Sclerococcum stictae Meng, Diederich & Thiyagaraja, 2025

Meng, Qingfeng, Diederich, Paul, Thiyagaraja, Vinodhini, Ertz, Damien, Wang, Xinyu, Saichana, Natsaran, Hyde, Kevin D., S. Jayawardena, Ruvishika & Fu, Shaobin, 2025, Lijiangomyces laojunensis gen. et sp. nov. (Mytilinidiaceae), and Sclerococcum stictae (Dactylosporaceae), a new lichenicolous species from Yunnan, China, MycoKeys 114, pp. 277-298 : 277-298

Sclerococcum stictae Meng, Diederich & Thiyagaraja sp. nov.

Fig. 4

Etymology.

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

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) .

Figures

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).