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Additions to the taxonomy of Lagarobasidium and Xylodon (Hymenochaetales, Basidiomycota)
expand article infoIlya Viner§, Viacheslav Spirin§|, Lucie Zíbarová, Karl-Henrik Larsson|
‡ Lomonosov State University, Moscow, Russia
§ University of Helsinki, Helsinki, Finland
| University of Oslo, Oslo, Norway
¶ Unaffiliated, Ústí nad Labem, Czech Republic
Open Access

Abstract

Lagarobasidium is a small genus of wood-decaying basidiomycetes in the order Hymenochaetales. Molecular phylogenetic analyses have either supported Lagarobasidium as a distinct taxon or indicated that it should be subsumed under Xylodon, a genus that covers the majority of species formerly placed in Hyphodontia. We used sequences from the ITS and nuclear LSU regions to infer the phylogenetic position of the type species L. detriticum. Analyses confirm Lagarobasidium as a synonym of Xylodon. Molecular and morphological information show that the traditional concept of L. detriticum covers at least two species, Xylodon detriticus from Europe and X. pruinosus with known distribution in Europe and North America. Three species currently placed in Lagarobasidium are transferred to Xylodon, viz. X. magnificus, X. pumilius and X. rickii. Three new Xylodon species are described and illustrated, X. ussuriensis and X. crystalliger from East Asia and X. attenuatus from the Pacific Northwest America. The identity of X. nongravis, described from Sri Lanka, is discussed.

Keywords

Agaricomycetes, Hyphodontia, ITS, LSU, phylogeny

Introduction

The genus Lagarobasidium was introduced by Jülich (1974) for three corticioid species, L. cymosum (D.P.Rogers & H.S.Jacks.) Jülich, L. nikolajevae (Parmasto) Jülich and L. pruinosum (Bres.) Jülich (the generic type). These species possess prominent, thin- or slightly thick-walled cystidia, suburniform tetrasporic basidia and thick-walled basidiospores. Eriksson and Ryvarden (1976) concluded that L. pruinosum is a later synonym of Peniophora detritica Bourdot (Bourdot 1910), which prompted Jülich (1979) to move P. detritica to Lagarobasidium. At present, L. detriticum is accepted in a wide sense, with Hyphodontia magnacystidiata Lindsey & Gilb., H. nikolajevae Parmasto and Odontia pruinosa Bres. as synonyms (http://www.mycobank.org [accessed 07 May 2018]).

Controversies over the taxonomic position of Peniophora detritica emerged during the last decades. In modern morphology-based systems, it was first attributed to Hyphodontia J. Erikss., mainly due to hyphal characters and the shape of basidia (Eriksson 1958, Langer 1994). A second solution was introduced by Eriksson and Ryvarden (1976) who stressed the shape of cystidia and the thick-walled cyanophilous basidiospores and placed the species in Hypochnicium. The third option and the one chosen by Jülich (1974), was to place P. detritica in a genus of its own (Jülich 1974, 1979, Hjortstam and Ryvarden 2009).

Larsson et al. (2006) used the nrLSU and 5.8S genes for a phylogenetic analysis of Hymenochaetales and recovered Peniophora detritica nested in a fairly well-supported clade that also included several species usually classified in Hyphodontia. This result supported the original opinion on relationships introduced by Eriksson (1958) but also showed that Hyphodontia sensu Eriksson was polyphyletic. The clade with Peniophora detritica. recovered by Larsson et al. (2006), was later identified as Xylodon, type species X. quercinus, a genus that now covers the majority of species earlier referred to Hyphodontia (Hjortstam and Ryvarden 2009). On the other hand, Dueñas et al. (2009) studied sequences from the ITS region and concluded that molecular information supported recognition of the separate genus Lagarobasidium. These same ITS sequences have been used by several subsequent researchers, who therefore maintained Lagarobasidium separate from Hyphodontia sensu lato (Yurchenko and Wu 2014, Riebesehl et al. 2015, Chen et al. 2016, Chen et al. 2017, Kan et al. 2017, Riebesehl and Langer 2017, Yurchenko et al. 2017, Chen et al. 2018).

In the present study, we revise the Lagarobasidium detriticum complex based on morphological and molecular methods. We propose to consider Lagarobasidium as a later synonym of Xylodon and to restore Odontia pruinosa as an independent species. In addition, we describe three new Xylodon species and make five new combinations.

Materials and methods

Morphological methods

Type material and specimens from herbaria H, S, O, GB, BPI, TAAM and BAFC were studied. Herbarium abbreviations are given according to Index Herbariorum (Thiers). Microscopic methods are described in Miettinen et al. (2006). All measurements were made in Cotton Blue (CB, Merck 1275) with phase contrast illumination (1250×). The following abbreviations are used in microscopic descriptions: L – mean spore length; W – mean spore width; Q – mean L/W ratio; n – number of spores (hyphae, basidia) measured per number of specimens. We excluded 5% of measurements from each end of the range representing variation of basidiospores and cystidia. Excluded extreme values are given in parentheses when they differ substantially from the lower or higher 95% percentile.

DNA extraction and sequencing

For DNA extraction we used either the standard CTAB protocol (Griffith and Shaw 1998) or DNeasy Plant Mini kit (Qiagen, Hilden, Germany). Primers ITS1F (Gardes and Bruns 1993), ITS4 (White et al. 1990) and LR21 (Hopple and Vilgalys 1999) were used to amplify the internal transcribed spacers 1 and 2 and the 5.8S gene. LR0R, LR5 (Moncalvo et al. 2002) and LR7 (Hopple and Vilgalys 1999) were used to amplify 28S large ribosomal subunit. Polymerase chain reaction (PCR) products were purified with the Cleanup Standard kit (Evrogen Ltd, Moscow, Russia) or QIAquick PCR purification kit (Qiagen, Hilden, Germany). Sequencing reactions were performed either by the Evrogen company (Moscow, Russia) following the BigDye terminator protocol (ABI Prism) on an Applied Biosystems 3730 xl automatic sequencer (Applied Biosystems, CA, USA) with primers ITS1F and ITS4 or with an external service provided by Macrogen (South Korea) using primers ITS1, ITS4, CTB6 (http://plantbio.berkeley.edu/~bruns/), LR5 and LR3R (Hopple and Vilgalys 1999).

Phylogenetic analyses

DNA sequences were edited in Geneious (Biomatters Ltd, Auckland, New Zealand) or in Sequencher 5.2.4 (Gene Codes Co., Ann Arbor, MI, USA) and deposited in GenBank (Table 1). We compiled two sequence datasets. The first one contains full ITS sequences from 83 specimens. The second dataset includes ITS and nLSU sequences from 24 specimens and is a subset of the taxa in the ITS-only dataset. In both datasets, Hastodontia hastata (Litsch.) Hjortstam & Ryvarden (Hymenochaetales) was included as outgroup (Larsson et al. 2006). We generated 13 ITS and 6 nLSU sequences for this study; other sequences used in the analyses were downloaded from GenBank (Benson et al. 2018) or UNITE (Kõljalg et al. 2013) (Table 1). Alignments were calculated through MAFFT 7.407 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 (http://purl.org/phylo/treebase/phylows/study/TB2:S23057).

Specimens and GenBank and UNITE accession numbers for DNA sequences used in this study.

Species Specimen voucher GenBank or UNITE accession numbers for ITS GenBank or UNITE accession numbers for LSU Reference
Hastodontia hastata (Litsch.) Hjortstam & Ryvarden Larsson 14646 MH638232 MH638232 this study
Lyomyces allantosporus Riebesehl, Yurchenko & E. Langer FR-0249548, Holotype KY800397 KY795963 Yurchenko et al. (2017)
Lyomyces crustosus (Pers.) P. Karst. Larsson 11731 DQ873614 DQ873614 Larsson et al. (2006)
Lyomyces erastii (Saaren. & Kotir.) Hjortstam & Ryvarden MA-Fungi 34,336 JX857800 Yurchenko et al. (2017)
Lyomyces griseliniae (G. Cunn.) Riebesehl & E. Langer Larsson 12971 DQ873651 Larsson et al. (2006)
Lyomyces mascarensis Riebesehl, Yurchenko & E. Langer KAS-GEL4833, Holotype KY800399 KY795964 Yurchenko et al. (2017)
Lyomyces microfasciculatus (Yurchenko & Sheng H. Wu) Riebesehl & E. Langer TNM F24757, Holotype JN129976 Yurchenko and Wu (2014)
Lyomyces organensis Yurchenko & Riebesehl MSK7247, Holotype KY800403 KY795967 Yurchenko et al. (2017)
Lyomyces orientalis Riebesehl, Yurchenko & E. Langer KAS-GEL3400 DQ340326 DQ340353 Yurchenko et al. (2017)
Lyomyces pruni (Lasch) Riebesehl & E. Langer Ryberg 021018 DQ873624 DQ873625 Larsson et al. (2006)
Lyomyces sambuci (Pers.) P. Karst. KAS-GEL2414 KY800398 Yurchenko et al. (2017)
KAS-JR7 KY800402 KY795966 Yurchenko et al. (2017)
Lyomyces vietnamensis (Yurchenko & Sheng H. Wu) Riebesehl & E. Langer TNM F973, Holotype JX175044 Yurchenko and Wu (2014)
Palifer verecundus (G. Cunn.) Stalpers & P.K. Buchanan Larsson 12261 DQ873642 Larsson et al. (2006)
Xylodon apacheriensis (Gilb. & Canf.) Hjortstam & Ryvarden Canfield 180, Holotype KY081800 Riebesehl and Langer (2017)
Xylodon asperus (Fr.) Hjortstam & Ryvarden H6013167 UDB031926 Unpublished
KG Nilsson s. n. DQ873606 DQ873607 Larsson et al. (2006)
UC2023169 KP814365 Riebesehl and Langer (2017)
Xylodon astrocystidiatus (Yurchenko & Sheng H. Wu) Riebesehl, Yurchenko & E. Langer Wu 9211-71 JN129972 JN129973 Yurchenko and Wu (2014)
Xylodon attenuatus Spirin & Viner Spirin 8775, Holotype MH324476 this study
Xylodon borealis (Kotir. & Saaren.) Hjortstam & Ryvarden Spirin 9416 MH317760 MH638259 this study
TU115575 UDB016473 Unpublished
UC2022850 KP814307 Riebesehl and Langer (2017)
KUN2352 MH307753 MH638263 this study
TU115495 UDB016350 Unpublished
TU124171 UDB028164 Unpublished
Xylodon bubalinus (Min Wang, Yuan Y. Chen & B.K. Cui) C.C. Chen & Sheng H. Wu Cui 12887 KY290982 Wang and Chen (2017)
Xylodon chinensis (C.C. Chen & Sheng H. Wu) C.C. Chen & Sheng H. Wu Wu 1307-42 KX857802 Chen et al. (2017)
Wu 1407-105, Holotype KX857804 Chen et al. (2017)
Xylodon crystalliger Viner KUN2312, Holotype MH324477 this study
Xylodon detriticus (Bourdot) Viner & Spirin Zíbarová 30.10.17 MH320793 MH651372 this study
Zíbarová 26.05.17 MH320794 MH638264 this study
Xylodon flaviporus (Berk. & M.A. Curtis ex Cooke) Riebesehl & E. Langer ICMP13836 AF145585 Paulus et al. (2000)
Xylodon hastifer (Hjortstam & Ryvarden) Hjortstam & Ryvarden Ryvarden 19767, Holotype KY081801 Riebesehl and Langer (2017)
Xylodon heterocystidiatus (H.X. Xiong, Y.C. Dai & Sheng H. Wu) Riebesehl, Yurchenko & E. Langer Wu 9209-27 JX175045 Yurchenko and Wu (2014)
Xylodon lenis Hjortstam & Ryvarden Wu 0808-32 JX175043 KX857820 Yurchenko and Wu (2014)
Wu 890714-3, Holotype KY081802 Riebesehl and Langer (2017)
Xylodon mollissimus (L.W. Zhou) C.C. Chen & Sheng H. Wu LWZ20160318-3, Holotype KY007517 Kan et al. (2017)
Xylodon nespori (Bres.) Hjortstam & Ryvarden B Nordén 030915 DQ873622 Larsson et al. (2006)
GEL3158 DQ340310 DQ340346 Riebesehl and Langer (2017)
GEL3290 DQ340309 Unpublished
GEL3302 DQ340308 Unpublished
GEL3309 DQ340307 DQ340345 Yurchenko and Wu (2014)
Xylodon niemelaei (Sheng H. Wu) Hjortstam & Ryvarden GC 1508-146 KX857798 Chen et al. (2017)
GEL4998 EU583422 DQ340348 Riebesehl and Langer (2017)
Wu 1010-62 KX857799 Chen et al. (2017)
Xylodon nongravis (Lloyd) Spirin & Viner CHWC1506-2 KX857800 Chen et al. (2017)
Dai 11686 KT989968 Chen et al. (2017)
GC1412-22 KX857801 Chen et al. (2017)
Spirin 5763 MH324469 MH656724 this study
Xylodon nothofagi (G. Cunn.) Hjortstam & Ryvarden PDD:91630 GQ411524 Fukami et al. (2010)
Xylodon ovisporus (Corner) Riebesehl & E. Langer ICMP13837 AF145587 Paulus et al. (2000)
KUC20130725-29 KJ668513 KJ668365 Jang et al. (2016)
Wu 0809-76 KX857803 Chen et al. (2017)
Xylodon paradoxus (Schrad.) Chevall. FCUG 1517 AF145572 Paulus et al. (2000)
FCUG 2425 AF145571 Paulus et al. (2000)
Miettinen 7978 FN907912 FN907912 Miettinen and Larsson (2011)
Xylodon pruinosus (Bres.) Spirin & Viner Larsson 14653 UDB024816 Unpublished
Spirin 2877 MH332700 this study
UC2023108 KP814412 Rosenthal et al. (2017)
Xylodon pseudotropicus (C.L. Zhao, B.K. Cui & Y.C. Dai) Riebesehl, Yurchenko & E. Langer Dai 10768, Holotype KF917543 Zhao et al. (2014)
Xylodon quercinus (Pers.) Gray Kotiranta 27060 MH320792 this study
Larsson 11076 KT361633 AY586678 Ariyawansa et al. (2015)
Miettinen 15050,1 KT361632 Ariyawansa et al. (2015)
Spirin 8565 MH316007 this study
Spirin 8840 MH320791 this study
Xylodon raduloides (Pers.) Riebesehl & E. Langer Dai 12631 KT203307 KT203328 Moncalvo et al. (2002)
ICMP13833 AF145580 Paulus et al. (2000)
Xylodon ramicida Spirin & Miettinen Spirin 7664, Holotype KT361634 Ariyawansa et al. (2015)
Xylodon reticulatus (C.C. Chen & Sheng H. Wu) C.C. Chen & Sheng H. Wu GC 1512-1 KX857808 Chen et al. (2017)
Wu 1109-178, Holotype KX857805 Chen et al. (2017)
Xylodon rhizomorphus (C.L. Zhao, B.K. Cui & Y.C. Dai) Riebesehl, Yurchenko & E. Langer Dai 12354 KF917544 Zhao et al. (2014)
Xylodon rimosissimus (Peck) Hjortstam & Ryvarden CFMR:DLL2011-081 KJ140600 Brazee et al. (2014)
Ryberg 021031 DQ873627 DQ873628 Larsson et al. (2006)
UC2022842 KP814311 Rosenthal et al. (2017)
UC2023109 KP814414 Rosenthal et al. (2017)
UC2023147 KP814193 Rosenthal et al. (2017)
UC2023148 KP814194 Rosenthal et al. (2017)
Xylodon spathulatus (Schrad.) Kuntze GEL2690 KY081803 Riebesehl and Langer (2017)
Larsson 7085 KY081804 Riebesehl and Langer (2017)
Xylodon subtropicus (C.C. Chen & Sheng H. Wu) C.C. Chen & Sheng H. Wu Wu 1508-2 KX857806 Chen et al. (2017)
Wu 9806-105, Holotype KX857807 Chen et al. (2017)
Xylodon ussuriensis Viner KUN1989, Holotype MH324468 this study

We inferred phylogenetic trees with maximum likelihood (ML), maximum parsimony (MP) and Bayesian Inference (BI) but provide only the last one since all trees show congruity of the phylogenetic signal. Substitution models were determined with the aid of TOPALi 2.5 (Milne et al. 2008) based on Bayesian information criterion (BIC). GTR + G (nst = 6, rates = gamma) were the best-fit models for the whole ITS region in the ITS dataset as well as in the ITS + nrLSU dataset. SYM + G (nst = 6, rates = gamma, statefreqpr = fixed(equal)) was the best-fit model for the nrLSU region in the ITS + nrLSU 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. Following models suggested by TOPALi 2.5, we preferred to use the GTR model with gamma correction (GTRGAMMA) in ML analysis for both datasets. The bootstrapping was performed using the ‘Rapid bootstrapping’ algorithm with the number of bootstrap replicates set as 1000.

Maximum parsimony (MP) analysis was performed using MEGA 7 (Kumar et al. 2016). We used the Subtree-Pruning-Regrafting (SPR) algorithm using all sites. The number of bootstrap replicates was set as 1000.

Specimens examined (sequenced specimens are marked by an asterisk)

Xylodon attenuatus. USA. Washington: Clallam Co., La Push, Pseudotsuga menziesii, 8 Oct 2014, Spirin 8286a (H), Sol Duc, Tsuga heterophylla, 6 Oct 2014, Spirin 8133 (H); Jefferson Co., Hoh River, Acer macrophyllum, 20 Oct 2014, Spirin 8775* (H, holotype), Tsuga heterophylla, 20 Oct 2014, Spirin 8779 (H); Pend Oreille Co., Gypsy Meadows, Picea engelmannii, 17 Oct 2014, Spirin 8694* (H). Canada. British Columbia: Fraser-Fort George Reg. Dist., Mt. Robson Provincial Park, Picea sp., 25 Jul 2015, Spirin 8900a (H).

X. borealis. Russia. Nizhny Novgorod Reg.: Lukoyanov Dist., Panzelka, Quercus robur (very rotten log), 17 Aug 2015, Spirin 9416* (H).

X. brevisetus. Russia. Moscow: Losiny Ostrov Nat. Park, log of Pinus sylvestris, 1 Oct 2016, A.Nechaev KUN2352* (H).

X. crystalliger. Russia. Primorie: Khasan Dist., Kedrovaya Pad Nat. Res., on angiosperm wood, 25 Jul 2016, I.Viner KUN 2312* (H, holotype); ibidem 29 Jul 2017, F.Bortnicov, KUN 3347 (H).

X. detriticus. Czech Republic. Karlovarský kraj: Sokolov, Antonín mine spoil, on Phragmites australis, 26 May 2017, L.Zíbarová (H*); Liberecký kraj: Liberec, Uhelná, on Calamagrostis epigejos, 30 Oct 2017, L.Zíbarová (H*). France. Auvergne: Allier, St. Priest, on fern, 1 Sep 1909, H.Bourdot 7226 (S F204453, lectotype of Peniophora detritica). Italy. Lazio: Circeo Nat. Park, on Pinus pinea bark, 23 Oct 1984, K.H.Larsson 5496 (GB); ibidem, on fallen leaves, 24 Oct 1984, K.H.Larsson 5622 (GB); ibidem, on ferns, 24 Oct 1984, K.H.Larsson 5627 (GB).

X. magnificus. Argentina. Tierra del Fuego: Ushuaia, Estancia Moat, on Drimys winteri, 21 Mar 1998, A.Greslebin 1387 (GB, paratype duplicate).

X. nongravis. Russia. Khabarovsk Reg.: Khabarovsk Dist., Ulun, on Salix schwerinii, 25 Aug 2012, V.Spirin 5615 (H); ibidem, on Corylus mandshurica, 28 Aug 2012, V.Spirin 5763* (H); Primorie Reg.: Krasnoarmeiskii Dist., Melnichnoe, on Corylus mandshurica, 21–23 Aug 2013, V.Spirin 6218, 6260, 6281 (H). Sri Lanka. Peradeniya, on rotten branch, T.Petch (BPI US0305211, holotype of Polyporus nongravis).

X. pruinosus. Estonia. Ida-Virumaa: Kohtla-Järve, Pärnassaare, on Betula pubescens, 1 Oct 1958, E.Parmasto (TAAM, holotype of Hyphodontia nikolajevae). Finland. Helsinki: Veräjämäki, on Salix caprea, 4 Sep 2011, O.Miettinen 14651.4 (H). Germany. Nordrhein-Westfalen, on Betula sp., W.Brinkmann (S F204462, isolectotype of Odontia pruinosa). Norway. Akershus: Frogn, decaying deciduous wood, 3 Oct 2010, K.H.Larsson 14653* (O). Russia. Nizhny Novgorod Reg.: Bogorodsk Dist., Krastelikha, on Quercus robur, 11 Aug 2009, V.Spirin 2877* (H); Lukoyanov Dist., Panzelka, on Populus tremula, 19 Aug 2015, V.Spirin 9581 (H); Razino, on Quercus robur, 16 Aug 2015, V.Spirin 9350 (H); Srednii, on Tilia cordata, 18 Aug 2006, V.Spirin 2601 (H); Pavlovo Dist., Chudinovo, on Populus tremula, 3 Oct 2015, V.Spirin 9994 (H); Sverdlovsk Reg.: Nizhnisereginskii Dist., Olenii Ruchii Nat. Park, on Populus tremula, 19–20 Aug 2002, H.Kotiranta 19684b, 19687, 19715a (H). USA. New York: Franklin County, Paul Smith’s, on Populus tremuloides, 12 Sep 1965, R.L.Gilbertson 5481 (GB, isotype of Hyphodontia magnacystidiata).

X. pumilius. Argentina. Chubut: Río Senguer, Lago La Plata, on Nothofagus pumilio, 26–28 Mar 1996, A.Greslebin 701 (GB, paratype duplicate).

X. quercinus. Canada. Alberta: Yellowhead Co., William A. Switzer Prov. Park, on Populus tremuloides, 24 Jul 2015, V.Spirin 8840* (H). Finland. Uusimaa: Helsinki, Veräjänmäki, on angiosperm wood, 12 Apr 2008, O.Miettinen 12409* (H). Russia. Chukotka: Anadyr, on Alnus fruticosa, 19 Sep 2009, H.Kotiranta 27060* (H). USA. Washington: Pend Oreille Co., Slate Creek, on Corylus cornuta, 15 Oct 2014. V.Spirin 8565* (H).

X. rickii. Brazil. Rio Grande do Sul: S. Salvador, 5 Apr 1944, J.Rick 20847 (O, isotype of Odontia polycystidifera).

X. ussuriensis. Russia. Primorie: Khasan Dist., Kedrovaya Pad Nat. Res., angiosperm wood, 24 Jul 2016, I.Viner KUN 1989* (H, holotype of Xylodon ussuriensis), I.Viner KUN 2103, 2186.

Results

For both datasets, the Bayesian inference returned trees with two main clades (Figures 1, 2); the largest clade is well-supported and corresponds to Xylodon (pp 1.0), while the other clade is unsupported and includes Lyomyces, the Hyphodontia crustosa group, H. pruni and Rogersella griseliniae (pp 0.89). Basal relationships within Xylodon are not resolved. Peniophora detritica and its allied species are nested within Xylodon and form a well-supported subclade together with X. borealis and X. brevisetus (Figures 1, 2). Maximum likelihood and maximum parsimony returned similar topologies and relevant support values from these analyses are indicated on nodes in Figures 1, 2.

Figure 1. 

Phylogenetic relationships of Xylodon inferred from ITS sequences using Bayesian analysis. A 50% majority rule consensus phylogram. Bayesian posterior probabilities, ML bootstrap and MP bootstrap values are shown on nodes; branch lengths reflect estimated number of changes per site.

Figure 2. 

Phylogenetic relationships of Xylodon inferred from ITS and LSU sequences using Bayesian analysis. A 50% majority rule consensus phylogram. Bayesian posterior probabilities, ML bootstrap and MP bootstrap values are shown on nodes; branch lengths reflect estimated number of changes per site.

In the ITS-only tree, three terminal branches represent new species that are described below. Xylodon attenuatus occurs as a sister taxon to X. rimosissimus; X. crystalliger forms a subclade with X. astrocystidiatus, X. paradoxus and X. heterocystidiatus; and X. ussuriensis is the sister taxon to X. detriticus and X. pruinosus (Figure 1).

The results allow us to introduce new species and new combinations as follows.

Xylodon attenuatus Spirin & Viner, sp. nov.

MycoBank No: MB825367
Figure 3

Type

USA. Washington: Jefferson Co., Hoh River, on Acer macrophyllum, 20 Oct 2014, V.Spirin 8775 (H) – ITS sequence, GenBank MH324476.

Etymology

Attenuatus (lat., adj.) – exhausted, thin.

Description

Basidiocarp effused, up to 5 cm in widest dimension. Sterile margin white, up to 1 mm wide. Hymenial surface cream-coloured, grandinioid to odontoid; projections rather regularly arranged, from 80 µm to 200 μm high, 70–90 μm broad at base, 6–8(–9) per mm. Hyphal structure monomitic, hyphae clamped, cyanophilous. Subicular hyphae densely interwoven, thin-walled, (2–)2.4–4.6 μm in diam. (n=60/6), often short-celled, the outline of these hyphae often irregular. Tramal hyphae subparallel, thin-walled, in subhymenium densely arranged, sometimes short-celled, 2.4–3.6 μm in diam. (n=62/6). Large stellate crystals 10–13.3 μm in diam. present in subiculum and trama. Cystidia originating from subhymenium, of two types: a) subcapitate or capitate cystidia, (12–)13.5–25.1(–37)×(2.7–)3.3–5(–5.5) μm (n=80/6), b) hyphoid cystidia, (14–)16–38.3(–40.8)×2.8–4.5 (n=51/6), sometimes with crystalline cap on the top; some cystidia with granular contents in CB. Basidia suburniform, 4-spored, (12.2–)14–22(–25)×(3–)3.3–4.6(–5) μm (n=61/2), slightly thick-walled at the base. Basidiospores thin-walled, ellipsoid, (3.7–)4.1–5.5(–6)×(3–)3.4–4.5(–4.9) μm (n=180/6), L=4.85, W=3.98, Q=1.22, slightly cyanophilous.

Figure 3. 

Xylodon attenuatus (holotype): a section through an aculeus b basidia c subhymenial short-celled hyphae d cystidia e basidiospores.

Distribution and ecology

North-western USA (Washington), on angiosperm and gymnosperm wood (fallen decorticated logs).

Remarks

Xylodon attenuatus bears morphological similarity to X. borealis, although densely arranged hyphae, star-like crystals and a regular presence of cystidia with granular contents make it easily recognisable. The crystalline caps on hyphoid cystidia are other characteristics useful for the identification of X. attenuatus.

Xylodon crystalliger Viner, sp. nov.

MycoBank No: MB825368
Figure 4

Type

RUSSIA. Primorie: Khasan Dist., Kedrovaya Pad Nat. Res., on angiosperm wood, 25 Jul 2016, I.Viner KUN 2312 (H) – ITS sequence, GenBank MH324477.

Etymology

Crystalliger (lat., adj.) – bearing crystals.

Description

Basidiocarp effused, soft membranaceous, up to 6 cm in widest dimension. Sterile margin poorly defined, up to 0.3 mm wide. Hymenial surface white, minutely odontioid, i.e. covered by small peg-like hyphal projections up to 60–100 μm high, 60–75 μm broad at base, 10–15 per mm, with flattened fimbriate apices. Surface between projections porulose-reticulate. Hyphal structure monomitic, hyphae clamped, faintly cyanophilous. Subicular hyphae densely interwoven, often with thickened walls, 3.2–4.4 μm in diam. (n=20/2), smooth or sparsely encrusted. Tramal hyphae subparallel, thin- to clearly thick-walled, sparsely encrusted, subhymenial hyphae densely arranged, sometimes short-celled, 2.5–3.2 μm in diam. (n=20/2), sparsely encrusted. Hyphal ends at the top of projections often strongly encrusted. Cystidia of two types: a) sparsely encrusted hyphoid cystidia at the top of projections, 21.0–29.0×2.9–4.1(–4.4) μm (n=40/2), b) subcapitate or cylindrical cystidia, of subhymenial origin, rather variable in shape and size, (11.8–)14.1–25.0(–28.0)×(2.6–)2.9–4.6(–4.8) μm (n=40/2), often heavily encrusted and rarely with a stellate crystalline cap 3.5–4.5 μm in diam. Basidia suburniform, 4-spored, 13.4–18.4(–19.0)×4.2–4.7 μm (n=20/2), slightly thick-walled at the base. Basidiospores thin-walled, elliptical, occasionally with an oil-drop, (3.1–)4.2–5.1(–5.9)×(2.4–)3.3–4.2 μm (n=60/2), L=4.66, W=3.71, Q=1.26, slightly cyanophilous.

Figure 4. 

Xylodon crystalliger (holotype): a section through an aculeus b apically encrusted hyphae from aculeal tips c basidiospores d basidia e cystidia f subhymenial hyphae.

Distribution and ecology

East Asia (Russian Far East), on decayed angiosperm logs.

Remarks

The peg-like hymenial projections and cystidia with stellate caps are characteristic for X. crystalliger and make it reminiscent of Xylodon astrocystidiatus (Yurchenko & Sheng H. Wu) Riebesehl, Yurchenko & Langer. The latter species is known from Taiwan and differs from X. crystalliger by having longer basidiospores and presence of constricted and bladder-like hymenial cystidia.

Xylodon detriticus (Bourdot) K.H. Larss., Viner & Spirin, comb. nov.

MycoBank No: MB825366
Figures 5, 6c, 7

Basionym

Peniophora detritica Bourdot, Revue Scientifique du Bourbonnais et du Centre de la France 23: 13. 1910. ≡ Lagarobasidium detriticum (Bourdot) Jülich, Persoonia 10: 334. 1979. Type. France. Auvergne: Allier, St. Priest, fern, 1.IX.1909 Bourdot 7226 (lectotype S! [F204453], designated by Eriksson and Ryvarden 1976: 703).

Description

Basidiocarps effused, up to 5 cm in widest dimension. No differentiated margin. Hymenial surface white, smooth or warted, farinaceous. Hyphal structure monomitic, hyphae clamped, faintly cyanophilous, thin-walled. Subicular hyphae interwoven and frequently branched, (2.2–)3.0–5.9 μm in diam. (n=61/6). Tramal hyphae subparallel, subhymenial hyphae short-celled, (1.5–)1.9–3.5 μm in diam. (n=61/6). Large, rhomboid or stellate crystals abundant in trama and subiculum, 8–10.5 μm in diam. Cystidia of two types: a) large, thin-walled cystidia of subicular or tramal origin, cylindrical or clavate, rarely slightly thick-walled (wall not exceeding 1 μm thick), (30.0–)58.9–110.0(–115.0)×4.1–8.5(–9.6) μm (n=120/6), occasionally bearing 1–2 clamped septa, b) rare astrocystidia of subhymenial origin, with a stellate crystalline cap 10–23×2–3.1 μm, in some specimens difficult to find. Basidia suburniform, 4-spored, (12.2–)13.1–20.0×(3.1–)3.4–5.0 μm (n=61/6), thin-walled. Basidiospores clearly thick-walled, elliptical to broadly elliptical, usually with an oil-drop, (3.3–)4.3–5.7(–6.1)×3.2–4.1(–4.5) μm (n=190/6), L=4.92, W=3.69, Q=1.34, cyanophilous.

Figure 5. 

Cystidial elements of Xylodon detriticus: a Larsson 5496 b Zíbarová 26.V.2017 c Zíbarová 30.X.2017.

Distribution and ecology

. Europe (Czech Republic, France, Italy), on herbaceous remnants, once collected from pine bark at the same spot where it was found on fern remains.

Remarks

Eriksson and Ryvarden (1976) selected Bourdot 7226 (in herb. S) as lectotype. They also treated Hyphodontia nikolajevae and Odontia pruinosa as synonyms. However, the type specimens of H. nikolajevae and O. pruinosa reveal small differences from the type material and other collections of X. detriticus studied by us. The main features of X. detriticus versus the two other taxa are narrower basidiospores (must be observed in cotton blue) and longer, narrower cystidia having no distinct intercalary inflation (Tables 2, 3, Figures 5, 6). Eriksson and Ryvarden (1976) attributed the differences in cystidia morphology between Bourdot’s specimen and types of H. nikolajevae and O. pruinosa to different stages of basidiocarp development. Our investigation indicates that the differences are genetic and species specific. Differences in basidiospore size and shape are detectable in CB but not in KOH, which could explain why they have gone unnoticed in earlier studies.

Figure 6. 

Basidiospores of two Xylodon species in CB: a X. pruinosus (Spirin 9994) b X. pruinosus (isotype of Hyphodontia magnacystidiata) c X. detriticus Zíbarová (26.V.2017).

Hjortstam and Ryvarden (2009) added Hyphodontia magnacystidiata to the synonymy of X. detriticus. This species is, as far as we know, only known from the type, collected on dead wood of Populus in New York, USA (Lindsey and Gilbertson 1977). It has an odontioid basidiocarp and its cystidia are similar to those of X. pruinosus (Table 3, Figures 6, 8). On the other hand, the basidiospore size is very close to X. detriticus (Table 2). In the absence of sequenced material, it is not possible to decide whether this is an independent species or not. Considering that the single specimen was growing on wood and that X. detriticus is not yet found in North America, we prefer to keep H. magnacystidiata as a synonym of X. pruinosus (see below).

Figure 7. 

Basidiocarp of Xylodon detriticus (Zíbarová 26.V.2017). Scale bar: 5 mm.

Figure 8. 

Cystidial elements and basidia of Xylodon pruinosus (isotype of Hyphodontia magnacystidiata).

Spore measurements of five Xylodon species.

Species / specimen L' L W' W Q' Q n
Xylodon attenuatus (3.7) 4.1–5.5 (6) 4.85 (3) 3.4–4.5 (4.9) 3.98 (0.98) 1.06–1.38 (1.46) 1.22 180
Holotype (4.3) 4.4–5.7 (5.8) 4.86 (3) 3.5–4.3 (4.7) 3.84 (1.1) 1.2–1.4 (1.5) 1.27 30
Spirin 8133 (4.4) 4.54–5.3 (5.5) 5.01 (3.2) 3.8–4.6 (4.7) 4.14 (1.06) 1.1–1.33 (1.38) 1.21 30
Spirin 8286 (4.1) 4.14–5.74 (6) 4.98 (3.1) 3.84–4.5 (4.5) 4.11 (1.02) 1.09–1.34 (1.36) 1.21 30
Spirin 8779 (4) 4–5.2 (5.4) 4.67 (3) 3.2–4.3 (4.4) 3.82 (0.98) 1.04–1.38 (1.43) 1.23 30
Spirin 8900a (3.7) 3.95–5.25 (5.6) 4.56 (3.4) 3.4–4.35 (4.9) 3.94 (1.02) 1.02–1.29 (1.37) 1.16 30
Spirin 8964 (4.5) 4.6–5.6 (5.7) 5.02 (3.5) 3.6–4.3 (4.8) 4.04 (1.1) 1.1–1.4 (1.4) 1.25 30
Xylodon crystalliger (3.1) 4.2–5.1 (5.9) 4.66 (2.4) 3.3–4.2 (4.3) 3.71 (1) 1.1–1.4 (1.6) 1.26 60
Holotype (3.1) 4.2–5.1 (5.9) 4.63 (2.4) 3.1–3.8 (3.9) 3.5 (1.2) 1.2–1.5 (1.6) 1.32 30
Bortnicov KUN 3347 (4.2) 4.2–5.3 (5.5) 4.69 (3.3) 3.6–4.2 (4.3) 3.91 (1) 1.1–1.4 (1.4) 1.2 30
Xylodon detriticus (3.3) 4.3–5.7 (6.1) 4.92 (3.1) 3.2–4.1 (4.5) 3.69 (0.7) 1.1–1.6 (1.8) 1.34 190
Lectotype (4.2) 4.3–6 (6.1) 5.07 (3.1) 3.2–4 (4.1) 3.59 (1.2) 1.2–1.6 (1.7) 1.42 39
Larsson 5496 (3.3) 4.2–5.5 (6) 4.87 (3.1) 3.2–4.1 (4.5) 3.61 (0.7) 1.1–1.6 (1.8) 1.36 30
Larsson 5622 (4) 4.2–5.1 (5.5) 4.6 (3.3) 3.4–3.9 (4) 3.63 (1.1) 1.1–1.4 (1.5) 1.27 30
Larsson 5627 (4) 4.2–5 (5.6) 4.69 (3.3) 3.3–4.1 (4.2) 3.73 (1.1) 1.2–1.4 (1.4) 1.26 31
Zibarova 26.V.2017 (4.4) 4.7–5.8 (5.9) 5.26 (3.2) 3.3–4.2 (4.3) 3.83 (1.1) 1.2–1.6 (1.7) 1.38 30
Zibarova 30.X.2017 (4.2) 4.2–5.7 (5.9) 4.99 (3.2) 3.3–4.1 (4.2) 3.78 (1.1) 1.1–1.5 (1.7) 1.32 30
Xylodon pruinosus (4) 4.5–5.9 (7) 5.09 (3.3) 3.7–4.8 (5.7) 4.12 (0.8) 1.1–1.4 (1.5) 1.24 192
Holotype of Hyphodontia nikolajevae (4.6) 4.7–6 (7) 5.26 (3.5) 3.8–5 (5.3) 4.32 (1) 1.1–1.4 (1.4) 1.22 31
Holotype of Odontia pruinosa (4) 4.1–5.7 (5.9) 4.95 (3.5) 3.6–4.5 (4.6) 4.03 (1.1) 1.1–1.4 (1.4) 1.23 40
Spirin 2877 (4.5) 4.7–6.1 (6.3) 5.28 (3.5) 3.8–5 (5.2) 4.21 (1) 1.1–1.4 (1.5) 1.26 30
Spirin 9350 (4.4) 4.7–5.7 (6.2) 5.21 (3.5) 3.8–4.8 (5.7) 4.17 (0.8) 1.1–1.4 (1.5) 1.26 31
Spirin 9581 (4.2) 4.2–5.8 (6.1) 4.99 (3.3) 3.6–4.4 (4.6) 3.98 (1) 1.1–1.4 (1.4) 1.25 30
Spirin 9994 (4.2) 4.6–5.1 (5.3) 4.89 (3.5) 3.6–4.5 (4.6) 4.04 (1.1) 1.1–1.3 (1.4) 1.21 30
Holotype of Hyphodontia magnacystidiata (4) 4.3–5.5 (5.6) 4.92 (3.1) 3.1–4 (4.2) 3.68 (1.1) 1.1–1.6 (1.7) 1.35 30
Xylodon ussuriensis (4.8) 5.1–6 (6.2) 5.48 (3.7) 3.8–4.6 (4.8) 4.21 (1.2) 1.2–1.4 (1.5) 1.3 92
Holotype (4.9) 5.1–5.9 (6.2) 5.48 (3.7) 3.8–4.6 (4.8) 4.22 (1.2) 1.2–1.4 (1.4) 1.3 32
Viner KUN 2103 (4.8) 5–6.1 (6.2) 5.6 (3.8) 3.8–4.7 (4.7) 4.24 (1.2) 1.2–1.4 (1.5) 1.32 30
Viner KUN 2186 (5) 5–5.7 (5.8) 5.37 (3.8) 4–4.5 (4.6) 4.18 (1.2) 1.2–1.4 (1.5) 1.28 30

Measurements of cystidial elements of Xylodon detriticum and X. pruimosus.

Species / specimen L' L W' W n
Xylodon detriticus (30) 58.9–110 (115) 85 (4) 4.1–8.5 (9.6) 6.3 120
Lectotype (67) 69.9–96.7 (110) 83.8 (4) 4–9.1 (9.2) 6.5 20
Larsson 5496 (30) 45.2–108.2 (112) 81.2 (4.1) 4.3–7 (7.2) 5.7 20
Larsson 5622 (30) 45–103 (110) 82.7 (4.1) 4.3–7.5 (8.5) 5.7 20
Larsson 5627 (56) 58.7–104.6 (110) 79.1 (4.4) 4.8–8.9 (9.6) 6.4 20
Zibarova 26.V.2017 (80) 83.8–103.3 (110) 95.1 (4) 5.4–8.1 (8.5) 7.1 20
Zibarova 30.X.2017 (67) 73.7–112.2 (115) 87.7 (4) 5–7.4 (7.5) 6.3 20
Xylodon pruinosus (35) 44–84 (107) 61.9 (4) 4.9–10.9 (12.4) 7.2 146
Holotype of Hyphodontia nikolajevae (41) 43–95 (99) 64 (4) 5–12 (12) 7.7 21
Isolectotype of Odontia pruinosa (43) 45.9–80.4 (107) 64 (4.6) 5.3–10.6 (12.4) 7.3 20
Spirin 2877 (35) 42.6–80 (80) 58.4 (4) 4.8–7.9 (8) 6.2 20
Spirin 9350 (41) 44.8–83.2 (86) 61.8 (4.6) 4.7–10 (10.7) 7.2 20
Spirin 9581 (49) 51.8–84.1 (86) 64.6 (4.9) 5–9 (11) 7.1 20
Spirin 9994 (45) 45.8–75.3 (81) 58.9 (5.3) 5.6–10.2 (10.8) 7.8 20
Isotype of Hyphodontia magnacystidiata (48) 51–95 (104) 75.8 (4.1) 6–12 (14) 8.4 25

Xylodon detriticus grows on ferns and grasses, developing thin farinaceous basidiocarps. The species evidently has a more southern distribution than X. pruinosus. Earlier reports of X. detriticus from woody substrates should be treated with caution and may represent X. pruinosus or as yet undescribed taxa.

Xylodon magnificus (Gresl. & Rajchenb.) K.H. Larss., comb. nov.

MycoBank No: MB827074

Basionym

Hyphodontia magnifica Gresl. & Rajchenb., Mycologia 92: 1160. 2000.

Type

Argentina. Tierra del Fuego: Dpto. Ushuaia, Estancia Moat, on Drimys winteri, 21 Mar 1998, M. Rajchenberg 11370 (holotype: BAFC [50038], by original designation).

For a detailed description and illustration, see Greslebin and Rajchenberg (2000). The authors compared the new species with Xylodon detriticus (as Hyphodontia detritica) and Hypochnicium rickii. Our investigation of authentic material confirms the morphological similarity amongst these three species.

Xylodon nongravis (Lloyd) C.C. Chen & Sheng H. Wu, in Chen et al. 2018: 349

Figure 9

Basionym

Polyporus nongravis Lloyd, Mycol. Writings 6 (61): 891. 1919.

Type

Sri Lanka. Peradeniya, on rotten branch, T.Petch (holotype BPI [305211]).

Wu (2000) re-described and illustrated this poroid species as Hyphodontia nongravis (Lloyd) S.H. Wu. Our specimens collected in the Russian Far East fit well with his description. One of these collections (Spirin 5763) was sequenced and proved to be close to other sequences of H. nongravis available in GenBank. The species undoubtedly belongs to the core Xylodon clade (Figure 1) where it has been combined by Chen et al. (2018). However, the type specimen of Polyporus nongravis possesses small but clear morphological differences from our collections: in particular, wider pores (2–3 per mm in the type, 3–4 per mm in East Asian specimens) and broader tramal hyphae (4–6 μm vs. 3–4.5 μm in diam.), as well as broader, predominantly subglobose basidiospores, 3.9–4.7×3.6–4.2 μm (n=30/1), L=4.27, W=3.97, Q=1.08 (vs ovoid-ellipsoid, 4.0–5.2×3.0–4.1 μm (n=60/2), L=4.74, W=3.46, Q=1.38 in East Asian specimens). An epitype for P. nongravis from the locus classicus is needed to re-introduce this species based on modern methods and to clarify the taxonomic status of X. nongravis sensu East Asia.

Figure 9. 

Basidiocarp of Xylodon nongravis (Spirin 5763). Scale bar: 5 mm.

Xylodon pruinosus (Bres.) Spirin & Viner, comb. nov.

MycoBank No: MB825369
Figures 6 a,b, 8, 10, 11

Basionym

Odontia pruinosa Bres., Annales Mycologici 18 (1–3): 43. 1920. ≡ Lagarobasidium pruinosum (Bres.) Jülich, Persoonia 8: 84. 1974.

Type

Germany. Nordrhein-Westfalen, Lengerich, W.Brinkmann (lectotype L [L 0053271], designated by Jülich 1974: 84).

= Hyphodontia nikolajevae Parmasto, Conspectus Systematis Corticiacearum: 213. 1968. Type: Estonia. Ida-Virumaa, Kohtla-Järve, Pärnassaare, on Betula pubescens, 1 Oct 1958, E.Parmasto (holotype: TAAM [9683], by original designation).

= Hyphodontia magnacystidiata Lindsey & Gilb., Mycotaxon 5: 315. 1977. Type: USA. New York, Franklin County, Paul Smith’s, on Populus tremuloides, 12 Sep 1965, R.L.Gilbertson 5481 (holotype: BPI [266395], by original designation).

Description

Basidiocarps annual, resupinate, up to 5 cm in widest dimension. Margin poorly differentiated, pruinose. Hymenial surface greyish-white or pale cream-coloured, grandinioid to odontoid; projections rather regularly arranged, from 100 µm to 250 µm high, 80–100 μm broad at base, 6–8 per mm. Hyphal structure monomitic, hyphae clamped, faintly cyanophilous, thin-walled. Subicular hyphae interwoven and frequently branched, 2.2–4.7(–6.1) μm in diam. (n=60/6). Tramal hyphae subparallel, subhymenial hyphae short-celled, 2.0–3.5(–3.9) μm in diam. (n=60/6). Stellate crystals abundant in trama, subiculum and subhymenium, 4.4–8.3 μm in diam. Cystidia large, thin-walled, of subicular, tramal or subhymenial origin, clavate to spathuliform, often with an intercalary inflation, sometimes slightly thick-walled (wall not exceeding 1 μm thick), rarely forked, (35.0–)44.0–84.0(–107.0)×(4.0–)4.9–10.9(–12.4) μm (n=121/6), occasionally bearing 1–2 clamped septa. Basidia suburniform, 4-spored, (12.0–)14.0–20.8(–24.0)×3.4–4.2(–5.5) μm (n=60/6), thin-walled. Basidiospores clearly thick-walled, ellipsoid to broadly ellipsoid, usually with an oil-drop, (4.0–)4.5–5.9(–7.0)×(3.3–)3.7–4.8(–5.7) μm (n=192/6), L=5.09, W=4.12, Q=1.24, cyanophilous.

Figure 10. 

Cystidial elements of Xylodon pruinosus: a Spirin 9581 b Spirin 2877 c holotype of Hyphodontia nikolajevae.

Figure 11. 

Basidiocarp of Xylodon pruinosus (Spirin 2877). Scale bar: 5 mm.

Distribution and ecology

Europe (Estonia, Finland, Germany, Norway, Russia – up to Ural Mts.), North America, on medium-decayed wood of angiosperms.

Remarks

. The type specimen of Hyphodontia nikolajevae Parmasto reveals no essential differences from the type and other collections of X. pruinosus studied by us. On average, Xylodon pruinosus has wider basidiospores than X. detriticus (Table 2).

Xylodon pumilius (Gresl. & Rajchenb.) K.H. Larss., comb. nov.

MycoBank No: MB827075

Basionym

Hyphodontia pumilia Gresl. & Rajchenb., Mycologia 92: 1162. 2000.

Type

Argentina. Chubut. Dpto Languiñeo, Lago Engaño, on Nothofagus pumilio, 19 Apr 1996, A.Greslebin 650 (holotype BAFC [50031], by original designation).

For a detailed description and illustration, see Greslebin and Rajchenberg (2000). The presence of both hymenial, capitate cystidia and enclosed, tubular to moniliform cystidia with homogenous contents strongly stained by cotton blue, make this species morphologically reminiscent of Xylodon brevisetus and X. tuberculatus. X. pumilius differs from both by a smooth hymenium and thick-walled basidiospores.

Xylodon rickii (Hjortstam & Ryvarden) K.H. Larss., comb. nov.

MycoBank No: MB827076

Basionym

Hypochnicium rickii Hjortstam & Ryvarden, Mycotaxon 15: 271. 1982. ≡ Odontia polycystidifera Rick, Iheringia, Sér. Bot. 5: 163. 1959. Nom. inval. (Code Art. 40.1).

Type

Brazil. S. Salvador, 5 Apr 1944, Rick 20847 (holotype PACA, by original designation).

For a description, see Hjortstam and Ryvarden (1982). Gorjón (2012) could not verify the presence of large capitate cystidia, similar to those present in X. magnifica and included in the original description by Hjortstam and Ryvarden (1982). We restudied the isotype in herbarium O and can confirm that these large cystidia do exist, which supports a possible position of this species close to X. detriticus and X. pruinosus.

Xylodon ussuriensis Viner, sp. nov.

MycoBank No: MB825356
Figure 12

Type

RUSSIA. Primorie: Khasan Dist., Kedrovaya Pad Nat. Res., on angiosperm wood, 24 Jul 2016, I.Viner KUN 1989* (H) – ITS sequence, GenBank MH324468.

Etymology

Ussuriensis (lat., adj.) – from the river Ussuri in Russian Far East and adjacent China.

Description

Basidiocarps effused, up to 10 cm in longest dimension. Sterile margin white to pale ochraceous, floccose, up to 1 mm wide. Hymenial surface pale ochraceous, grandinioid to odontoid; projections rather regularly arranged, from 100 µm to 250 μm high, 90–110 μm broad at base, 6–8(–9) per mm. Hyphal structure monomitic, hyphae clamped, faintly cyanophilous, thin-walled. Subicular hyphae interwoven, (3.0–)3.4–6.2 μm in diam. (n=30/3). Tramal hyphae subparallel, subhymenial hyphae short-celled, 1.9–3.9 μm in diam. (n=30/3). Large rhomboid or stellate crystals rarely present in trama and subiculum, 10–19 μm in diam. Cystidia of three types: a) large, thin- or fairly thick-walled (wall up to 2.8 μm thick) cystidia of subicular, tramal or subhymenial origin, cylindrical, spathuliform, almost capitate or with one intercalary inflation at the upper part, (64.0–)71.0–188.9(–220.0)×(5.0–)5.7–9.4(–11.9) μm (n=30/3), often apically encrusted by large rhomboid crystals, b) astrocystidia of subhymenial origin, bearing a stellate crystalline cap 15–17×4.5–4.8 μm, sometimes rare, c) cystidia of subhymenial origin, thin-walled, varying from fusoid to cylindrical or submoniliform, rarely forked, 40.0–84.0(–92.0)×5.0–9.0(–11.4) μm (n=30/3). Basidia suburniform, 4-spored, 14.7–22.8(–24.0)×3.4–4.9 μm (n=30/3), thin-walled. Basidiospores clearly thick-walled, ellipsoid to broadly ellipsoid, usually with an oil-drop, (4.8–)5.1–6.0×3.8–4.6 μm (n=92/3), L=5.48, W=4.21, Q=1.30, cyanophilous.

Figure 12. 

Xylodon ussuriensis (holotype): a section through an aculeus b basidia, basidioles and hymenial cystidia c thick- and thin-wall tramal cystidia d thick- and thin-wall subhymenial cystidia e astrocystidia f basidiospores h short-celled hyphae from aculei.

Distribution and ecology

East Asia (Russian Far East – Primorie), on decayed angiosperm wood; seemingly not rare in secondary oak-dominated forest.

Remarks

The distinctly thick-walled tubular cystidia of X. ussuriensis make it different from other Lagarobasidium-like species treated here. Subhymenial astrocystidia found in X. ussuriensis are also present in some specimens of X. detriticus although they are apparently rare in the latter species.

Discussion

Our study confirms the results from Larsson et al. (2006) and Larsson (2007) that Peniophora detritica clusters with Xylodon quercinus, the type species of Xylodon. Here we also show that Peniophora pruinosa, the type of Lagarobasidium, belongs in Xylodon and is a sister species to X. detriticus. This contradicts the results published by Dueñas et al. (2009) who came to the conclusion that Lagarobasidium was a genus separate from Hyphodontia sensu lato. As support for that result, they published ITS sequences of L. detriticum and the new species L. calongei (GenBank FM876211 and FM876212, respectively). However, at least the sequence of L. detriticum (FM876211) seems to be based on a misidentification or contamination during the laboratory process. This sequence is 100% identical to several sequences of Hyphoderma roseocremeum, a species belonging in Polyporales (e.g. UNITE database UDB031922).

Blasting FM876212 against public sequence databases does not return any reliable results, which, if the sequence is correct, suggests that the species does not belong in Xylodon. Remaining species referred to Lagarobasidium and not already discussed include L. cymosum (D.P. Rogers & H.S. Jacks.) Jülich and L. subdetriticum (S.S. Rattan) J. Kaur & Dhingra. The former has been placed in Hypochnicium because of the thick-walled basidiospores but numerous subulate cystidia makes it a deviating element in that genus. Only access to sequence information can disclose its relationships. Lagarobasidium subdetriticum was originally described in Hyphodontia and should be retained in that genus also when the genus is taken in a restricted sense (Hjortstam and Ryvarden 2009).

For the phylogenetic analyses of Hyphodontia sensu lato, only nuclear ribosomal genes have so far been applied. All published results confirm that Hyphodontia sensu lato is polyphyletic and that most species can be referred to one of three clusters, viz Hyphodontia sensu stricto, the Kneiffiella cluster and the Xylodon cluster (including Lyomyces). Within these clusters the relationships are not well resolved when the ribosomal genes are the sole source for genetic information. On such detailed level, analyses become highly sensitive to sampling and outgroup choice. It is clear that both a wider sampling and more markers must be included in analyses in order to establish a stable genus level classification for all species that have been referred to Hyphodontia in a wide sense.

Acknowledgements

Curators of herbaria S, GB, BPI, TAAM and BAFC sent us types and other herbarium specimens used in the present study. The first author is grateful to the Kedrovaya Pad Nature Reserve staff, in particular, to Gleb Sedash and Dina Matyukhina. We also thank Eugeny Antonov and Fedor Bortnicov (Moscow) for their assistance during fieldwork and providing valuable fungal collections.

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