Lobothallia rubra Lun Wang & Y. Y. Zhang, 2025

Wang, Lun, Feng, Yi-Shan, Wang, Li-Song, Wang, Xin-Yu & Zhang, Yan-Yun, 2025, An overview of the genus Lobothallia (lichenized Ascomycota, Megasporaceae) in China, MycoKeys 125, pp. 205-244 : 205-244

Lobothallia rubra Lun Wang & Y. Y. Zhang sp. nov.

Fig. 7

Etymology.

The specific epithet refers to the red reaction of medulla in C spot-test.

Diagnosis.

Thallus areolate with a lobate margin, upper surface white with pale brown tinge, pruinose; areoles raised when bearing apothecia or pycnidia; apothecia lecanorine, disc pruinose; pycnidia protruding; medulla C + rose – red, contain gyrophoric acid.

Holotype.

China • Xinjiang Uygur Autonomous Region: Hejing Co., Baluntai Vil. , 42°51'56.45"N, 86°27'09.16"E, alt. 2026 m, on rock, 02 July 2022, Xin-Yu Wang and Min Ai XY 22-897 ( holotype: KUN-L 84715 ) .

Description.

Thallus closely adnate to substrate, up to 5 cm across, areolate, 1–4 mm thick, marginally lobate, 0.4–1 mm thick. Areoles (0.5 –) 0.8–2 (– 2.4) mm wide, contiguous, angular to rounded, non-constricted at base, interspaces between areoles 0.1–0.2 mm wide. Lobes slightly broader in the apex, 2–3 mm long, 0.7–1.4 mm wide at base, 0.6–2 (– 2.5) mm wide at apex. Upper surface convex, cracked, pruinose, white with pale brown tinge where pruina is thin. Upper cortex paraplectenchymatous, 20–40 μm thick, containing brown granules (soluble in K); epinecral layer composed of coarse plate-like crystals, gelatinous material, and gray-black granules (insoluble in K), 10–30 μm thick. Algal layer 75–150 μm high, discontinuous, interrupted by hyphae, 10–60 μm wide; photobiont chlorococcoid, cells 8–20 µm diameter. Medulla 0.5–1 mm high, filled with gray – black granules (generally insoluble in K). Lower cortex absent.

Apothecia lecanorine, common, usually 1 per areole, (0.3 –) 0.6–1.5 (– 2.0) mm diameter, rounded, sessile, slightly constricted at base when mature; disc slightly concave to plane, black, pruinose; apothecial margin entire, persistent, 0.1–0.25 mm wide, pruinose, concolorous with thallus. Exciple narrow, up to 40 μm wide. Epithecium, hymenium and subhymenial layers combined (150 –) 175–225 (– 250) µm high; epithecium 5–20 µm high; epihymenium 20–50 μm high, filled with dark brown granules (soluble in K), N –; hymenium 100–150 μm high, hyaline, I – or I + weakly bluish in lower part; subhymenial layers 50–100 μm high, hypothecium 40–50 μm, hyaline, I + blue; algal layer below hypothecium discontinuous, 50–60 μm high; paraphyses simple, septate, submoniliform at the tips, with 2–3 uppermost cells shorter and broader than basal cells, 3–6 μm wide (basal cells 2–3 μm wide); asci clavate, Aspicilia - type, hyaline, 8 - spored, 70–85 × 20–30 µm; ascospores simple, hyaline, broadly ellipsoid, (10.0 -) 11.9–13.1 – 14.2 (- 15.0) × (8.0 -) 8.7–9.4 – 10.0 (- 11.0) µm (n = 48), l / w ratio (1.0 -) 1.3–1.4 – 1.5 (- 1.8), wall ca. 1 µm thick. Pycnidia common, protruding, 0.1–0.25 mm in diameter, sometimes elongated, 0.5 (– 0.7) × 0.2 mm (length × width); ostiole brownish to dark brown; conidia bacilliform, hyaline, 5–6 × 1 µm.

Chemistry.

Cortex: K + pale yellow, P –; medulla: K + pale yellow to orange or K –, P –, C + rose – red, KC + red to pale yellow; containing gyrophoric, norstictic, stictic, connorstictic and constictic acids.

Habitat and distribution.

Saxicolous. Currently known only from Xinjiang, China.

Notes.

This species is readily recognized by its C + rose – red medullary reaction, resulting from the production of gyrophoric acid. Lobothallia semisterilis resembles this species in its white to gray thallus and protruding pycnidia, but differs in being terricolous and lacking gyrophoric and stictic acids ( Zhang et al. 2020). Lobothallia pruinosa shares the characteristic white pruina on both thallus and discs, but differs in its thinner thallus, punctiform pycnidia, and the presence of norstictic and connorstictic acids as the major secondary metabolite ( Kou et al. 2013). Lobothallia pulchra is similar to L. rubra in possessing white thallus and lecanorine apothecia, but differs in having epruinose discs and lacking gyrophoric acid.

Additional specimens examined.

China • Xinjiang Uygur Autonomous Region: Hejing Co., Baluntai Town , 42°51'56.45"N, 86°27'09.16"E, alt. 2026–2046 m, on rock, 2 July 2022, An-Cheng Yin and Han-Xiang Chen 22-72301 ( KUN-L 86927 ) • National Highway 216 , 42°51'56.39"N, 86°27'09.31"E, alt. 2100 m, on limestone, 2 July 2022, Li-Song Wang et al. 22-72886 ( KUN-L 87373 ) .

Figures

Figure 7. Lobothallia rubra (KUN-L 84715, holotype); A. Thallus; B. Apothecia; C. Pycnidia; D. Lobes; E. Section of thallus (LCB); F. Section of thallus (in K); G. Vertical section of apothecium; H. Vertical section of apothecium (LCB); I, J. Vertical section of pycnidium; K. Ascus and ascospores; L. Paraphyses (left in LCB, right in K); M. Conidia (LCB). Scale bars: 2 mm (A); 0.5 mm (D); 0.2 mm (B, C); 50 µm (G, I, J); 20 µm (E, F, H); 10 µm (K, M); 5 µm (L).