Oxneriaria nigrodisca Usman & Khalid sp. nov.

Index Fungorum number: IF 901378; Mycobank number: MB 901378; Facesoffungi number: FoF 15095; Fig. 1

Etymology – The specific epithet nigrodisca refers to the black disc of apothecia.

Holotype – LAH37201

The most important features of Oxneriaria nigrodisca are epruinose thallus, indeterminate margins, bullate to angular apothecia with black disc, narrowly ellipsoid simple ascospores, bacillus conidia, hymenium initially bright orange then turns dark orange after lugol solution, atranorin and Norstictic acid detected. Thallus crustose, epilithic, areolate, epruinose, 0.3–1.5 mm in diam., indeterminate, no distinct margins, irregular 2–5 cm across, effuse, sterile areoles clay grey, fertile areoles pale grey. Prothallus white. Thallus heteromerous, upper cortex paraplectenchymatous, hyaline, 30–65 µm thick, cells 5–8 µm in diam. Algal layer discontinuous, 50–109 µm thick, photobiont Trebauxia sp, coccoid cells, globose to ellipsoid, 9–21 µm in diam. Medulla and lower cortex not differentiated and consist of paraplectenchymatous up to 150 µm thick, globose hyaline cells, 3–6 µm diam. Apothecia: scattered, without stipe, aspicilioid, epruinose, one apothecium per areole, sometime more than one apothecium fused, bullate to angular, 400–750 mm in diam, with black disc 300–550 mm in diam, dull, concave, often with depressions. Proper exciple 16–25 µm wide. Thalline exciple 109–130 µm wide. Epihymenium brown, 10–20 µm thick. Hymenium hyaline, 78–100 µm thick. Subhymenium hyaline, 30–50 µm thick. Hypothecium hyaline, 41–60 µm thick. Asci clavate, 8–spored, 52–71×16–23 µm (x̄=61.5×19.5 μm, n=50). Ascospores simple, hyaline, narrowly ellipsoid, 13–20 × 7–10 µm (x̄=16.5 × 8.5 μm, n=20). Paraphyses propsoplectanchymatus type elongated hyphae, septate, long and short cells, short cylindrical cells 3–7×1.5–2 µm (x̄=5×1.75 μm, n=20)., with light brown terminal cell. Pycnidia lobaria type, globose to subglobose, 70–120 µm, dark brown ostiole, bacillus conidia, 2.8–3.1×1 µm (x̄=2.95×1 μm, n=30). hyaline.

Chemistry – K+ve turns orangish red, C+ve turns light green, KC+ve turns from orangish red to light orange red, UV+ve turns light green, hymenium initially bright orange then turns dark orange after lugol solution. Atranorin and Norstictic acid detected by TLC.

Ecology – Saxicolous, grows with other lichens.

Material examined – Pakistan. Gilgit Baltistan: Deosai National Park, (35° 0′ 30.21″ N, 75° 12′ 29.51″ E, 4,180 m a.s.l., on rocks, 13 May 2019, M. Usman DEO222 (LAH, holotype; LAH37201), Kharmang district, near Manthokha Waterfall, 35° 4′ 11.51″ N, 75° 59′ 47.89″ E, 2,450 m a.s.l., on rocks, 15 May 2019, M. Usman MAN21 (Paratype; LAH37416).

GenBank numbers – ITS: OR760502 (holotype), OR760503 (paratype).

Notes: – Phylogenetically, the closest species to Oxneriaria nigrodisca is O. verruculosa forming a separate branch with a 100% bootstrap value. Phenotypically, it also resembles the same taxon by having areolate grey thallus, convex apothecia, 8-spored asci and ellipsoid ascospores. However, O. nigrodisca significantly differs from O. verruculosa in having epruinose thallus (vs. pruinose thallus), indeterminate margins with white prothallus (vs. subplacodioid margins with black prothallus), larger apothecia up to 0.75 mm wide. (vs. smaller apothecia up to 0.5 mm wide), epithecium brown (vs. brownish green to olive), hymenium I+orangish red (vs. I+blue), bacillus conidia 2.8–3.1 × 1 µm (vs. thread-like, straight conidia 16–20 × c. 0.5 µm) and thallus K + orangish red (vs. K +yellow turning red) (Nimis 2016). Furthermore, phylogenetic analyses indicate that O. nigrodisca forms a separate lineage in the clade with high statistical support (100ML). To provide the recommendation to justify our new species, we follow Haji-Moniri et al. (2017), Iqbal et al. (2023) and Zulfiqar et al. (2023). A comparison of 472 nucleotides of the ITS sequences between Oxneriaria nigrodisca (LAH37201) and O. verruculosa (EU057940) reveals 26 substitutions (5.5% nucleotide differences), which we believe should be sufficient to delineate our new species.

Figure 1 – Oxneriaria nigrodisca (LAH37201, holotype). a Fertile areoles with apothecia. b Sterile areoles with pycnidia. c Section of thallus. d Section of apothecium in lugol solution. e Pycnidia. f. Conidia. Scale bars: a–b=1 mm, c=50 µm, d=200 µm, e=50 µm, f=10 µm