 7200350). Scale bars = 5 μm

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After studying the holotype of Pteridomyces sphaericosporus Boidin, Lanquetin & Gilles (LY 7377), we found it identical in cystidial, hyphal and spore morphology with Xylodon hyphodontinus, depicted in Riebesehl et al. (2019, Fig. 6), and so re-affirm that P. sphaericosporus is a synonym of X. hyphodontinus.

In the present study we have distinguished two more species, collected in South America, with globose to broadly ellipsoid spores and an odontioid hymenophore. The specimens BLS M-5234, BLS M-5235, collected in Ecuador, and SP467086, collected in Brazil, demonstrated such high degree of morphological similarity, that we classify them in one species, X. neotropicus, which is supported by the phylogenetic analyses. The species, found in Ecuador and named X. gloeocystidiifer, is represented by two specimens, BLS M-5232 and EYu 190720-11 (CFMR), which are identical in most macroscopic and microscopic features, but do not fit to any earlier described species of Xylodon. The protologues of X. neotropicus and X. gloeocystidiifer are given in the ‘Taxonomy’ section.

We carried out SEM study of crystalline deposits on projecting hyphae (hyphoid cystidia) of Xylodon species (Fig. 7). With this, we aimed to find additional features to distinguish species in X. lanatus s. l. The specimens of X. lanatus (CFMR HHB-8925, CFMR FP-101864-A, CFMR FP-102919, H 7200692), X. pseudolanatus (CFMR FP-150922, H 7200690), X. afromontanus (O-F-904012, H 7006854), X. mantiqueirensis (H 7075551) and X. echinatus (TNM F24751, H 7200350) were examined. Plate-like crystals, 2‒4 μm in diameter, with serrate margins, aggregated in rose-shaped structures, were observed in all listed specimens as the predominating morphological type of deposits. Morphological differences for these crystals were small: they were more aggregated in stacks and not so rose-shaped in X. afromontanus (Fig. 7c), and on average smaller (about 2 μm diam.) in X. mantiqueirensis (Fig. 7d). Moreover, crystals without serrate margins were observed in X. echinatus (Fig. 7f) and X. afromontanus. Bipyramidal crystals were rare on hyphoid cystidia (Fig. 7b, c, f), but were more common on subicular hyphae.

Taxonomy

Xylodon lanatus (Burds & Nakasone) Hjorstam & Ryvarden

Basionym: Hyphodontia lanata Burds & Nakasone, Mycologia 73: 461 (1981).

Epitype (designated here, MycoBank Typification No.: 10013103): USA. Mississippi, Harrison County, De Soto National Forest, Harrison Experimental Forest, 30.6305° N, 89.0456° W, on dead hardwood, leg. K.K. Nakasone, 5 Nov 1981 (CFMR FP-101864-A; Figs. 5a, 6a).

Basidiomata effused, fragile membranaceous. Subiculum continuous, 70‒170 μm thick, of open, woolly texture, pale brownish yellow. Hymenial surface odontioid, cream-coloured; aculei irregularly conical or irregularly cylindrical, 4‒6/mm, (40‒)65‒200 μm high, (30‒)60‒140(‒170) μm diam. at base, (25‒)30‒95 μm diam. in the middle part. The part between aculei continuous, 60‒200 μm thick. Margin woolly, 1‒1.5 mm wide, of the same colour as hymenial surface. Hyphal system monomitic, hyphae colourless, clamped at all primary septa. Subicular hyphae sparingly branched, 2‒4 μm wide, with some inflations up to 5‒6 μm wide, thin- to thick-walled (wall up to 1 μm thick), smooth or with isodiametric crystals, 1.5‒4(‒7) μm across, scattered between hyphae. Subhymenial hyphae moderately to richly branched, (1.3‒)1.7‒3 μm wide, moderately thin-walled under basidia, slightly thick-walled in lower subhymenium, smooth to fairly richly encrusted by crystals reaching 5‒12 μm across. Projecting hyphae at aculeal apices (hyphoid cystidia) mostly collected in clusters, almost straight to flexuous, 20‒50 × 2.3‒4 μm, thin- to thick-walled (wall up to 1.3 μm thick), even or with some constrictions, loosely encrusted, predominantly near apex, sometimes smooth. Immersed capitate or clavate-capitate cystidia (vesicular structures) 10‒40 × (4‒)5‒8.5(‒9) μm, often with 1‒4 adventitious septa, thin- to thick-walled (wall in swollen part up to 1.5 μm thick). Capitate cystidia in hymenium rare, 13‒30 × 3‒5 μm, thin-walled. Basidioles subcylindrical to clavate, (8‒)12‒20(‒27) × 3.2‒4.5(‒5.5) μm, thin-walled, smooth or poorly encrusted. Basidia narrowly utriform, thin-walled, smooth, 20‒25 × 3.5‒4 μm, with four sterigmata 2‒2.5 × 0.5 μm. Basidiospores narrowly ellipsoid to oblong, (4.5‒)5.3‒5.7(‒6) × (2.5‒)2.7‒3.5 μm (in epitype L = 5.3 μm, W = 2.9 μm), Q = 1.7‒2.2, barely thick-walled, Mz‒, acyanophilous, with very short or unclear apiculus.

Remark: In holotype (CFMR HHB-8925) basidiospores are 4.5‒5.5 × 2.5‒3(‒3.3) μm, with L = 4.95 μm and W = 2.8 μm.

Additional specimens examined: USA. Mississippi, Harrison County, De Soto National Forest, ‘Hammock Road H 4-Harrison Experimental Forest’, on dead wood of Liriodendron tulipifera, coll. H.H. Burdsall, Jr., 1 Apr 1976 (CFMR HHB-8925, holotype); North Carolina, Brunswick County, Green Swamp Preserve, swamp forest with canopy of Pinus with admixture of Acer rubra, on fallen branch of angiosperm, leg. O. Miettinen, 16 Nov 2013, OM 17683 (H 7200691); Florida, Alachua County, Gainesville, Sweetwater Preserve, middle-aged mixed forest, on dead wood of angiosperm, leg. O. Miettinen, 22 Nov 2013, OM 17835.3 (H 7200692); Puerto Rico, Maricao Commonwealth Forest, Near Maricao Recreation Area, 18.1723° N, 66.9861° W, on dead wood, leg. K.K. Nakasone, 25 Jun 1996 (CFMR FP-102919-Sp). Ecuador. Zamora Chinchipe Province, the vicinity of Estación Científica San Francisco, Permanent sample plot No. 5, about 1850 m a.s.l., on log with no contact to ground, leg. E. Langer, 8 Mar 2002 (KAS-Ec720).

Xylodon afromontanus Yurchenko & Viner, sp. nov.

Figs. 5d, 6e, 7c.

MycoBank No.: MB848555.

Etymology: the specific epithet stresses the origin of the type material from mountains of Africa.

Holotype: Rwanda. Western Province, Nyungwe Forest National Park, trail from Pindura to Mount Bigugu, 2750 m a.s.l., on decayed corticated branch, leg. J. Rammeloo, 29 Jul 1974, No. 4115 (O-F-904012; isotype H 7006811).

Basidiomata effused, 2–4 and more cm in extent, fragile membranaceous, between aculei loose, 60–140 μm thick. Hymenial surface odontioid, pale cream to cream-coloured; aculei irregularly conical, usually fimbriate, 50–85 μm high, 40–85 μm diam., 5‒7/mm. Margin thinning out or mould-like, 0.1–0.5 mm wide, concolourous or paler than fertile part of basidioma. Hyphal system monomitic, hyphae clamped at all septa, moderately branched, colourless. Subicular hyphae 2.5–3.5 μm wide, with scattered inflations up to 9 μm wide, with thickened or thick (up to about 1 μm) walls, smooth or scarcely incrusted. Subhymenial hyphae (2–)2.5–3.2 μm wide, walls thin, sometimes thick near subiculum, smooth or encrusted by crystals 2–3 μm across. Projecting hyphae (hyphoid cystidia) almost straight to flexuous, 30–50(–80) × (2–)2.5–3.5 μm, smooth to encrusted, especially in upper part, thin- to thick-walled (wall up to 1 μm thick), without or with occasional constrictions. Cystidia rare, capitate and clavate, (13–)25–35 × 5–8 μm, thin-walled in apical part, lacked adventitious septa; also present cystidia little differentiated from hyphal ends (subcapitate and subclavate). Basidioles clavate, subcylindrical, occasionally subcapitate, (7–)15–23 × 4–5 μm, smooth or slightly encrusted. Basidia narrowly utriform, 20‒25(–30) × 4‒4.5(–5) μm, thin-walled, smooth or slightly encrusted, with four sterigmata 2.5–3.5 × 1 μm. Basidiospores broadly ellipsoid (Q = 1.3) to narrowly ellipsoid (Q = 1.8‒2.2), with a prevalence of ellipsoid ones (Q = 1.5‒1.6), (4.3‒)5‒6(‒6.5) × 3‒4 μm, thin-walled, Mz–, acyanophilous; apiculus very short or unclear.

Distribution and ecology: The species occurs in Eastern Africa, in Afromontane rainforests at the elevations about 1800‒2800 m a.s.l. and grows saprobically on dead wood.

Remarks: A notable feature of this species is the presence of variable, broadly ellipsoid to narrowly ellipsoid basidiospores, within the same basidioma. In the holotype spores are (4.3‒)4.7‒6 × 3‒4 μm (L = 5.2 μm, W = 3.5 μm), in the paratype they are 5‒6(‒6.5) × 3‒4 μm (L = 5.6 μm, W = 3.5 μm). The distinctions of this species from other members of X. lanatus complex are described in the key below.

Additional specimen examined: Malawi. Southern Region, Mulanje distr., Mulanje Massif, Lichenya Plateau, 1800‒2000 m a.s.l., on dead decorticated wood, leg. L. Ryvarden, 9‒10 Mar 1973, No. 11416 (O-F-904167; dupl. H 7006854).

Xylodon mantiqueirensis Yurchenko, Motato-Vásq. & Viner, sp. nov.

Figs. 5e, 6f, 7d.

MycoBank No.: MB848556.

Etymology: mantiqueirensis = occurring in the Mantiqueira Mountains (Serra da Mantiqueira), a chain northeast of São Paulo.

Holotype: Brazil. São Paulo State, the vicinity of Campos do Jordão, Parque Estadual Campos do Jordão, Celestina trail, Araucaria forest, on dead decaying branch, leg. V. Motato-Vásquez, A.M. Gugliotta, J. Cabra-García, 14 Oct 2015, MV529 (SP467059; isotype H 7075551).

Basidiomata effused, 10–15 and more cm in extent, membranaceous, between aculei slightly cracking, 180–250 μm thick. Hymenial surface odontioid, cream-coloured; aculei conical or subcylindrical, often fimbriate apically, 60–180 μm high, 30–75 μm in diam., 4‒7/mm. Margin fimbriate to woolly, 0.5–1 mm wide, concolourous or paler than the fertile part of basidioma. Hyphal system monomitic, hyphae clamped at all septa, colourless. Subiculum loose, woolly; subucular hyphae moderately branched, 2.7–4(–4.5) μm wide, with thickened or thick (up to 1.3 μm) walls, smooth. Subhymenial hyphae moderately to richly branched, 2–3 μm wide, walls thin or slightly thickened near subiculum, smooth or scarcely encrusted. Projecting hyphae (hyphoid cystidia) almost straight to flexuous, (25–)30–50(–80) × 2.5–3.5(–4) μm, smooth to encrusted, especially in upper part, thin- to thick-walled (wall up to 1 μm thick), with scattered constrictions. Cystidia capitate, 20–35 × (5–)5.5–9 μm, with 0–2 adventitious septa, in capitate part thin- or slightly thick-walled. Basidioles clavate, subcapitate, capitate, rarely subcylindrical, (10–)13–25 × 3.5–6.5 μm, smooth. Basidia narrowly utriform, 17–31 × 4–4.5 μm, thin-walled, smooth. Basidiospores from broadly ellipsoid (Q = 1.4) to predominantly narrowly ellipsoid (Q = 1.6–1.7), 5‒6 × (2.5‒)3‒3.5 μm (in holotype L = 5.3 μm, W = 3.1 μm), Mz–, acyanophilous; apiculus short or unclear.

Distribution and ecology: The species is known so far from tropical montane forests in the southeastern Brazil; it grows saprobically on dead wood.

Remarks: A distinctive feature of this species is common subcapitate and capitate thin-walled elements in hymenium, which can be treated as basidioles or small cystidia. Basidiospores in this species are of variable shape within the same basidioma. In contrast to X. afromontanus, ellipsoid spores (Q = 1.4–1.5) in X. mantiqueirensis are few. Other distinctions of X. mantiqueirensis from the members of X. lanatus complex are described in the key below.

Additional specimen examined: Brazil. São Paulo State, the same address as holotype, Araucaria forest, on decaying wood, leg. V. Motato-Vásquez, A.M. Gugliotta, J. Cabra-García, 14 Oct 2015, MV509 (SP498889).

Key to the species of Xylodon lanatus complex

  • 1. Ellipsoid to broadly ellipsoid basidiospores (Q = 1.3–1.5) present, from rare to common … 2

  • - Spores with Q = 1.3–1.5 absent or occasional; most spores ellipsoid to narrowly ellipsoid and short cylindrical (Q = 1.6–2.1) … 4

  • 2.Capitate cystidia with thick wall and/or adventitious septa absent; pronounced constrictions on projecting hyphae (hyphoid cystidia) absent or occasional … 3

  • - Some capitate cystidia with thick wall and/or adventitious septa; pronounced constrictions present on some projecting hyphae (hyphoid cystidia); the species found in the eastern part of South America … X. mantiqueirensis

  • 3. Basidioma between aculei often more than 150 μm thick, up to 350 μm thick; sterile margin woolly, continuous; species, occurring in Southeast Asia … X. echinatus

  • - Basidioma between aculei usually less than 140 μm thick; sterile margin thinning out, discontinuous; species, occurring in eastern Africa … X. afromontanus

  • 4. Hymenophoral aculei 0.13–0.35 mm long, 4 per mm; species, occurring in New Zealand … X. vesiculosus

  • - Hymenophoral aculei 0.05–0.125 mm long, 4–9 per mm; species from North America, South America and Southeast Asia … 5

  • 5. Projecting hyphae (hyphoid cystidia) mostly flexuous and with distinct constrictions, with thin or thickened walls; Asian species … X. kunmingensis

  • - Projecting hyphae (hyphoid cystidia) mostly straight or somewhat wavy and without constrictions; if constricted, then with thickened or thick walls; American species … 6

  • 6. Well-developed hymenophoral aculei 60–140 μm in diameter at base and 30–95 μm in diameter in the middle part; all spores ellipsoid to narrowly ellipsoid, Q = 1.6–2.1 … X. lanatus s. str.

  • - Well-developed hymenophoral aculei 40–90 μm in diameter at base and 30–60 μm in diameter in the middle part; some spores almost broadly ellipsoid (Q = 1.4–1.5) … X. pseudolanatus

Xylodon neotropicus Yurchenko, Motato-Vásq. & Viner, sp. nov.

Figs. 8, 9.

Fig. 8
figure 8

Macromorphology of Xylodon neotropicus. a A basidioma in type locality of the species; b isotype (H 7075552), basidioma in central part; c isotype, periphery of basidioma; d paratype (BLS M-5234). Scale bars = 1 mm

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Fig. 9
figure 9

Micromorphology of Xylodon neotropicus (isotype, H 7075552). a Vertical section through basidioma; b hyphae of aculeal trama; c portion of hymenium and subhymenium; d subbasidial hyphae with rough surface; e peg-like aggregate of hyphae; f individual hyphae projecting from the hymenium; g fusoid cystidia; h cylindrical and subcylindrical cystidia; i capitate cystidia; j basidioles; k basidia; l basidiospores. b, c, e‒l preparations in KOH; d preparation in Mz. Scale bars = 1 mm for a, 10 μm for b‒k, 5 μm for l

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MycoBank No.: MB848557.

Etymology: neotropicus (Lat.) = occurring in the Neotropics.

Holotype: Brazil. Rio de Janeiro State, Serra da Mantiqueira Mts., Parque National do Itatiaia, Três Picos trail, 22.3483°S, 44.6208°W, Atlantic rainforest, on dead decaying corticated branch, leg. V. Motato-Vásquez, A.M. Gugliotta, 27 Nov 2015, MV580 (SP467086; isotype H 7075552).

Basidiomata effused, membranaceous, fairly tough in old state, up to 5 and more cm long, 0.1–0.2 mm thick between aculei. Margin thinning out. Hymenial surface odontioid to short hydnoid and almost irpicoid, from yellowish with ochraceous tinge to ochraceous. Aculei conical or flattened, subirpicoid, about 2.5/mm, partly confluent at bases, up to 1 mm high, 0.2–0.8 mm wide. Hyphal system monomitic, hyphae clamped at all primary septa, colourless or yellowish in mass. Subicular and tramal hyphae (1.7–)2.5–3.5(–4.5) μm wide, thin- to mostly thick-walled (walls up to 1 μm thick), smooth or with scarce coarse crystals 8–12 μm across. Subhymenial hyphae richly branched, 1.2–3.5(–4.3) μm wide, with short and somewhat swollen segments, thin- to slightly thick-walled towards subiculum, smooth or with minutely rough surface. Hymenial surface with numerous projecting peg-like aggregates of loosely encrusted hyphae, 35–70 μm long, 13‒22 μm wide, giving to the aculei asperulate or setose appearance under a lens; individual hyphal ends in pegs thin-walled, (1.8‒)2.3–3.2 μm wide, 3.5–4.5 μm wide with incrustation, apically cylindrical or slightly narrowing. Cystidial elements (cystidioles) in hymenium thin-walled, of three types: (1) fusoid rare, smooth, 13–21 × 3.5–5.5 μm; (2) cylindrical or subcylindrical rare, 12–21 × 3.5–4.5 μm, often widened at base, smooth or scarcely encrusted; (3) capitate rare, 10–16.5 × 3.5–4.5 μm, smooth. Basidioles from ovoid to subcylindrical, 5.5‒15(–18) × 3‒5 μm, smooth. Basidia subcylindrical-subutriform, 11–12 × 3.5–4.3 μm; sterigmata four, about 2.5 × 0.5 μm. Basidiospores globose to subglobose, 3.5–4(–4.5) × 3.3–3.7(–4) μm (in holotype L = 3.85 μm, W = 3.55 μm), thin- to slightly thick-walled, colourless, Mz–, acyanophilous; apiculus short and blunt, distinct, sometimes unclear.

Distribution and ecology: The species is known from northeastern Ecuador and southeastern Brazil, and grows on dead branches. The natural range of this species supposedly covers the part of South America where tropical humid forests occur.

Remarks: The species is morphologically most close to X. hyphodontinus due to clusters of projecting encrusted hyphae, fusoid cystidia (cystidioles), inflated hyphae in subhymenium, and globose basidiospores. However, X. neotropicus has much larger hymenophoral aculei, and ochraceous colour or hymenial surface, which was never noted in X. hyphodontinus. BLS M-5233 is a form of X. neotropicus, which differs from three other specimens of this species by the presence of scattered, shortly clavate and pyriform basidioles 6.5–9 × 4.5–5.5 μm, covered by crystalline encrustations.

Additional specimens examined: Ecuador. Orellana Province, near Flor de Oriente village, 0.5042°S, 76.9819°W, 295 m a.s.l., equatorial rainforest in hilly area, on fallen branch, leg. E. Yurchenko, 21 Jul 2019, EYu 190721-12a (BLS M-5235), EYu 190721-12b (BLS M-5234); between Puerto Francisco de Orellana and El Dorado, right bank of the Napo river, 0.4861°S, 76.9500°W, 260 m a.s.l., Amazonian rainforest, on dead hanging decorticated branch, leg. E. Yurchenko, 20 Jul 2019, EYu 190720-12a (BLS M-5233).

Xylodon gloeocystidiifer Yurchenko & Riebesehl, sp. nov.

Figs. 10, 11.

Fig. 10
figure 10

Habitat and macromorphology of Xylodon gloeocystidiifer. a Substratum of the holotype (BLS M-5232) in situ (marked *); b, c holotype; d paratype (EYu 190720-11 (CFMR)). Scale bars = 1 mm

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Fig. 11
figure 11

Micromorphology of Xylodon gloeocystidiifer. Holotype (BLS M-5231): a, b vertical sections through basidioma; c, d agglutinated hyphal ends at aculeal apices; e subicular hyphae; f basidioles and subhymenial hyphae; g hyphal ends from aculei; h capitate cystidia; i broken tips of capitate cystidia; j, k capitate cystidia with excreted cap; l gloeocystidia; m basidia; n, o basidiospores. Paratype (EYu 190720-11 (CFMR)): p excreted caps on capitate cystidia and detached from them; q gloeocystidia-like capitate elements. b‒j, l‒n, q preparations in KOH; k, o preparations in Mz, p preparation in CB. Scale bars = 100 μm for a, 20 μm for b‒d, 10 μm for e–m, p, q; 5 μm for n, o

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MycoBank No.: MB848558.

Etymology: gloeocystidiifer (Lat.) = bearing gloeocystidia.

Holotype: Ecuador. Orellana Province, near Flor de Oriente village, 0.5042°S, 76.9819°W, 295 m a.s.l., equatorial rainforest in hilly area, on large fallen decaying leaf, leg. E. Yurchenko, 21 Jul 2019, EYu 190721-61 (BLS M-5232).

Basidioma effused, 0.5–1.5 cm in extent, membranaceous, minutely odontioid; the part between aculei loose, discontinuous, 50‒120 μm thick, white. Aculei 5‒6/mm, conical, simple or branched/aggregated, fimbriate, often apically attenuated, 70‒180 μm long, 70‒140 μm diam., from white to yellowish and pale ochraceous. Margin more or less thinning out. Hyphal system monomitic, hyphae clamped at all septa, colourless, but tramal hyphae becoming yellowish in mass with age. Subicular hyphae sparsely branched, colourless, thin- to thick-walled (wall up to 0.8 μm thick), 2.3‒3.5 μm wide; coarse crystals up to 10‒15 μm across scattered between hyphae. Tramal hyphae sparsely branched, more or less parallel (vertically arranged), 2‒3 μm wide, thin- to slightly thick-walled, smooth or slightly encrusted, colourless or yellowish in mass, protruding in aculeal apices as bundles of hyphal ends; hyphae in these bundles 2.5‒4.3 μm wide, usually agglutinated, smooth, apically rounded, rarely subcapitate, capitulate (capitulus about 2 μm wide) or collapsed and then tapering. Subhymenial hyphae moderately or richly branched, 1.8‒3 μm wide, thin-walled, smooth or scarcely encrusted. Cystidia of two types: (1) capitate numerous, colourless to yellowish, 12‒20 × 3‒4 μm, with fragile apex 4‒5 μm wide; apical swelling slightly refractive, in older basidiomata supplied by a cap of resinous matter 9‒12 μm wide; caps preserved in water and CB, but easily dissolving in KOH; (2) gloeocystidia subcylindrical or fusoid, 10‒30(‒35) × (4‒)5‒6(‒6.5) μm, slightly refractive and pale yellowish in KOH, with the contents becoming coloured in Mz and CB. Basidioles ovoid, short clavate, subcylindrical, 6.5–13 × (3.2‒)3.5–4.3 μm, colourless to yellowish. Basidia subcylindrical or subutriform, 10‒18.5 × (3‒)3.3‒4.3 μm; sterigmata four, 1.7–3.5 × 0.3–0.5 μm. Basidiospores globose to broadly ellipsoid, mostly subglobose, (3.2‒)3.5‒4(‒4.5) × 2.8‒3.5(‒3.7) μm (in holotype L = 3.9 μm, W = 3.3 μm), slightly or unclearly thick-walled, colourless, Mz–, acyanophilous; apiculus minute, narrow or little pronounced.

Distribution and ecology: The known localities are in northeastern part of Ecuador, in zone of Amazonian rainforest, the Napo river basin. The fungus grows saprobically on wooden and non-wooden remains, like decayed leaves.

Remarks: In hymenium of this fungus there are also elements, intermediate in morphology between basidioles and gloeocystidia, basidioles and capitate cystidia, gloeocystidia and capitate cystidia. Thickened spore wall is more clearly visible in Mz.

There are several species of Xylodon, possessing, like X. gloeocystidiifer, cylindrical/subcylindrical cystidia and capitate cystidia with resinous caps: X. brevisetus, X. crassisporus, X. spathulatus, X. subclavatus. The main differences of these from X. gloeocystidiifer are: much loose texture of aculei and ellipsoid spores in X. brevisetus, longer leptocystidia and ellipsoid spores in X. crassisporus, loose arrangement of hyphae at apices of aculei and cystidia with narrowed tips in X. spathulatus, moniliform cystidia in X. subclavatus. Besides, the new species has similarities with X. follis, but the latter has projecting hyphae with crystalline incrustation, vesicular basidioles and much larger spores.

Additional specimen examined: Ecuador. Orellana Province, between Puerto Francisco de Orellana town and El Dorado village, right bank of the Napo river, 0.4861°S, 76.9500°W, 260 m a.s.l., equatorial rainforest, on fallen corticated piece of wood, leg. E. Yurchenko, 20 Jul 2019, EYu 190720-11 (CFMR).

Xylodon yunnanensis and Hyphodontia yunnanensis

The BLAST search and the reconstruction of phylogeny (Fig. 1) demonstrated that the taxa called Xylodon yunnanensis (with holotype LWZ 20180920-12a (HMAS)) and Hyphodontia yunnanensis (with holotype SWFC 6804) belong to the same species. This is also apparent after comparison of the protologues of X. yunnanensis (Wang et al. 2021) and H. yunnanensis (Boonmee et al. 2021): the cystidial elements, hyphae and spores in these fungi were described as slightly different at best. Both holotypes originate from the same geographic area (Yunnan Province, Chuxiong, Zixi (Zixishan) Forest Park), and were collected in the same year (2018). Because of the priority of publishing date, 12 June 2021 for X. yunnanesis against 7 December 2021 for H. yunnanensis, and taking into account the incorrect placement of the material in Hyphodontia, we propose here the single correct name for the species, X. yunnanensis. In this case, H. yunnanensis is a heterotypic synonym of X. yunnanensis (we do not consider it a homonym because of the different generic epithet).

Xylodon yunnanensis Xue W. Wang & L.W. Zhou, in Wang, May, Liu & Zhou, Journal of Fungi 7, 478: 67 (2021)

= Hyphodontia yunnanensis C.L. Zhao & Y.C. Dai, in Boonmee et al., Fungal Diversity 111: 275 (2021).

Xylodon daweishanensis as insufficiently known taxon

Recently a new species, Xylodon daweishanensis C.L. Zhao, was described (Guan et al. 2023), which apparently belongs in our phylogeny to X. hyphodontinus s. l. (Figs. 2, 4). This new species is based on five specimens collected from a single locality in Yunnan, China, and the only difference from X. hyphodontinus, noted by the authors, is smaller spore size, 3–4 × 2.5–3.5(–4) μm. Our specimen MSK-F 7397 from Taiwan belong to the same subclade as X. daweishanensis, but it has slightly bigger spores, 3.5‒4.5 × 3.5‒4(‒4.5) μm. The specimens from other phylogenetically distinct subclades of X. hyphodontinus have spores of the same size range as MSK-F 7397, except LIP GG-MAR12-238. The latter possesses spores 3.8‒5.4 μm in diameter (G. Gruhn, pers. comm.). Since sequence data from additional genome loci are unavailable for X. daweishanensis and X. hyphodontinus, we place X. daweishanensis amongst insufficiently known taxa.

Discussion

Xylodon lanatus species complex

We have revised here the taxonomy of the X. lanatus species complex, which contains species possessing clusters of projecting, encrusted hyphae or hyphoid cystidia. In light of new sequences, this strongly supported clade can be divided into six separate phylospecies (Figs. 2, 3). Two of them, X. afromontanus and X. mantiqueirensis, are geographically and morphologically distinct from X. lanatus s. str., though the morphological differences are not especially pronounced. To clarify the phylogenetic position of X. lanatus, and to clarify its morphological differences from other components of the X. lanatus complex, we assigned an epitype to X. lanatus s. str., following the recommendations for epitypification (Hyde and Zhang 2008).

Earlier, X. lanatus s. str. was known from the mainland part of the USA only (Riebesehl et al. 2019). The present study expands the range of this species to Puerto Rico and Ecuador. Thus, the range of X. lanatus under the current concept covers temperate coniferous forests (southeast of the USA) and subtropical and tropical moist broadleaf forests (Puerto Rico and Ecuador; Olson et al. 2001), which is not a very common event amongst fungi. We should note, however, that specimens from Puerto Rico and Ecuador form a separate cluster (PP = 1) within the X. lanatus clade (Figs. 2, 3). We do not exclude that after adding several genetic loci in phylogenetic reconstruction, these specimens can be classified as a separate species. Thus, we based the morphological description of X. lanatus above on specimens from temperate localities only.

Our data expanded the known natural range of X. echinatus to the western part of Sunda Archipelago. Earlier the species was known from further north: the protologue of Hyphodontia echinata was based on three specimens from Taiwan and one specimen from Yunnan, China (Yurchenko et al. 2013).

Xylodon hyphodontinus species complex

Our ITS phylogeny suggests that specimens identified as X. hyphodontinus (Fig. 2) may belong to five phylospecies, based on branch length and branch support. Three of this phylospecies are geographically defined: the first one from mainland China and Taiwan, the second from Kenya, and the third from Panama. However, we observed no significant morphological differences amongst these phylospecies, as well as in our previous study (Riebesehl et al. 2019). There are, for example, less encrusted bunches of cystidia in BLS M-5236 in contrast to LIP GG-MAR15-127 and LIP GG-MAR12-238, but this can be explained as non-hereditary variation. In this case, we observe the phenomenon when microevolution rate, reflected in ITS and 28S sequence changes, is higher than morphological differentiation.

With this broad concept X. hyphodontinus has a pantropical distribution: we document here the first finds in Central America (Panama) and Taiwan, and confirmed the occurrence of the species in Ecuador and Cameroon (see list of studied specimens).

Specimens examined for species not presented in the Taxonomy section

Xylodon echinatus – Taiwan. Chiayi County, Alishan Hsiang, Nanhsi Forest Road, coll. S.H. Wu, J.Y. Teng, 8 Dec 1994, Wu 9412-34 (TNM F24751, holotype). Indonesia. Java Island, Jawa Tengah (Central Java) Province, Karanganyar, Mt. Lawu, Cemoro Kandang peak trail, about 2270 m a.s.l., secondary (after fire) Acacia forest, on naked wood of man-made Acacia cf. decurrens Willd. stump, leg. O. Miettinen, 22 May 2014, OM 18328 (H 7200350). Malaysia. Borneo Island, Sabah State, near Kota Kinabalu city, on dead corticated wood, leg. U. Frieling, Oct 2017 (KAS-JR31; dupl. in BLS); Sabah State, on dead hardwood, leg. O. Miettinen, 20 Jun 2013, OM 16459 (H 7200689; dupl. SNP 35201).

Xylodon hyphodontinus – Côte d’Ivoire. Forest of Téké north of Abidjan, on cut wood, leg. G. Gilles, 7 Jul 1974, 248 (LY 7377; holotype of Pteridomyces sphaericosporus). Cameroon. South Province, near Akok, lowland rainforest reserve, coll. M. Núñez, L. Ryvarden, Dec 1991, No. 31192/LR 7725 (O-F-907725; dupl. H 7004978). Ecuador. Orellana Province, the vicinity of Puerto Francisco de Orellana, 0.4861°S, 76.9500°W, 260 m a.s.l., Amazonian rainforest, on dead rachis of Musa sp. leaf, leg. E. Yurchenko, 20 Jul 2019, EYu 190720-68 (BLS M-5236). Panama. Chiriquí Province, Bajo Mono NW of Boquete, southern slopes of Cordillera de Talamanca, 8.8431°N, 82.4750°W, about 1900 m a.s.l., evergreen mountain rainforest, on dead wooden stem, leg. E. Yurchenko, 28 Jul 2019, EYu 190728-2 (MSK-F 11103); ibid., on fallen bush stem, leg. E. Yurchenko, 28 Jul 2019, EYu 190728-9 (BLS M-5237). Taiwan. Taipei County, Wulai, Neidong Natural Forest Recreation Area, 24.8333°N, 121.5333°E, 360 m a.s.l., broadleaf montane subtropical forest, on base of dead small stump of angiosperm tree or bush and partly on soil particles, leg. E. Yurchenko, 23 Jun 2011, EYu 110623-23b (MSK-F 7397; dupl. in BLS).

Xylodon pseudolanatus ‒ USA. Tennessee, Sevier, Little River, Jakes Creek Trail, leg. H.H. Burdsall, Jr., 9 Jul 1970 (CFMR HHB-4305); Virginia, Giles Co., Cascades parking lot, leg. H.H. Burdsall, Jr., 2 Aug 1979 (CFMR HHB-10703-Sp); North Carolina, Wake County, W.B. Umstead State Park, middle-aged, lightly burned Pinus-Acer forest, on dead wood of uprooted tree of Acer (decay stage 2; 12 cm diam.), leg. O. Miettinen, 13 Nov 2013, OM 17556.2 (H 7200690).