Myriostigma visus-blotch J. X. Xue & Lu L. Zhang, 2025

Xue, Junxia, Yang, Zihao, Li, Ruotong & Zhang, Lulu, 2025, Four new species of Cryptothecia (Arthoniaceae, Ascomycota) and Myriostigma (Arthoniaceae, Ascomycota) from China, based on morphology and molecular phylogeny, MycoKeys 114, pp. 367-383 : 367-383

Myriostigma visus-blotch J. X. Xue & Lu L. Zhang sp. nov.

Fig. 5

Diagnosis.

The new species differs from other species of Myriostigma in ascigerous areas, which have many irregular small patches that are scattered or clustered together radially elongated; hyaline ascospores (31 –) 37–74 × (14 –) 17–29 µm.

Type.

China • Yunnan Province, Xishuangbanna Dai Nationality Autonomous Prefecture, Jinghong City, Primitive Forest Park , 22°2'9.71"N, 100°53'5.81"E, alt. 716 m, on the bark of trees, 7 March 2023, L. L. Liu et al. 20230681 ( SDNU, holotype) ; • ibid., Mengla County, Menglun Town, Xishuangbanna Tropical Botanical Garden , 21°55'12.06"N, 101°16'5.55"E, alt. 496 m, on the bark of trees, 5 March 2023, L. L. Liu et al. 20231187 ( SDNU, paratype) .

Description.

Thallus corticolous or bambusicolous, up to 6.5 cm in diameter, ecorticate, cottony, dull, pale green to greenish grey, firmly attached to the substrate. Isidia not observed. Prothallus is usually distinct, thin, whitish byssoid, mainly composed of interwoven and radiating hyphae, 0.8–2.5 mm wide, forming a dark brown to black line while bordering different species. Medulla white, with calcium oxalate crystals. Photobionts trentepohlioid, cells elliptical to oblong, single or aggregate into bundles, 6–14 × 6–9 µm. Hyphae 1–2 µm wide.

Ascigerous areas are distinct, generally delimited, slightly raised above the thallus level, developing in the thallus centre, colour lighter than the thallus, many irregular small patches that are scattered or clustered together radially elongated. Asci hyaline, globose to subglobose, often covered by hyaline hyphae, 8 - spored, 82–91 × 81–90 µm. Ascospores hyaline, oblong, muriform, curved, often broader in the centre, (31 –) 37–74 × (14 –) 17–29 µm.

Pycnidia hyaline, globose to subglobose, scattered and immersed across the thallus, 55–85 × 54–80 μm. Conidia hyaline, short bacilliform, 4–5 × 0.9–1 μm.

Chemistry.

thallus C + red, K + pale yellow, P –, UV + pale grey-white; medulla and paraphysoids I + sky-blue. TLC: gyrophoric acid, lecanoric acid and confluentic acid.

Etymology.

The epithet refers to its ascigerous areas having many irregular pale green small patches.

Ecology and distribution.

This species is found only in China on bamboo and trees in humid tropical forests in Hainan and Yunnan Provinces.

Notes.

Myriostigma visus-blotch is widely distributed in the Xishuangbanna Dai Nationality Autonomous Prefecture. The ascigerous areas of M. visus-blotch begin as a small bulge slightly higher than the thallus and gradually become multiple small patches or radially elongated in the centre of the thallus, and the colour of the ascigerous areas is pale green. In addition, we found that species with asci generally do not have pycnidia, and species with pycnidia generally do not have asci.

Phylogenetically, Myriostigma visus-blotch is clustered with M. flavescens J. X. Xue & Lu L. Zhang and M. laxipunctata J. X. Xue & Lu L. Zhang. They all have C + red thalli, globose asci and muriform ascospores, but M. flavescens has a black linear shape prothallus, white ascigerous areas and yellow ascospores (58–76 × 19–28 µm). M. laxipunctata has complete ascigerous areas (not small patches or radially elongated), larger asci (95–124 × 93–119 µm), and loose brown dots indicating asci ( Xue et al. 2024).

Additional specimens examined.

China • Hainan Province, Baoting Li and Miao Autonomous County, Qixianling Hot Spring National Forest Park , 18°42'14.43"N, 109°41'47.92"E, alt. 325 m, on the bark of trees, 8 March 2023, J. X. Xue et al. 20230142 ( SDNU) ; • ibid., 20230138 ( SDNU) ; • ibid., 20230134 ( SDNU) ; • Yunnan Province, Xishuangbanna Dai Nationality Autonomous Prefecture, Jinghong City, Mengla County, Menglun Town, Xishuangbanna Tropical Botanical Garden , 21°55'45.40"N, 101°15'29.17"E, alt. 518 m, on the bark of trees, 4 March 2023, L. L. Liu et al. 20230950 ( SDNU) ; • ibid., 20230969 ( SDNU) ; • ibid., 21°55'30.14"N, 101°15'42.72"E, alt. 527 m, on the bark of trees, 5 March 2023, L. L. Liu et al. 20233946 ( SDNU) ; • ibid., 21°55'50.99"N, 101°15'33.29"E, alt. 512 m, on the bark of trees, 4 March 2023, L. L. Liu et al. 20230973 ( SDNU) ; • ibid., 21°55'55.96"N, 101°14'35.00"E, alt. 560 m, on the bark of trees, 4 March 2023, L. L. Liu et al. 20230847 ( SDNU) ; • ibid., on bamboo, 4 March 2023, L. L. Liu et al. 20230837 ( SDNU) ; • ibid., Jinuo Mountain, Jinuo Ethnic Township , 21°54'52.26"N, 101°11'33.04"E, alt. 640 m, on the bark of trees, 3 March 2023, L. L. Liu et al. 20230502 ( SDNU) ; • ibid., Wild Elephant Valley , 22°10'37.70"N, 100°51'24.54"E, alt. 749 m, on the bark of trees, 6 March 2023, L. L. Liu et al. 20230602 ( SDNU) ; • ibid., Primitive Forest Park , 22°2'9.71"N, 100°53'5.81"E, alt. 746 m, on the bark of trees, 7 March 2023, L. L. Liu et al. 20230692 ( SDNU) .

Figures

Figure 5. Myriostigma visus-blotch (SDNU 20230950, type for (A, B); SDNU 20230681, holotype for (C, D); SDNU 20230847, type for (E, F )) A thallus and prothallus B ascigerous areas C asci D ascospores E pycnidia F conidia. Scale bars: 500 µm (A, B); 10 µm (C, D, E, F).