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Four new East Asian species of Aleurodiscus with echinulate basidiospores
expand article infoSheng-Hua Wu, Chia-Ling Wei, Yu-Ting Lin, Chiung-Chih Chang, Shuang-Hui He§
‡ National Museum of Natural Science, Taichung, Taiwan
§ Beijing Forestry University, Beijing, China
Open Access

Abstract

Four new species of Aleurodiscus sensu lato with echinulate basidiospores are described from East Asia: A. alpinus, A. pinicola, A. senticosus, and A. sichuanensis. Aleurodiscus alpinus is from northwest Yunnan of China where it occurs on Rhododendron in montane habitats. Aleurodiscus pinicola occurs on Pinus in montane settings in Taiwan and northwest Yunnan. Aleurodiscus senticosus is from subtropical Taiwan, where it occurs on angiosperms. Aleurodiscus sichuanensis is reported from southwest China on angiosperms in montane environments. Phylogenetic relationships of these four new species were inferred from analyses of a combined dataset consisting of three genetic markers, viz. 28S, nuc rDNA ITS1-5.8S-ITS2 (ITS), and a portion of the translation elongation factor 1-alpha gene, TEF1.

Keywords

China, corticioid fungi, Taiwan, taxonomy, wood-decaying fungi

Introduction

The genus Aleurodiscus Rabenh. ex J. Schröt. belongs to the Stereaceae Pilát of the Russulales Kreisel ex P.M. Kirk, P.F. Cannon & J.C. David. However, whether to keep Aleurodiscus in a broad or a narrow sense has long been a puzzling issue in the taxonomy of Basidiomycota (Boidin et al 1985; Núñez and Ryvarden 1997; Wu et al. 2001; Larsson and Larsson 2003; Miller et al. 2006; Larsson 2007; Wu et al. 2010), because diagnostic characters are highly variable among species. Aleurodiscus s.l. is characterized by cupulate, effused or effused-reflexed basidiocarps, a monomitic or dimitic hyphal system with simple-septate or clamped generative hyphae, smooth or ornamented amyloid basidiospores, and sterile organs such as acanthophyses, gloeocystidia, hyphidia, and dendrohyphidia (Núñez and Ryvarden 1997). The characteristics used for separating segregate genera within Aleurodiscus s.l. (Acanthobasidium Oberw., Acanthofungus Sheng H. Wu et al, Acanthophysellum Parmasto, Aleurobotrys Boidin, Aleurodiscus s.s., Aleurocystidiellum P.A. Lemke, Gloeosoma Bres., and Neoaleurodiscus Sheng H. Wu) as well as Stereum Hill ex Pers. and Xylobolus P. Karst. were provided by Wu et al. (2001, table 1) and Wu et al. (2010, table 1). Currently, 169 names are recorded under Aleurodiscus, of which about 85 taxa are generally accepted worldwide (http://www.indexfungorum.org/). Since the year 2000, new species of Aleurodiscus s.l. have been proposed by Simpson and Grgurinovic (2003), Hjortstam et al. (2009), Ryvarden et al. (2012), Gorjón et al. (2013), Maninder et al. (2014), Dai and He (2016), Dai et al. (2017a, b), Ghobad-Nejhad and Langer (2018), and Tian et al. (2018). Since the phylogenetic relationships of the taxa in Aleurodiscus s.l., as well as in the Stereaceae at large, are not resolved, we adopt a broad and inclusive generic concept of Aleurodiscus for the new taxa presented in this study.

During a two-decade long, ongoing survey of corticioid fungi from mainland China and Taiwan, we have found four new species of Aleurodiscus with echinulate basidiospores based on morphological characters. In addition, phylogenetic analyses of a nuclear rDNA 28S D1–D2 domains (28S) dataset and analyses of a second dataset consisting of three genetic markers – nuc rDNA 28S D1–D2 domains (28S), nuc rDNA ITS1-5.8S-ITS2 (ITS), and translation elongation factor 1-alpha (TEF1) – are performed to complement our morphological observations and place the newly described species in a molecular phylogenetic framework.

Materials and methods

Morphological and cultural studies

Macroscopic and microscopic studies were based on dried specimens. Color names from Rayner (1970) are capitalized. Thin free-hand sections of basidiocarps were prepared for microscopic study. For observations and measurements of microscopic characters, sections were mounted in 5% KOH to ensure rehydration. A blue-black color change with Melzer’s reagent (IKI) indicates an amyloid reaction. Cotton blue (CB) was used as mounting medium to determine cyanophily. Sulphoaldehyde (SA) was used to detect a sulphuric reaction of gloeocystidia; a bluish black color change with SA indicates a positive reaction. The following abbreviations are used for basidiospore measurements: L = mean spore length with standard deviation, W = mean spore width with standard deviation, Q = variation in L/W ratio, and n = number of spores measured from each specimen. Apiculi and ornamentation were excluded in spore measurements. Living mycelia were isolated from the woody substratum beneath the basidiocarps, and were cultured on 1.5% malt extract agar (MEA). Fungal specimens and living cultures used in this study are deposited in the herbaria of the National Museum of Natural Science of ROC (TNM; Taichung City, Taiwan) and Beijing Forestry University (BJFC; Beijing, China).

DNA extraction, polymerase chain reaction (PCR), and sequencing

Dried specimens or the mycelial colonies cultured on MEA were used for DNA extraction, carried out with a Plant Genomic DNA Extraction Miniprep System (Viogene-Biotek Corp., New Taipei City, Taiwan). Liquid N and Tissue Lyser II (Qiagen, Hilden, Germany) were used to disrupt and homogenize the fungal tissues before DNA extraction process. The primer pairs ITS1/ITS4 or ITS1F/LR22 were used for the ITS region (White et al. 1990, Gardes and Bruns 1993), and LR0R/LR3 and LR0R/LR5 were used for the 28S region (Vilgalys and Hester 1990). Efdf/1953R and 983F/2218R were used to amplify a portion of the TEF1 gene (Rehner & Buckley 2005; Matheny et al. 2007). PCR products were purified and directly sequenced by MB Mission Biotech Company (Taipei City, Taiwan). We examined the technical quality of the newly obtained sequences by comparison to entries in GenBank. Sequences were assembled using BioEdit v7.2.5 (Hall 1999). Newly obtained sequences (Supplementary Table 1) were submitted to either GenBank through the National Center for Biotechnology Information (NCBI) or DNA Data Bank of Japan (DDBJ) (Mashima et al. 2016, Benson et al. 2018).

Alignment and phylogenetic analyses

The newly generated sequences were added to the DNA sequence dataset employed by Dai and He (2016), so far the most inclusive alignments for analyzing Aleurodiscus s.l. based on three genetic markers. To achieve a comprehensive analysis, we also added some related taxa of the genera Boidinia Stalpers & Hjortstam, Conferticium Hallenb., Gloeocystidiellum Donk and Megalocystidium Jülich to the ingroup. We tried to include the type species of the genera as far as possible (Table 1). The phylogenetic tree of the 28S+ITS+ TEF1 dataset was inferred through Maximum likelihood (ML) and Bayesian inference (BI) methods using RAxML v. 8.2.4 (Stamatakis 2014) and MrBayes v. 3.2.6 (Ronquist et al. 2012), respectively (Ronquist et al. 2012, Stamatakis 2014). The alignments were inferred in MAFFT v. 7 using the FFT-N-i strategy for 28S and TEF1, and Q-INS-i strategy for ITS. For the BI analysis, the best-fit model for each alignment partition was estimated by jModelTest 2 (Darriba et al. 2012) using the Akaike information criterion (AIC). For ML bootstrapping, the extended majority-rule consensus tree criterion was specified under a GTRGAMMA model with 1000 replicates. In the BI analysis, four MCMC chains were run simultaneously from a random starting tree for ten million generations. Trees were sampled every 1000 generations resulting in 10000 trees in the posterior distribution; the first 25% trees were discarded as the burn-in. Posterior probabilities (PP) were calculated based on the post-burn-in trees. ML bootstrap values (BS) and BI posterior probability (PP) values ≥ 50% and ≥ 0.7 are indicated at the nodes of the ML tree. The final sequence alignments and the phylogenetic trees are available at TreeBASE (S23581; www.treebase.org).

List of species, specimens and sequences used in this study. Sequences generated in this study are shown in boldface.

Fungal species Specimen or strain no. DDBJ/GenBank/EMBL accession no.
ITS 28S TEF1
Acanthobasidium bambusicola He2357 KU559343 KU574833
Acanthofungus rimosus# Wu9601-1 MF043521 AY039333
Acanthophysellum cerussatum He20120920-3 KU559339 KU574830 KU992716
Aleurobotrys botryosus# He2712 KX306877 KY450788
Aleurocystidiellum disciforme He3159 KU559340 KU574831 KU992721
Aleurocystidiellum subcruentatum# He2886 KU559341 KU574847 KU992720
Aleurodiscus alpinus Wu1407-59 MF043522 MF043527
Aleurodiscus alpinus Wu1407-55* MF043526 LC269190
Aleurodiscus alpinus Wu1407-61 MF043523 MF043528
Aleurodiscus amorphus# Ghobad-Nejhad-2464 KU559342 KU574832 KU992717
Aleurodiscus amorphus# KHL4240 AF506397 AF506397
Aleurodiscus bambusinus He 4261 KY706207 KY706219 LC430911
Aleurodiscus canadensis Wu 1207-90 KY706203 KY706225
Aleurodiscus dextrinoideocerussatus EL25-97 AF506401 AF506401
Aleurodiscus dextrinoideophyses He 4105 MH109050 KY450784
Aleurodiscus effusus He2261 KU559344 KU574834 KU992719
Aleurodiscus gigasporus Wu 0108-15 KY706205 KY706213
Aleurodiscus grantii HHB-14417 KU559363 KU574821 KU992708
Aleurodiscus grantii HHB-14418 KU559364 KU574822
Aleurodiscus isabellinus He 5283 MH109052 MH109046 LC430912
Aleurodiscus mesaverdense FP-120155 KU559359 KU574817
Aleurodiscus mirabilis Dai13281 KU559350 KU574839 KU992711
Aleurodiscus oakesii He2243 KU559352 KU574840
Aleurodiscus oakesii HHB11890-A-sp KU559365 KU574823
Aleurodiscus pinicola Wu1106-16 MF043524 MF043529
Aleurodiscus pinicola Wu1308-54* MF043525 MF043530 LC269191
Aleurodiscus senticosus Wu1209-7* MH596849 MF043531 LC271169
Aleurodiscus senticosus Wu1209-9 MH596850 MF043533 LC269192
Aleurodiscus senticosus Wu9610-1 MH596851 MF043532 LC269193
Aleurodiscus sichuanensis Wu0010-18* MH596852 MF043534 LC269194
Aleurodiscus sichuanensis He 4935 LC430904 LC430907
Aleurodiscus subroseus He 4807 MH109054 MH109048
Aleurodiscus subroseus He 4895 LC430903 LC430910 LC430913
Aleurodiscus tenuissimus He3575 KX306880 KX842529
Aleurodiscus thailandicus He 4099 KY450781 KY450782
Aleurodiscus tropicus He3830 KX553875 KX578720 LC269195
Aleurodiscus verrucosporus He 4491 KY450786 KY450790
Aleurodiscus wakefieldiae He2580 KU559353 KU574841 KU992710
Boidinia macrospora Wu9202-21 AF506377 AF506377
Conferticium heimii CBS321.66 AF506381 AF506381
Conferticium ravum NH13291 AF506382 AF506382
Gloeocystidiellum aspellum LIN625 AF506432 AF506432
Gloeocystidiellum porosum # Wu 1608-176 LC430905 LC430908
Gloeocystidiopsis cryptacanthus KHL10334 AF506442 AF506442
Gloeocystidiopsis flammea# CBS324.66 AF506437 AF506437
Heterobasidion parviporum 91605 KJ651503 KJ651561 KU985089
Megalocystidium chelidonium LodgeSJ110.1 AF506441 AF506441
Megalocystidium leucoxanthum# HK9808 AF506420 AF506420
Megalocystidium wakullum Oslo-930107 AF506443 AF506443
Neoaleurodiscus fujii# He2921 KU559357 KU574845 KU992709
Stereum complicatum He2234 KU559368 KU574828 KU992706
Stereum hirsutum# Wu 1109-127 LC430906 LC430909
Stereum ostrea SHe2067 KU559366 KU574826 KU992703
Stereum sanguinolentum He2111 KU559367 KU574827 KU992705
Xylobolus frustulatus He2231 KU881905 KU574825 KU992704

Phylogeny results

The three-marker dataset was composed of 55 taxa and 2502 sites including gaps (of which 29% were parsimony-informative): 953 characters for 28S, 949 characters for ITS and 600 characters for TEF1. Missing sequences were treated as missing data (Table 1). After the ML search, 1000 rapid bootstrap inferences were executed. For the BI analysis, the GTR+I+G model was chosen as the best model for the 28S and TEF1 alignments, and GTR+G was chosen for the ITS alignment. After 2.79 million generations, average standard deviation of split frequencies fell to 0.0099. Only the ML tree is shown given that the ML and BI analyses yielded similar topologies. The ML tree of the combined 28S, ITS and TEF1 dataset (Fig. 1) showed that strains of Aleurodiscus alpinus, A. pinicola, A. sichuanensis, and A. senticosus formed separate clades in distinct lineages with high statistical support (BS = 96–100%, PP = 1). The strain of A. sichuanensis was sister to A. alpinus with significant support, BS: 90% and PP: 1.

Figure 1. 

ML tree of Aleurodiscus and related genera of Stereaceae inferred from the 28S-ITS-TEF1 markers. ML bootstrap values ≥ 50% and PP ≥ 0.7 from the Bayesian analysis are indicated at internodes. The presented new species are shown in boldface type.

Taxonomy

Aleurodiscus alpinus Sheng H. Wu, sp. nov.

MycoBank No: 823178
Figs 2A, 3

Typification

CHINA. YUNNAN PROVINCE: Shangrila County, Pudacuo National Park, Bita Lake, 27°43'N, 99°58'E, 3640 m, on branch of Rhododendron sp., 10 Jul 2014, S.H. Wu, Wu 1407-55 (holotype TNM F27976). GenBank 28S = MF043526, TEF1 = LC269190.

Etymology

alpinus (L.), referring to the occurrence at high elevations.

Diagnosis

Resembles Aleurodiscus cupulatus Núñez & Ryvarden in having discoid basidiomes, clamped hyphae, similar gloeocystidia, absence of acanthophyses, branched or unbranched hyphidia, and echinulate basidiospores. Aleurodiscus cupulatus features much wider basidiospores than A. alpinus. It differs from its closest phylogenetic relative, A. sichuanensis, by having clamped hyphae, but lacks acanthophyses.

Description

Basidiomes cupuloid or discoid, solitary, occasionally fused, adnate, 350–750 μm thick in section. Hymenial surface Buff, Pale Luteous or Luteous, subceraceous, covered with crystal masses, not cracked; margin concolorous or paler, incurved, filamentous.

Hyphal system monomitic; hyphae nodose-septate. Pileus hyphae subcolorless to brownish, straight, thick-walled, walls usually thinner towards apices, usually with excreted material near apices. Subiculum uniform, with dense to compact texture, 150–500 μm thick; hyphae near substrate more or less vertical, moderately ramified, colorless, 3.5–8 μm diam, with 0.7–1.5 μm thick walls, occasionally guttulate; hyphae near hymenial layer more or less vertical, moderately ramified, colorless, fairly straight, 2.5–5 μm diam, thin- or slightly thick-walled, anastomoses occasional. Hymenial layer thickening, subhymenium differentiated from subiculum, 200–250 μm thick, with dense texture; hyphae fairly vertical, colorless, guttulate, 2–4 μm diam, thin-walled. Crystals sparsely scattered throughout section. Gloeocystidia numerous, immersed or slightly projecting, tubular, sometimes with adventitious septa near basal parts, colorless, (50–)70–200 × 4.5–12.5 μm, thin-walled, guttulate, SA+. Hyphidia numerous, sometimes branched, 40–130 × 2–6.5 μm. Basidia narrowly clavate, occasionally with one or two small protuberances, 85–165 × 16–20 μm, slightly thick-walled (ca. 0.5 μm thick), 4-sterigmate. Basidiospores ellipsoid to narrowly ellipsoid, adaxially concave, finely aculeate, thin-walled, homogenous or guttulate, amyloid, CB–, mostly 22–26 × 11–14 μm. (22–)22.2–26(–27.8) × (11–)11.8–13.5(–14.8) μm, L = 24.2±1.7 μm, W = 12.6±2.2 μm, Q = 1.95 (n = 30) (holotype, Wu 1407-55); (22–)23–24.5(–26) × (10.2–)10.8–13(–14) μm, L = 23.8±1.0 μm, W = 11.8±1.0 μm, Q = 2.02 (n = 30) (Wu 1407-59).

Figure 2. 

Basidiocarps A Aleurodiscus alpinus (holotype, Wu 1407-55) B A. pinicola (holotype, Wu 1308-54) C A. senticosus (holotype, Wu 1308-54) D A. sichuanensis (holotype, Wu 0010-18).

Ecology and distribution

On dead branches of Rhododendron and other angiosperms at very high elevations, China, Jul.

Additional specimens examined

CHINA. YUNNAN PROVINCE: Shangrila County, Pudacuo National Park, Bita Lake, 27°43'N, 99°58'E, 3640 m, on branch of Rhododendron sp., 10 Jul 2014, S.H. Wu, Wu 1407-59 (TNM F27979), Wu 1407-61 (TNM F27981); Pudacuo National Park, 3600 m, on dead branch of Rhododendron sp., 28 Jul 2017, S.H. He, He 4924 (BJFC), He 4942 (BJFC); Jianchuan County, Laochunshan, 26°38'N, 99°47'E, 3400 m, on angiosperm branch, 26 Jul 2001, S.H. Wu & S.Z. Chen, Wu 0107-22 (TNM F13507), Wu 0107-25 (TNM F13510).

Figure 3. 

Microscopic structures of Aleurodiscus alpinus (holotype, Wu 1407-55) A profile of basidiocarp section B subhymenial and hymenial section C basidiospores (far right: in IKI) D subicular hyphae near substrate E pileus hyphae F subhymenial hyphae G hyphidia H branched hyphidia I gloeocystidia J basidia. Bars: 300 μm (A); 10 μm (B–J).

Aleurodiscus pinicola Sheng H. Wu, sp. nov.

MycoBank No: 823179
Figs 2B, 4

Typification

CHINA. YUNNAN PROVINCE: Lichiang, High Mountain Workstation of Kunning Botanical Garden, 27°00'N, 100°11'E, 3250 m, on branch of Pinus densata, 30 Aug 2013, S.H. Wu, Wu 1308-54 (holotype TNM F27182). GenBank: ITS = MF043525, 28S = MF043530, TEF1 = LC269191.

Etymology

pinicola (L.), dwelling on Pinus, in reference to the substrate.

Diagnosis

Aleurodiscus pinicola and Acanthobasidium penicillatus Burt share the features of moniliform gloeocystidia, acanthophyses with apical spines, dendrohyphidia, basidia with lateral protuberances, and aculeate basidiospores; the latter, however, has clamped hyphae and narrower basidiospores 18–27 × 12–14 (–17) μm. Aleurodiscus pinicola also resembles A. oakesii (Berk. & M.A. Curtis) Pat., however, the latter occurs on deciduous trees and has smaller basidiospores (15–20 × 13–17 μm).

Basidiomes discoid, each one up to 3.5 × 3 mm, adnate, membranaceous-subceraceous, 180–400 μm thick in section. Hymenial surface Buff or Pale Luteous, smooth, occasionally cracked; margin whitish, incurved, filamentous.

Hyphal system monomitic; most hyphae simple-septate, a few hyphal septa in junction of hymenium and subiculum with clamp connections. Subiculum uniform, with fairly dense dense texture, 60–160 μm thick; hyphae more or less vertical at resupinate parts, ± horizontal at marginal curved parts, moderately ramified, more or less interwoven, colorless, 2.5–6 μm diam, slightly thick-walled or containing thick walls up to 2 μm thick, sometimes with small oily drops, anastomoses occasional, some basal hyphae brownish yellow, with thicker walls than those elsewhere. Hymenial layer thickening, subhymenium more or less differentiated from subiculum, with dense texture, 100–270 μm thick; hyphae more or less vertical, colorless, sometimes with a short branch, usually containing minute oily drops, 2.5–5.5 μm diam, thin-walled. Crystal masses scattered throughout hymenial layer. Gloeocystidia numerous, mostly immersed or slightly projecting, cylindrical, usually strongly moniliform toward apices, usually forked, with numerous minute oily drops, colorless, 65–200 × 8.2–15.5 μm, thin- to slightly thick-walled, SA–. Acanthophyses numerous, clavate to broadly clavate, fusiform, stalked, colorless, apical parts with numerous protuberances, 50–100 × 5–30 μm, up to 1.2 μm thick walls, aculei 1–7 × 1–2 μm. Dendrohyphidia numerous, 37–90 × 3–4.8 μm. Hyphidia numerous, 35–80 × 2.4–4.2 μm. Basidia clavate, middle parts usually with several protuberances, 65–130 × 20–32 μm, up to 1.2 μm thick walls, 4-sterigmate. Basidiospores broadly ellipsoid to subglobose, adaxially flattened, aculeate, thin- to thick-walled, up to 3 μm thick walls, with a distinct apiculus, homogenous or with several oil-drops, amyloid, CB–, mostly 22.5–27.5 × 19–24 μm. (22.5–)23.5–27.2(–29) × (18.2–)19.2–22.8(–24) μm, L = 25.4±1.3 μm, W = 20.7±1.6 μm, Q = 1.23 (n = 30) (holotype, Wu 1308-54); (22.2–)23–26.5(–28) × (18.2–)20–22.5(–25.5) μm, L = 24.8±1.3 μm, W = 21.2±1.5 μm, Q = 1.17 (n = 30) (Wu 1106-14).

Figure 4. 

Microscopic structures of Aleurodiscus pinicola (holotype, Wu 1308-54) A profile of basidiocarp section B subicular hyphae of basidiocarp section C subhymenial and hymenial section D generative hyphae E hyphidia F dendrohyphidia G acanthophyses H gloeocystidia I basidia J basidiospores (left: in IKI, right: in KOH). Scale bars: 200 μm (A); 10 μm (B–J).

Ecology and distribution

On Pinus branches at high elevations, China and Taiwan, Jun to Aug.

Additional specimens examined

TAIWAN. Taichung, Siaosyueshan, Tienchih, 24°17'N, 121°01'E, 2580 m, on branch of Pinus armandii, 8 Jun 2011, S.H. Wu, Wu 1106-14 (TNM F25532); ibid. Wu 1106-16 (TNM F25534).

Aleurodiscus senticosus Sheng H. Wu, sp. nov.

MycoBank No: 823180
Figs 2C, 5

Typification

TAIWAN. New Taipei City, Wulai, 24°51'N, 121°33'E, 448 m, on branch of angiosperm, 10 Sep 2012, S.H. Wu, Wu 1209-7 (holotype TNM F26702). GenBank: ITS = MH596849, 28S = MF043531, TEF1 = LC271169.

Etymology

senticosus (L.) = full of thorns, referring to the surface of basidia and cystidia.

Diagnosis

Macroscopically featured in having a more or less cracked hymenophore, resulting from the fusion of numerous basidiome patches. Microscopically its basidia are diagnostic in having large lateral echinulate bladder-like swollen structure. Morphologically it resembles Xylobolus spp., although the latter cause a white-pocket rot in wood and have smooth basidiospores.

Description

Basidiomes resupinate, beginning as small orbicular patches, gradually extending and fusing together then becoming effused, adnate, membranaceous, 250–600 μm thick in section. Hymenial surface Buff or Light Buff, slightly tuberculate, with a more or less cracked hymenophore; margin paler, usually determinate, occasionally thinning and byssoid.

Hyphal system monomitic; hyphae simple-septate, colorless. Subiculum with dense texture, 200–350 μm thick; hyphae next to substrate more or less horizontal, slightly interwoven, colorless, moderately ramified, at the junction of basidiocarp patches more or less vertical, 2–4(–5) μm diam, walls up to 1.5 μm thick. Hymenial layer thickening, with dense texture, 150–250 μm thick, not clearly differentiated from the subiculum; hyphae mainly vertical, colorless, 2–4 μm diam, thin- to slightly thick-walled. Gloeocystidia numerous, immersed or slightly projecting, cylindrical or tubular, with stalked bases, apically sometimes forked, sometimes with one or more constrictions near apices or slightly moniliform, colorless, 45–135 × 5–12 μm, with walls up to 1.5 μm thick, SA–. Acanthophyses numerous, subclavate or clavate, basal parts thin-walled, thick-walled toward apices, colorless, median to apical parts echinulate, 25–65 × 4–13 μm (spines excluded). Hyphidia numerous, 35–65 × 2–4 μm. Basidia clavate, 60–82 × 10–15 μm, with walls up to 2 μm thick, 4-sterigmate, usually with large lateral echinulate bladder-like swollen structure. Basidiospores broadly ellipsoid to subglobose, adaxially flattened, aculeate, with 1–3 μm thick walls, homogeneous or sometimes with several oily drops, amyloid, CB–, mostly 13.5–16.5 × 11–13 μm. (13–)13.5–15.8(–17) × (10–)11.2–12.5(–13) μm, L = 14.8±1.00 μm, W = 11.8±0.6 μm, Q = 1.25 (n = 30) (holotype, Wu 1209-7); (13–)14–16(–17.2) × (10–)11.2–13(–15) μm, L = 15.1±1.0 μm, W = 11.9±1.0 μm, Q = 1.26 (n = 30) (GC 1604-46).

Figure 5. 

Microscopic structures of Aleurodiscus senticosus (holotype, Wu 1209-7) A profile of basidiocarp section B basal of basidiocarp section C section of hymenium D subicular hyphae E gloeocystidia F acanthophyses G basidiospores (left: in KOH, right: in IKI) H hyphidia I basidia. Scale bars: 200 μm (A); 10 μm (B–I).

Ecology and distribution

On angiosperm branches, Taiwan, Apr to Sep.

Additional specimens examined

Taiwan, New Taipei City, Wulai, 24°51'N, 121°33'E, 448 m, on angiosperm branch, 10 Sep 2012, S.H. Wu, Wu 1209-9 (TNM F26704); Nantou, Lienhuachih. 23°56'N, 120°53'E, 700 m, on angiosperm branch, 08 Oct 1996, S.H. Wu, Wu 9610-1 (TNM F5344); on angiosperm branch, 09 Apr 2016, G.C. Chen, GC 1604-46 (TNM F30771).

Aleurodiscus sichuanensis Sheng H. Wu, sp. nov.

MycoBank No: 823181
Figs 2D, 6

Typification

CHINA. SICHUAN PROVINCE: Wolungshan, Tengsheng, 2700 m, under bark of angiosperm, 11 Oct 2000, S.H. Wu & S.C. Wu, Wu 0010-18 (holotype TNM F12097). GenBank: ITS = MH596852, 28S = MF043534, TEF1 = LC269194.

Etymology

sichuanensis (L.), referring to Sichuan Province, the type locality.

Diagnosis

Aleurodiscus sichuanensis resembles A. oakesii in having acanthophyses, simple-septate generative hyphae, and gloeocystidia occasionally with protuberances. However, clamped hyphae are rarely present in A. oakesii. Protuberances of acanthophyses of A. oakesii are antler-like, while aculei of acanthophyses in A. sichuanensis are fairly small. Basidiospores of A. sichuanensis are D-shaped or broadly ellipsoid, while those of A. oakesii are ovoid-ellipsoid and slightly smaller (18–27 ×12–14(–17) μm). Aleurodiscus sichuanensis, however, is most closely related to A. alpinus and differs from it by having acanthophyses and simple-septate hyphae.

Basidiomes resupinate, effused, adnate, membranaceous-subceraceous, 150–350 μm thick in section. Hymenial surface smooth, Buff or Buff Yellow, occasionally cracked; margin concolorous, determinate.

Hyphal system monomitic; hyphae simple-septate. Subiculum uniform, with dense texture, thin or up to 150 μm thick; hyphae interwoven, colorless, richly ramified, tortuous, usually full of small oily drops, 2.5–5.5 μm diam, thin-walled. Hymenial layer with dense texture, 100–200 μm thick; hyphae vertical, colorless, ± straight, 2.5–4.5 μm diam, thin-walled. Crystal masses scattered in subiculum, yellowish. Gloeocystidia numerous, immersed or projecting, yellowish or pale brownish yellow, cylindrical, narrowly clavate or tubular, with oily contents or homogeneous, SA+, basal or median portion occasionally with small aculei, 70–135 × 7–14 μm, with 0.5–1 μm thick walls. Acanthophyses numerous, irregularly cylindrical or narrowly clavate, sometimes subfusiform, colorless, apical parts with numerous aculei, 30–70 × 3–8(–12) μm (aculei excluded), thin-walled. Hyphidia numerous, occasionally branched, 35–85 × 2.5–4.5 μm. Basidia clavate, 4-sterigmate, 100–130 × 20–25 μm, with 0.8–1.2 μm thick walls. Basidiospores D-shaped or broadly ellipsoid, adaxially flattened, finely aculeate, thin-walled or 1–2 μm thick, sometimes with oily contents, amyloid, CB–, mostly 25.5–28.5 × 15–18 μm. (25–)26–28.2(–29) × (14.5–)15.2–17(–19) μm, L = 27.1±1.0 μm, W = 15.9±1.1 μm, Q = 1.71 (n = 30) (holotype, Wu 0010-18).

Figure 6. 

Microscopic structures of Aleurodiscus sichuanensis (holotype, Wu 0010-18) A basidiocarp section B subicular hyphae C hyphidia D acanthophyses E basidiospores (upper: in IKI, lower: in KOH) F basidia G gloeocysitidia. Scale bars: 10 μm.

Ecology and distribution

On dead branches of Quercus and other angiosperms at high elevations, China, Jul to Oct.

Additional specimens examined

CHINA. SICHUAN PROVINCE: Wolungshan, Tengsheng, 2700 m, on angiosperm branch, 11 Oct 2000, S.H. Wu & S.C. Wu, Wu 0010-42 (TNM F12118). YUNNAN PROVINCE: Shangrila County, Pudacuo National Park, 3600 m, on dead branch of Quercus apuifolloides, 28 Jul 2017, S.H. He, He 4923, He 4926, He 4930, He 4935 (BJFC).

Discussion

A number of phylogenetic studies of Aleurodiscus s.l. have been conducted in the past twenty years (Wu et al. 2001; Larsson and Larsson 2003; Miller et al. 2006; Larsson 2007; Dai and He 2016; Dai et al. 2017). Miller et al. (2006) and Larsson (2007) tried to establish a family level classification for Aleurodiscus s.l., as well as related taxa of the Russulales. However, a fully resolved and robust phylogeny of Aleurodiscus s.l. and related taxa was not achievable with ribosomal genes alone. Dai and He (2016) and our study have addressed this by including TEF1 for phylogenetic analyses. From our phylogenetic analyses of three DNA genetic markers (Fig. 1) we can conclude the following about evolutionary relationships in the Stereaceae: (i) Aleurodiscus s.l. is highly polyphyletic; (ii) Acanthophysellum is polyphyletic; (iii) Gloeocystidiellum is polyphyletic; (iv) Megalocystidium is polyphyletic; and (v) Conferticium is paraphyletic.

Aleurodiscus alpinus is reminiscent of Aleurodiscus s.s. (A. amorphus (Pers.) J. Schröt. and A. grantii Lloyd) due to the discoid basidiocarp and echinulate basidiospores, as well as the absence of acanthophyses. However, the gloeocystidia of Aleurodiscus s.s. are paraphysis-like, narrow and moniliform, while those of A. alpinus are much wider and not moniliform. In addition, A. alpinus has unbranched or branched hyphidia, which are lacking in Aleurodiscus s.s. Aleurodiscus alpinus formed a clade with A. sichuanensis (Fig. 1), however, the latter has simple-septate hyphae and acanthophyses. Aleurodiscus alpinus and A. cupulatus share most morphological features, except the latter has much wider basidiospores. Aleurodiscus alpinus grows on Rhododendron sp. in Yunnan of China, while A. cupulatus occurs on Pseudotsuga menziesii in Idaho of USA. No DNA sequence of the latter has been obtained to examine their relationship.

Aleurodiscus pinicola presents protuberances in the basidia and this is reminiscent of Acanthobasidium. However, this feature is not limited to Acanthobasidium spp. For example, basidia of Aleurodiscus mirabilis (Berk. & M.A. Curtis) Höhn. and A. wakefieldiae Boidin & Beller occasionally possess protuberances, but they and A. pinicola do not belong to Acanthobasidium (Fig. 1).

Aleurodiscus senticosus is macroscopically distinct in having more or less cracked hymenophore from the fusion of smaller basidiocarp patches; microscopically, its basidia bear a large, spiny, bladder-like structure that is unique among Aleurodiscus s.l. The present phylogenetic analyses (Fig. 1) indicated that A. senticosus formed a clade with Xylobolus and Acanthofungus, but without strong support. However, these two genera differ from A. senticosus by causing a white-pocket rot in wood and by bearing smooth basidiospores.

Aleurodiscus sichuanensis cannot be accommodated in any segregate genus of Aleurodiscus s.l., according to the combined features of effused basidiocarp, simple-septate hyphae, acanthophyses, gloeocystidia with aculei, and echinulate basidiospores.

In conclusion, the status of each segregate genus of Aleurodiscus s.l. should be further examined by multi-gene analysis of more species to evaluate which ones can be recognized and which cannot. Although the four new species we introduce cannot be accommodated in any segregate genus of Aleurodiscus s.l. according to the present combined morphological and phylogenetic studies, they are still placed under the broad sense of Aleurodiscus at the present time.

Acknowledgments

This study was financed by Ministry of Science and Technology of R.O.C. (Grant no 104-2621-B-178-001-MY3). The authors are grateful to Ms. Siou-Zhen Chen (TNM) for contributing the photos of the basidiocarps, and managing studied specimens.

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