Sixteen studied specimens were sampled in northwestern and southwestern China, Vietnam, and Australia from May to November 2017–2020. These specimens were dried using a portable drying instrument at 35°C on the day of sampling and are preserved at the Fungarium, Institute of Microbiology, Chinese Academy of Sciences (HMAS), Beijing, China and the National Herbarium of Victoria (MEL), Melbourne, Australia. Macromorphological characters of basidiomes were examined with the aid of a Leica M125 stereomicroscope (Wetzlar, Germany) at magnifications up to 100 × . Color terms follow Petersen (1996). Microscopic examination was carried out with an Olympus BX43 light microscope (Tokyo, Japan) at magnifications up to 1,000 × following a study by Liu et al. (2021). All the measurements were taken from the sections mounted in cotton blue. The following abbreviations are used: L = mean basidiospore length (arithmetic average of all the basidiospores), W = mean basidiospore width (arithmetic average of all the basidiospores), Q = variation in the L/W ratios between the specimens studied, and n = number of basidiospores measured from a given number of specimens.

The cetyltrimethylammonium bromide (CTAB) plant genome rapid extraction kit (Beijing Demeter Biotech Co., Ltd., Beijing, China) was employed for DNA extraction from dried specimens. The internal transcribed spacer (ITS) and nuclear large subunit (nLSU) gene regions were amplified with the primer pairs ITS5/ITS4 (White et al., 1990) and LR0R/LR7 (Vilgalys and Hester, 1990), respectively. The PCR procedure for ITS was initial denaturation at 95°C for 3 min, followed by 35 cycles at 94°C for 40 s, 54°C for 45 s, 72°C for 1 min, and a final extension of 72°C for 10 min, while that for nLSU was initial denaturation at 94°C for 1 min, followed by 34 cycles at 94°C for 30 s, 50°C for 1 min, 72°C for 1.5 min, and a final extension of 72°C for 10 min. The PCR products were purified and sequenced at the Beijing Genomics Institute (BGI), China. All the newly generated sequences were submitted to GenBank (https://www.ncbi.nlm.nih.gov/genbank/).

The current dataset for phylogenetic analysis included all the main lineages in Auriculariales as ingroup taxa, while Sistotrema brinkmannii was selected as an outgroup taxon following a study by Li et al. (2022b). The ITS and nLSU regions were separately aligned using MAFFT version 7.110 (Katoh and Standley, 2013) with the G-INS-i strategy (Katoh et al., 2005), and then the two resulting alignments were concatenated as a single alignment. The concatenated alignment was submitted to TreeBASE (http://www.treebase.org; accession number S29452). jModelTest 2.1.10 (Guindon and Gascuel, 2003; Darriba et al., 2012) was used to determine the best-fit evolutionary model of the concatenated alignment based on the Akaike information criterion (AIC). Following the resulting model, maximum likelihood (ML) and Bayesian inference (BI) analyses were performed. For the ML analysis, raxmlGUI 2.0 (Stamatakis, 2014; Edler et al., 2021) was used with the calculation of bootstrap (BS) replicates under the auto fiber channel (FC) option (Pattengale et al., 2009). For the BI analysis, MrBayes 3.2 (Ronquist et al., 2012) was used with two independent runs of four chains, and trees were sampled every 1,000th generation. The first 25% of the resulting trees were discarded as burn-in, while the remaining 75% of the resulting trees were used for constructing a 50% majority consensus tree and calculating Bayesian posterior probabilities (BPPs). Chain convergence was determined using Tracer 1.7 (Rambaut et al., 2018). The trees were visualized in FigTree 1.4.4 (Rambaut, 2018) and edited in Adobe Illustrator cc 2020.

Alloexidiopsis L.W. Zhou & S.L. Liu, gen. nov.

MycoBank: MB 844125.

Etymology: Alloexidiopsis (Latin), refers to the segregation from Exidiopsis.

Diagnosis: It differs from Exidiopsis in the combination of resupinate, leathery basidiomes and the presence of cystidia and hyphidia.

Type species: Alloexidiopsis schistacea S.L. Liu, Z.Q. Shen & L.W. Zhou (described below).

Type specimen: China: Sichuan, Pingshan County, Laojunshan National Nature Reserve, on the fallen angiosperm trunk, 19 August 2020, LW Zhou, LWZ 20200819-21a (holotype in HMAS).

Description: Basidiomes annual, resupinate, effused, thin, leathery, closely adnate. Hymenophore smooth or with sterile spines, greyish white to ochraceous, cracked or not. Hyphal system monomitic, generative hyphae with clamp connections, hyaline, thin-walled. Cystidia cylindrical to clavate, thin-walled. Hyphidia abundant, covering hymenium, branched, thin-walled. Basidia ellipsoid to ovoid, longitudinally septate, two- to four-celled, hyaline. Basidiospores cylindrical to broadly cylindrical, slightly curved (allantoid), hyaline, thin-walled, smooth, inamyloid, indextrinoid, acyanophilous. On wood.

Notes: Alloexidiopsis is characterized by grayish-white to ochraceous, corticioid basidiomes, a monomitic hyphal system, and the presence of cystidia and hyphidia. Besides Exidiopsis as indicated in diagnosis, this new genus is also close to Crystallodon and Heteroradulum in morphology. However, Crystallodon differs in the presence of hyphal pegs surrounded by crystals (Alvarenga and Gibertoni, 2021), while Heteroradulum has brightly colored (pinkish or reddish) basidiomes and a mono- or dimitic hyphal system with thick-walled generative hyphae (Malysheva and Spirin, 2017; Li et al., 2022b). The main taxonomic morphological differences among Alloexidiopsis and related corticioid genera in Auriculariales are summarized in Table 2.

Alloexidiopsis australiensis S.L. Liu, Z.Q. Shen & L.W. Zhou, sp. nov. (Figures 2A,B, 3).

MycoBank: MB 844126.

Etymology: australiensis (Latin), refers to Australia.

Diagnosis: It is characterized by smooth, cream hymenophore.

Type: Australia: Tasmania, Hobart, and Mount Wellington, on the fallen angiosperm branch, 13 May 2018, LW Zhou, LWZ 20180513-22 (holotype in MEL, isotype in HMAS).

Description: Basidiomes annual, resupinate, membranaceous, becoming leathery upon drying, closely adnate, widely effused, up to 12 cm long, 2 cm wide, 100–200 μm thick. Hymenophore smooth, cream to pale orange when fresh, becoming white upon drying. Margin gradually thinning out, thin, concolorous with or slightly darker than subiculum.

Hyphal system monomitic; generative hyphae with clamp connections. Subiculum composed of crystal clusters and agglutinated hyphae; subicular hyphae hyaline, thin-walled, frequently branched, closely interwoven, 1–2 μm in diam. Cystidia cylindrical with an obtuse apex, ventricose, 21.5–24.5 × 9.5–12 μm, with a clamp connection at base. Hyphidia arising from hyphae, nodulose or richly branched, hyaline, thin-walled, 22–33 × 1–2 μm. Basidia ellipsoid to ovoid, longitudinally septate, four-celled, embedded, 18–21 μ 13–18 μm, occasionally with a short base stalk, with a clamp connection at base. Basidiospores cylindrical to broadly cylindrical, slightly curved (allantoid), hyaline, thin-walled, smooth, acyanophilous, inamyloid, indextrinoid, with oily inclusions, (12−)13–25(−25.5) × (6.5−)7–11(−12) μm, L = 20.0 μm, W = 9.0 μm, Q = 2.3 (n = 60/2).

Other specimens (paratype) are also examined: Australia: Timbs Track, on dead standing angiosperm, 14 May 2018, LW Zhou, LWZ 20180514-18 (HMAS).

Notes: Alloexidiopsis australiensis resembles A. calcea and A. nivea (both transferred below) by smooth hymenophore in Alloexidiopsis. However, A. calcea differs in grayish-white to ochraceous hymenophore when fresh and has a distribution in the Northern Hemisphere (Wells, 1961), while A. nivea differs in smaller basidiospores (6.5–13.5 × 2.7–5.5 μm; Li et al., 2022a). Exidiopsis macrospora is similar to A. australiensis by the leathery basidiomes and the presence of cystidia and hyphidia; however, it differs in the reflexed basidiomes when dry and smaller basidiospores (10–15 μm × 5–7.5 μm; Wells, 1961).

Alloexidiopsis calcea (Pers.) L.W. Zhou & S.L. Liu, comb. nov. (Figures 2C,D).

MycoBank: MB 844128.

Basionym: Thelephora calcea Pers., Syn. meth. fung. (Göttingen) 2:581 (1801).

≡ Auricularia calcea (Pers.) Mérat, Nouv. Fl. Environs Paris, Edn 2 1:35 (1821).

≡ Corticium calceum (Pers.) Fr., Epicr. syst. mycol. (Upsaliae): 562 (1838) (1836–1838).

≡ Terana calcea (Pers.) Kuntze, Revis. gen. pl. (Leipzig) 2:872 (1891).

≡ Sebacina calcea (Pers.) Bres., Fung. trident. 2(11–13):64 (1892).

≡ Exidiopsis calcea (Pers.) K. Wells, Mycologia 53(4):348 (1962) (1961).

Notes: Alloexidiopsis calcea has been successively placed in several genera. Before the current study, its latest generic placement was Exidiopsis, which is accepted by the first and also the only comprehensively phylogenetic analyses of Auriculariales (Weiß and Oberwinkler, 2001). The phylogeny in Malysheva and Spirin (2017) recognized that Exidiopsis calcea was separated from the generic type E. effusa, but no taxonomic change was proposed may be due to a lack of specimens for careful morphological examinations. Here, five additional specimens were collected from Northwest and Southwest China grouped with E. calcea represented by the German collection of molecular weight (MW) 331 (BS = 94%, BPP = 1; Figure 1). Moreover, the morphological characters of these Chinese specimens are consistent with the description of E. calcea (Wells, 1961). Taking E. calcea falling within the clade of the newly erected genus into consideration together, this species is transferred to Alloexidiopsis.

Alloexidiopsis nivea (J.J. Li & C.L. Zhao) L.W. Zhou & S.L. Liu, comb. nov.

MycoBank: MB 844129.

Basionym: Heteroradulum niveum J.J. Li & C.L. Zhao, in Li, Zhao, and Liu, Diversity 14 (1, no. 40):5 (2022).

Notes: Alloexidiopsis nivea was recently described as a member of Heteroradulum (Li et al., 2022a). When the independence of this species was phylogenetically supported, its relationship with additional species of Heteroradulum, however, failed to receive reliable statistical support in the original phylogeny with a sampling on Auriculariaceae (Figure 1 in Li et al., 2022a). Although the original phylogeny with a narrower sampling focusing mainly on Heteroradulum did not reject the close relationship of H. niveum with other species of Heteroradulum, the practice for this phylogenetic analysis (lack of additional in-group taxa for reference) cannot accurately determine the monophyly of Heteroradulum and, thus, the phylogenetic position of H. niveum (Figure 2 in Li et al., 2022a). Including a broader sampling of reference sequences, the current phylogeny unambiguously recovers this species in the newly erected genus Alloexidiopsis (Figure 1), so we formally propose the transfer here.

Alloexidiopsis schistacea L.W. Zhou & S.L. Liu, sp. nov. (Figures 2E,F, 4).

MycoBank: MB 844127.

Etymology: schistacea (Latin), refers to the slate-like color (grayish) of hymenophore.

Diagnosis: Characterized by grayish hymenophore with small tubercles.

Type: China: Sichuan, Pingshan County, Laojunshan National Nature Reserve, on the fallen angiosperm trunk, 19 Aug 2020, LW Zhou, LWZ 20200819-21a (holotype in HMAS).

Description: Basidiomes annual, resupinate, membranaceous, becoming leathery upon drying, closely adnate, widely effused, up to 15 cm long, 2.5 cm wide, about 200 μm thick. Hymenophore smooth, covered by regularly arranged sterile spines, greyish when fresh. Margin gradually thinning out, thin, concolorous with or slightly darker than subiculum.

Hyphal system monomitic; generative hyphae with clamp connections. Subiculum composed of crystal clusters and agglutinated hyphae; subicular hyphae hyaline, thin-walled, frequently branched, closely interwoven, 2–3 μm in diam. Cystidia cylindrical with an obtuse apex, 25–50 × 4–6 μm, with a clamp connection at base. Hyphidia arising from hyphae, nodulose or branched, hyaline, thin-walled, 20–40 × 1.5–3 μm. Basidia ellipsoid to ovoid, longitudinally septate, four-celled, embedded, 15–20 × 7–10 μm. Basidiospores cylindrical to broadly cylindrical, slightly curved (allantoid), hyaline, thin-walled, smooth, acyanophilous, inamyloid, indextrinoid, with oily inclusions, (8.5−)9.5–11(−12.5) × (4.3−)4.5–5.5 μm, L = 10.4 μm, W = 5.0 μm, Q = 2.1 (n = 30/1).

Notes: Alloexidiopsis schistacea resembles Alloexidiopsis yunnanensis (transferred below) by grayish, grandinioid to odontioid hymenophore; however, the latter species differs in two- to three-celled basidia and larger basidiospores (17–24 μm × 5–8 μm; Guan et al., 2020). Micromorphologically, Exidiopsis badia and E. umbrina resemble A. schistacea by the presence of cystidia and hyphidia; however, these two species produce gelatinous, but not leathery basidiomes (Roberts, 2003). Moreover, E. badia has larger basidiospores than A. schistacea (13–15 μm × 5.5–6 μm; Roberts, 2003). Although only one collection is available for A. schistacea, its distinct morphological characters and phylogenetic position make the large enough basidiomes suitable to be described as a new species.

Alloexidiopsis yunnanensis (C.L. Zhao) L.W. Zhou & S.L. Liu, comb. nov.

MycoBank: MB 844130.

Basionym: Heteroradulum yunnanense C.L. Zhao (as “yunnanensis”), in Guan, Liu, Zhao and Zhao, Phytotaxa 437(2):57 (2020).

Notes: Alloexidiopsis yunnanensis was originally described in Yunnan, China as a member of Heteroradulum (Guan et al., 2020). However, the generic placement of this species is inaccurate as indicated in a study by Li et al. (2022b), who, thus, excluded it from Heteroradulum and left its generic position open. The current phylogeny recovers this species in the newly erected genus Alloexidiopsis (Figure 1), so we formally propose the taxonomic transfer here.