Astrothelium peudostraminicolor S.H. Jiang, C. Zhang & J.C. Wei, sp. nov.
Index Fungorum number: IF 841113; Mycobank number: MB 841113; Facesoffungi number: FoF 13377; Figs. 1, 2
Etymology – The epithet “peudostraminicolor” refers to the similarity with Astrothelium straminicolor.
Holotype – HMAS−L 151080.
Thallus crustose, corticate, olive-green to yellowish, shiny, uneven to bullate, continuous, cortex distinct, prothallus not observed, 0.2‒0.4 mm thick, covering areas up to 8 cm in diam., not inducing gall formation of the host bark. Algae trentepohlioid. Ascomata perithecia, conical or pyriform, black, 0.3‒0.7 mm in diam., erumpent, covered by thallus except for dark ostiolar area surrounded by whitish rim, solitary or aggregated in pseudostromata. Pseudostromata rounded to irregular, erumpent to prominent, covered by a thallus layer, with flattened top. Ostiole appearing as blackish dot, eccentric, fused, 30‒100 μm in diam. Ascomata Wall carbonized, black, 20‒90 μm thick. Hamathecium composed of densely anastomosing, netlike paraphyses, inspersed with oil drops. Asci cylindrical to clavate, 120–140 × 16–21 μm. Ascopores 8 per ascus, biseriate to irregular, hyaline, transversely 3-septate, 17‒30 × 6‒10 μm, fusiform, ends rounded, lumina diamond-shaped, surrounded by a smooth gelatinous sheath, 2‒8 μm wide. Pycnidia not seen.
Chemistry – Thallus UV-. Pseudostromata UV-. No substance detected by TLC.
Habitat and distribution – The new species grows on the bark of tropical and subtropical regions, and is currently only found in China.
Material examined – China, Guangxi Province, Xing’an county, Maoershan National Nature Reserve, 25° 52′ 10′′ N, 110° 24′ 47′′ E, 2025 m alt., on bark, 21 August 2017, X.L. Wei, R.D. Liu, X. Qian, Y.B. Zuo, X.M. Cheng 20191091 (HMAS−L 151080, holotype); ibid., XA2017068 (HMAS−L 0139996).
GenBank numbers – HMAS−L 151080: ITS= OM001629; HMAS−L 0139996: ITS= OM001628.
Notes – This species keys out in the recent world key (Aptroot 2021) in key K at couplet 6. It is similar to Astrothelium straminicolor, but the latter often has prominent pseudostromata, laterally covered by a thallus, with one to several groups of fused ascomata forming broad, flat, dark ostiolar areas often fused in a lobate pattern (Aptroot and Lücking 2016). Another similar species is A. pyrenastrosulphureum, but its pseudostromata are often prominent, covered by a thallus, with one to several groups of fused ascomata with dark, papilliform, always separate ostiolar areas, but without a whitish rim (Aptroot and Lücking 2016).
Figure 1 – Astrothelium peudostraminicolor (HMAS−L 151080, holotype). a Thallus with ascomata. b Pseudostromata and ostioles. c asci. d ascospores. Scale bars: a=0.1 mm, b=0.2 mm, c=20 µm, d=10 µm
Figure 2 – Phylogenetic tree showing the internal phylogeny of Astrothelium, constructed through Bayesian analysis based on ITS with an alignment length of 455 bp. Bayesian inference posterior probabilities above 95% (left) and Maximum likelihood bootstrap support above 70% (right) are shown at nodes (B–PP / ML–BP)