Lijiangomyces laojunensis gen. et sp. nov. and Sclerococcum stictae sp. nov. are reported from China and identified through DNA sequence analyses (LSU, ITS, and tef1-α) and morphological characteristics. Phylogenetic analysis showed that L. laojunensis forms a distinct lineage within Mytilinidiaceae, closely related to the Mytilinidion subclade, leading to the establishment of a new genus within this family. This saprotrophic species grows on the bark of Abies fabri, often surrounded by the thallus of Pertusaria species. Lijiangomyces laojunensis is characterized by broadly open, black hysterothecia, clavate asci, and uniseriate, hyaline muriform ascospores. Sclerococcum stictae, a new lichenicolous species, forms a sister clade relationship to a lichenicolous fungus, S. ricasoliae. It was found on the thallus of Sticta, and is characterized by black apothecia, elongate, cylindrical asci, and brown, elliptical, and 1-septate ascospores. Descriptions, illustrations, and phylogenetic analysis results of the new taxa are provided.

2 new taxa, lichen, morphology, phylogeny, saprobe, taxonomy

Mytilinidiaceae belongs to Mytilinidiales, Dothideomycetes (Hyde et al. 2024), and was introduced by Kirschstein (1924) to accommodate four genera that were originally classified under Hysteriaceae. Boehm et al. (2009a) introduced Mytilinidiales based on multigene phylogenetic analysis to accommodate Mytilinidiaceae. Pem et al. (2024) included eight genera within Mytilinidiaceae: Actidium, Lophium, Mytilinidion, Ostreola, Peyronelia, Pseudocamaropycnis, Quasiconcha and Zoggium. Hyde et al. (2024) added three more genera: Bullatosporium, Camaroglobulus and Halokirschsteiniothelia, increasing the total to eleven genera within this family. Members of Mytilinidiaceae are distinguished by their globose or obovoid pseudothecia which are typically oyster- or hatchet-shaped with a longitudinal keel and crested apex. They feature bitunicate asci containing eight ascospores that are arranged uniseriately, biseriately, or in aggregated clusters. The ascospores are hyaline to brown, exhibiting diverse morphologies such as scolecospores, didymospores, phragmospores, or dictyospores, and with bipolar symmetry (Boehm et al. 2009a).

Mytilinidion was established to accommodate the type species M. aggregatum. This genus is characterized by globoid to obovoid, erect, conchate, or dolabrate ascomata, and a thin-walled and peridium, bitunicate, 8-spored asci. The ascospores are hyaline to brown and transversely 3–5(–7)-septate (Boehm et al. 2009b; Jayasiri et al. 2018). Ostreola was introduced to accommodate two species, O. consociate and O. sessilis, characterized by conchiform to hatchet-shaped hysterothecia with a longitudinal slit that opens narrowly. The asci are cylindrical, containing eight uniseriate, brown and muriform ascospores (Darker 1963). Ostreola shares similarities with Mytilinidion and Lophium in the ascomatal morphology but is distinguished by the presence of muriform ascospores. Lumbsch and Huhndorf (2007) placed Ostreola within Mytilinidiaceae. The members of Mytilinidion are primarily saprobic and plant pathogens, while Ostreola species are primarily saprobic.

Sclerococcum belongs to Dactylosporaceae, Sclerococcales, Eurotiomycetes (Hyde et al. 2024), and was described by Fries (1819, 1825) to accommodate the parasitic hyphomycetous fungus S. sphaerale, which was previously classified as Spiloma sphaerale. Phylogenetic analysis by Diederich et al. (2013) revealed that S. sphaerale clusters with two species of Dactylospora. In a subsequent study incorporating expanded molecular data, Diederich et al. (2018) proposed adopting the family name Dactylosporaceae, with Sclerococcaceae as its synonym. They further recommended retaining Sclerococcum as the valid genus name and synonymizing Dactylospora under it, as Sclerococcum has nomenclatural priority over Dactylospora. Consequently, 46 Dactylospora species were transferred to Sclerococcum (Diederich et al. 2018). Dactylosporaceae comprises six genera: Cylindroconidiis, Fusichalara, Gamsomyces, Pseudosclerococcum, Rhopalophora and Sclerococcum (Hyde et al. 2024).

During a survey of microfungi in Yunnan Province (Thiyagaraja et al. 2024), two unidentified fungal specimens were collected. The first specimen was found on the bark of Abies fabri, and was often surrounded by the thallus of Pertusaria species while the second was observed growing on the thallus of a foliose lichen belonging to Sticta. Phylogenetic analyses and morphological comparison reveal that the first specimen represents a novel genus closely related to Mytilinidion within Mytilinidiaceae. The second specimen is proposed as a new lichenicolous species within the genus Sclerococcum based on morpho-molecular analyses.

In the analysis of Mytilinidiales, the final dataset comprised 116 taxa (Table 1) with 2246 aligned characters, including gaps (ITS 1–494 bp, LSU 495–1346 bp, and tef1-α 1347–2246 bp). The best-fit models for each gene, determined using the Bayesian information criterion (BIC), were as follows: ITS: SYM+I+G4, LSU: TN+F+R4, and tef1-α: TN+F+I+G4. For the combined dataset (LSU, ITS, and tef1-α), the parameters of the GTRGAMMA model were as follows: estimated base frequencies: A = 0.24, C = 0.25, G = 0.28, T = 0.23; substitution rate: AC = 1.12, AG = 3.35, AT = 1.77, CG = 0.88, CT = 8.54, GT = 1.00; gamma distribution shape parameter (α) = 0.325118; and tree-length = 6.868758. The best-scoring RAxML tree was constructed with a final maximum likelihood (ML) optimization likelihood value of -34,803.39. Bayesian posterior probabilities (BYPP) were calculated using MCMC analysis, achieving a final average standard deviation of split frequencies of 0.009998. The final tree topologies of ML and BYPP analyses were consistent. The best-scoring RAxML tree, based on combined LSU, ITS, and tef1-α sequence datasets, is presented in Fig. 1.

Figure 1. 

RAxML analysis of Mytilinidiales based on the combined LSU, ITS, and tef1-α sequence data. Bootstrap support values for maximum likelihood (ML ≥ 70%), and the Bayesian Posterior Probabilities (PP ≥ 0.90) are shown near the nodes as ML/PP. Orbilia auricolor (AFTOL-ID 906) and O. vinosa (AFTOL-ID 905) were used as outgroups. The newly generated sequence is in red bold font.

The resulting phylogram distinguishes eight order-level clades, most of which are well-supported, except for the Patellariales clade. Seven genera form a strongly supported Mytilinidiales clade, with Mytilinidion appearing polyphyletic. The newly identified species clusters within the Mytilinidiales clade are closely related to a Mytilinidion subclade containing eight species. The remaining Mytilinidion species form a separate clade alongside Lophium. Halokirschsteiniothelia and Quasiconcha form a sister clade to the Ostreola-Mytilinidion grouping. Additionally, two Bullatosporium strains form a distinct clade closely related to other genera within the Mytilinidiales order.

In the analysis of Dactylosporaceae, the final dataset comprised 62 taxa (Table 2) with 2041 aligned characters, including gaps (ITS 1–455 bp, LSU 456–1310 bp, and mtSSU 1311–2041 bp). The best-fit nucleotide substitution models, selected based on the Bayesian information criterion (BIC), were as follows: ITS: TIM2e+I+G4, LSU: TNe+I+G4, mtSSU: TVM+F+I+G4. The parameters for the GTRGAMMA model of the combined LSU, ITS, and mtSSU were as follows: estimated base frequencies: A = 0.29, C = 0.19, G = 0.25, T = 0.26, and substitution rate AC = 1.01, AG = 2.68, AT = 1.67, CG = 0.85, CT = 5.43, and GT = 1.00. Gamma distribution shape parameter α = 0.256278, and the tree length = 2.405501. The best-scoring RAxML tree was constructed with a final ML optimization likelihood value of - 14773.67. The final tree topologies of ML and BYPP analyses were consistent. The best-scoring RAxML tree, based on combined LSU, ITS, and mtSSU sequence datasets, is presented in Fig. 2. The newly collected specimen clusters within the Sclerococcum clade and is closely related to S. ricasoliae.

Figure 2. 

RAxML analysis of Dactylosporaceae based on the combined LSU, ITS and mtSSU sequence data. Bootstrap support values for maximum likelihood (ML ≥ 70%), and the Bayesian Posterior Probabilities (PP ≥ 0.90) are shown near the nodes as ML/PP. Caliciopsis orientalis (CBS 138.64) and Caliciopsis pinea (AFTOL-ID 1869) were used as outgroups. The newly generated sequence is in red bold font.

Taxonomy

 Lijiangomyces Meng & Jayaward., gen. nov.

Index Fungorum: IF903174

Facesoffungi Number: FoF17069

Etymology.

The genus name “Lijiangomyces” refers to “Lijiang”, the city in Yunnan Province of China from where the holotype was collected.

Description.

Sexual morph: Ascomata hysterothecia, superficial, solitary, dispersed, sessile, obovoid to broadly shell-shaped or irregularly rounded, with a broadly open or slit-like disc. Margin black, vertically erect, fragile, with the disc surface appearing yellowish-brown. Peridium carbonaceous, black in the lateral and upper regions. Hymenium hyaline to slightly yellowish, with a densely packed hamathecium. Paraphyses filiform, hyaline, non-anastomosed, and non-septate. Hypothecium slightly yellowish. Asci bitunicate, 8-spored, elongated to clavate, with a rounded apex lacking ascal wall thickening, I-, K-. Ascospores uniseriate, arranged obliquely and parallelly, hyaline, thin-walled, smooth, fusiform to ellipsoidal, K-, I+ dark blue, aseptate at immature, becoming muriform at maturity with 4–7 transverse septa and 1–2 longitudinal septa. Asexual morph: Not observed.

Type species.

Lijiangomyces laojunensis Meng & Jayaward.

Notes.

The genus is distinguished by black, broadly shell-shaped to irregularly rounded hysterothecial ascomata, with a broadly open or occasionally closed disc, typically light brown to flesh-yellow. Asci are elongated to clavate, containing eight uniseriate, hyaline, and muriform ascospores. Phylogenetic analysis places this genus within the family Mytilinidiaceae (Mytilinidiales, Dothideomycetes) closely related to Mytilinidion. In the single-gene phylogenies, the new species is positioned outside the Mytilinidia sensu stricto clade in the ITS and LSU trees but clusters within it in the tef1-α tree. However, in the concatenated analysis combining all three genes, it is again placed outside the Mytilinidia sensu stricto clade. These results support its recognition as a distinct lineage within Mytilinidiaceae. Morphologically, this genus differs significantly from Mytilinidion in having obovoid to broadly shell-shaped or irregularly rounded, with broadly open ascomata (vs. globoid to obovoid, conchate, or dolabrate ascomata with narrow slit-like openings) and hyaline and muriform ascospores (vs. hyaline to brown and transverse septa). In addition, this genus shares similar morphology with Ostreola in having muriform ascospores but differs in the broadly shell-shaped or irregularly rounded ascomata (vs. conchiform to hatchet-shaped), a broad disc opening (vs. narrowly slit-like), and hyaline ascospores (vs. brown).

 Lijiangomyces laojunensis Meng & Jayaward., sp. nov.

Index Fungorum: IF902457

Facesoffungi Number: FoF16265

Fig. 3

Etymology.

The species epithet “laojunensis” refers to the type locality “Laojun Mountain National Nature Reserve” in Yunnan Province of China.

Figure 3. 

Lijiangomyces laojunensis sp. nov., (KUN-L 88703) a, b habitat c–e ascomata (arrows) f–h section of ascomata in water i–k asci in water l, m asci in IKI n paraphyses in water o–u ascospores in water. Scale bars: 500 μm (e); 200 μm (f, g); 50 μm (h); 25 μm (i–n); 10 μm (o–u).

Holotype.

KUN-L 88703.

Description.

Sexual morph: Ascomata hysterothecia, (0.8–)0.88–1.05(–1.1) × (0.4–)0.47–0.78(–0.8) mm (x– = 0.97 × 0.63, n = 10), superficial, solitary, dispersed, sessile, non-stromatic, obovoid to broadly shell-shaped or irregularly rounded, with a broadly open or slit-like disc. Margin black, vertically erect, fragile, with a yellowish-brown, slightly depressed disc surface appearing below the rim of the lateral wall. Peridium 70–100 μm thick, carbonaceous, black laterally and apically, transitioning to grayish near the base. Hymenium 350–400 μm high, hyaline to slightly yellowish, densely packed with hamathecium. Paraphyses 1–2 μm wide, unbranched, hyaline, non-anastomosed, non-septate. Hypothecium 35–50 μm thick, slightly yellowish. Asci (120–)122.6–168.7(–190) × (13–)13.4–16.5(–18) μm (x– = 145.7 × 14.9, n = 10), bitunicate, 8-spored, elongated to clavate, rounded apex, without apical thickening of ascal wall, K-, I-. Ascospores (20–)20.9–28.8(–37.5) × (9–)10.1–15.4(–17.5) (x– = 24.8 × 12.8, n = 30) μm, K-, I+ reddish brown, then turning to dark blue, uniseriate, arranged obliquely and parallelly, hyaline, thin-walled, smooth, fusiform to ellipsoidal, aseptate at immature, becoming muriform at maturity with 4–7 transverse septa and 1–2 longitudinal septa, sometimes slightly constricted at the median septum, rounded at the ends in aged ascospores. Asexual morph: Not observed.

Material examined.

China • Yunnan Province, Lijiang City, Laojun Mountain National Nature Reserve, 26°39'N, 99°43'E, 3900 m elev., on the bark of Abies fabri (Pinaceae), 10 Apr 2022, Qing-feng Meng, ljs-52 (holotype KUN-L 88703).

Notes.

Lijiangomyces laojunensis closely resembles Ostreola consociata (the type species of Ostreola) and O. sessilis, in having cylindrical asci and uniseriate muriform ascospores. However, the new species is distinguished by its ascomatal morphology, which is broadly shell-shaped or irregularly rounded with a widely opened disc, in contrast to Ostreola species which have conchiform to hatchet-shaped ascomata with a narrow slit-like opening. Furthermore, the ascospores of the new species are hyaline and larger in size (20.9–28.8 × 10.1–15.4 μm), in contrast, brown and smaller ascospores (14–22 × 6–8 μm) are the characteristic feature of Ostreola (Darker 1963).

Phylogenetic analysis places this species as a sister clade to Mytilinidion, however, it can be distinguished by its obovoid to broadly shell-shaped or irregularly rounded ascomata (vs. globoid to obovoid, erect, conchate, or dolabrate), and hyaline and muriform ascospores (vs. hyaline to dark brown and transversely septate) (Boehm et al. 2009b; Jayasiri et al. 2018).

 Sclerococcum stictae Meng, Diederich & Thiyagaraja, sp. nov.

Index Fungorum: IF903175

Facesoffungi Number: FoF17070

Fig. 4

Etymology.

The species epithet “stictae” refers to “Sticta”, the host lichen on which the holotype was found.

Figure 4. 

Sclerococcum stictae sp. nov., growing on the thallus of Sticta sp. (KUN-L 88687) a, b habitat and appearance of the host lichen c, d appearance of the apothecia e, f section of apothecium in water g immature ascus in water h mature ascus with ascospores in water i asci in I j–o ascospores in water. Scale bars: 1 mm (c); 200 μm (d); 100 μm (e); 50 μm (f); 10 μm (g–i); 5 μm (j–o).

Holotype.

KUN-L 88687.

Description.

Sexual morph: Ascomata apothecioid, 200–300 μm in diam., rounded, cup-shaped, sessile, erumpent from the host thallus with a narrow base, 170–200 μm in diam., either dispersed or occurring in small groups, black, matte. Disc flat, black. Margin distinct, persistent, and concolorous with the disc. Exciple brown, paraplectenchymatous, laterally 40–70 μm wide. Epithecium (12–)14.3–21.0(–24) μm thick (x– = 17.7, n = 30), with dark brownish granules. Hymenium (46–)65.2–94.8(–96) μm high (x– = 80, n = 30), light brown, and distinctly gelatinized, K/I+ reddish with bluish in epihymenium. Paraphyses 2–3 μm wide, anastomosing, branched, septate, with swollen, pigmented apices. Hypothecium (86–)89.6–95.2(–97) μm thick (x– = 92.4, n = 30), dark orange-brown, with irregularly shaped hypothecial cells. Asci (40–)44.8–67.9(–72) × (7–)7.8–11.9(–12) μm (x– = 56.3 × 9.9, n = 10), bitunicate, narrowly clavate to cylindrical, ascus wall thickened at the apex, ocular chamber absent, 8-spored, K/I-, except for the K/I+ blue outer gelatinous coat, most intensely colored around the ascus apex. Ascospores (8–)9.2–11.1(–12) × (5–)5.1–6.2(–7) μm (x– = 10.1 × 5.6, n = 30), l/w ratio = (1.5–)1.7–1.9(–2) (x– = 1.8, n = 30), brown when mature, 1-septate, slightly constricted at the septum, verrucose, slightly asymmetric with a larger upper cell, ellipsoidal, sometimes soleiform. Asexual morph: Not observed.

Material examined.

China • Yunnan Province, Diqing Autonomous Prefecture, Meili Mountain National Nature Reserve, 28°24'N, 98°48'E, 3300 m elev., on the thallus of Sticta sp., on the bark of Rhododendron lapponicum (Ericaceae), 21 Apr 2023, Qing-feng Meng, ml-68 (holotype KUN-L 88687).

Notes.

Sclerococcum stictae clusters within a well-supported subclade along with S. ricasoliae and S. lobariellum. The basepair comparison with S. ricasoliae revealed 7.5% differences (34/455 bp) in ITS, 2.2% (19/855 bp) differences in LSU, and 1% (7/730 bp) differences in mtSSU sequences (Flakus et al. 2019). Compared to S. lobariellum, it exhibits 4.21% differences (36/855 bp) in LSU and 1.1% (8/730) in mtSSU. Morphologically, S. stictae resembles S. ricasoliae in its ascomatal and ascospore appearance but can be distinguished by its longer, narrower asci (c. 45–68 × 8–12 μm vs. 35–50 × 10–15 μm) and broader ascospores (c. 9–11 μm vs 4–6 μm), with a smaller length/width ratio (1.7–1.9 vs. 1.5–3.5) (Flakus et al. 2019). Phylogenetically, S. stictae is also related to S. lobariellum, but the basepair comparison revealed 4.3% (37/855 bp) differences in LSU and 1.1% (8/730 bp) differences in mtSSU sequences (Hafellner 1979). Hence based on recommendations outlined by Jeewon and Hyde (2016), the establishment of the new species is supported. Diederich et al. (2024) have shown that both Sclerococcum lobariellum and S. ricasoliae possess an asexual stage producing dark brown, dispersed, muriform conidia, often co-occurring with the sexual stage. In all other known lichenicolous Sclerococcum species with an asexual stage, conidia are produced within compact sporodochia, and this stage is never accompanied by a sexual stage. We anticipate, therefore, that an asexual stage with dispersed, muriform conidia also exists in the new S. stictae and should be searched for when more specimens become available.

Another species, Sclerococcum dendriscostictae, also found on Sticta, shares morphological traits with S. stictae. However, the new species can be distinguished by its longer asci (c. 45–68 × 8–12 μm vs. 33–44 × 9.5–13.5 μm) and verrucose ascospore ornamentation, in contrast to smooth-walled ascospores reported in S. dendriscostictae (Joshi 2021).

Hysteriaceous fungi are distinguished by their persistent, carbonaceous, navicular pseudothecia with a longitudinal slit opening. Historically, the mytilinidiaceous fungi, which possess fragile, shell-shaped pseudothecia that dehisce through a longitudinal cristate apex, were considered part of the hysteriaceous. However, Boehm et al. (2009a, 2009b) reclassified these fungi based on phylogenetic analyses, leading to the establishment of the order Mytilinidiales.

In our phylogenetic analysis, six genera within Mytilinidiales form a distinct yet complex clade. Mytilinidion is split into two subclades, indicating its polyphyletic nature. This is consistent with the previous study by Boehm et al. (2009a). One subclade includes four species of Mytilinidion alongside all Lophium species, forming a well-supported Lophium-Mytilinidion clade. The other subclade contains eight Mytilinidion species with our new collection, although this grouping is weakly supported. Morphologically, Mytilinidion species are defined by globoid to obovoid, conchate, or dolabrate ascomata with narrow slit-like openings, bitunicate, 8-spored asci, and hyaline to dark brown ascospores with 3–5(–7) transverse septa (Boehm et al. 2009b; Jayasiri et al. 2018). However, our new species displays distinct morphological features that diverge significantly from those of Mytilinidion, supporting its exclusion from this genus based on both phylogenetic and morphological evidence.

Hyde et al. (2024) accepted one family and eleven genera within Mytilinidiales, most of which lack muriform septation except Ostreola which was introduced by Darker (1963). Although molecular evidence for Ostreola remains unavailable, our new species shares features with it, such as cylindrical asci and uniseriate muriform ascospores but differs from Ostreola in having broadly opened hysterothecia, while Ostreola exhibits narrow, slit-like openings. Additionally, Ostreola typically has dull-brown muriform spores, whereas our species is distinguished by its hyaline muriform ascospore (Harkness and Cooke 1878; Darker 1963; Tilak and Kale 1968; Rao and Modak 1972; Barr 1987).

Phylogenetic analysis further positions our new species at a significant distance from the recently described genus Bullatosporium (Andreasen et al. 2024). Apart from the six genera included in our phylogenetic analysis, four additional genera within the family, viz. Actidium, Camaroglobulus, Peyronelia, and Zoggium lack molecular data but exhibit distinct morphological characteristics. Actidium is characterized by simple, rounded spores (Fries 1815). Camaroglobulus was introduced as the asexual morph of Mytilinidion resinae, though its taxonomic placement requires further molecular confirmation (Speer 1986). Peyronelia is defined by brown, fusiform conidia that form short chains of slender, septate, interconnected cells (Ciferri and Fragoso-Romualdo 1927) and Zoggium features broadly filiform or vermiform spores that are transversely septate and pale-colored (Vasilyeva 2001).

Given these morphological and phylogenetic distinctions, the establishment of a new genus to accommodate our newly identified species is both necessary and justified. This classification will provide a clearer framework for understanding diversity within the order Mytilinidiales.

The holotype of Lijiangomyces laojunensis exhibits another intriguing feature: the base of its apothecium is surrounded by the thallus of Pertusaria sp. This phenomenon has led us to mistakenly identify it as a lichenicolous species. Although lichenicolous behavior was not confirmed in this study, the close physical association suggests that the two fungi coexist without conflict. It is also possible that lichenicolous species may be identified as more specimens are collected and studied in the future.

Before 2018, Dactylospora and Sclerococcum were considered distinct genera, with Sclerococcum containing 21 species, 19 of which were lichenicolous. Diederich et al. (2018) synonymized Dactylospora with Sclerococcum and transferred 46 species from Dactylospora to Sclerococcum. Subsequently, Olariaga et al. (2019) transferred 14 non-lichenicolous species of Dactylospora to Sclerococcum. Johnston (2022) introduced six new saprophytic species of Sclerococcum. Since 2018, ten new lichenicolous species and three combinations have been added to the genus (Elix et al. 2019; Flakus et al. 2019; Fryday 2019; Navarro-Rosinés and Romero 2019; Spribille et al. 2020; Joshi 2021; Zhurbenko 2022; Paz-Bermúdez et al. 2023; Diederich et al. 2024; Zhurbenko and Diederich 2024). Diederich et al. (2024) have accepted a total of 85 species in Sclerococcum, with 64 lichenicolous species and the remainder being saprotrophs on liverworts, wood, and bark in both terrestrial and marine habitats (Dong et al. 2020; Thiyagaraja et al. 2022).

The first study of Sclerococcum in China was conducted by Thiyagaraja et al. (2022), who reported a new geographical record of S. simplex, collected from a corticolous Pertusaria thallus in Yunnan province. Ma et al. (2023) described the lignicolous asexual species, S. pseudobactrodesmium from Guizhou Province. Meng et al. (2024) reported a new geographical record of S. glaucomarioides found on Ochrolechia akagiensis from China. This study provides an additional new Sclerococcum species from China.

Qingfeng Meng thanks Thesis Writing Grant of Mae Fah Luang University, Chiang Rai, Thailand. Vinodhini Thiyagaraja thanks Chinese Research Fund (project no E1644111K1) entitled “Flexible introduction of high-level expert program, Kunming Institute of Botany, Chinese Academy of Sciences’’, Yunnan Province “Caiyun Postdoctoral Program” in 2023, Choi Wan Postdoctoral Program 2023 and National Postdoctoral funding, China. RS Jayawardena would like to thank the Eminent scholar offered by Kyun Hee University.