Oxneriaria crittendenii Usman & Khalid

Usman, Muhammad, Dyer, Paul S., Brock, Matthias, Wade, Christopher M. & Khalid, Abdul Nasir, 2024, Two novel species of arctic-alpine lichen-forming fungi (Ascomycota, Megasporaceae) from the Deosai Plains, Pakistan, MycoKeys 102, pp. 285-299 : 285

Oxneriaria crittendenii Usman & Khalid

Fig. 1

Etymology.

The specific epithet " crittendenii " refers to the British lichenologist Prof. Peter D Crittenden in recognition for his outstanding contributions to lichenology.

Holotype.

Pakistan. Gilgit Baltistan: Deosai Plains (35°0'45.73"N, 75°13'25.95"E, elev. 4,651 m) on rocks, 13 May 2019, M. Usman DEO117 (LAH, holotype; LAH37193). GenBank OR037223 [ITS], OR037219 [LSU], OR037259 [mtSSU].

Diagnosis.

It differs from its closest species O. pruinosa by having lobate black margins (vs. non-lobate), orbicular thallus 1.5-5 cm (vs. irregular 3-8 cm), K test negative (vs. K positive yellow), distinct proper-exciple 17-40 µm wide (vs. indistinct) and polarilocular ellipsoid ascospores (vs. simple ellipsoid).

Description.

Thallus crustose, epilithic, orbicular, 1.5-5 cm across, zonate, fine bullate to areolate in the centre to poorly areolate towards margin, in the centre areoles 0.5-1 mm diam. and a few areoles changing to squamules up to 1.8 mm in length, lobate at margins, determinate and radiate. Hypothallus distinct, shiny light brown. Upper surface grey with white powdery texture and black at margins. Thallus heteromerous, upper cortex 20-60 µm thick, globose to sub-globose hyaline paraplectenchymatous cells, 6-11 µm in diam. Algal layer discontinuous, 90-140 µm thick, photobiont Trebouxia sp, coccoid cells, globose to sub-globose 6-14 µm in diam. Medulla and lower cortex not differentiated and consisting of paraplectenchymatous, globose to sub-globose hyaline cells 25-45 µm in diam.

Apothecia without stipe, aspicilioid, one apothecium per areole, rounded, 600-950 µm in diam., pruinose with black disc 450-700 µm, dull and concave. Proper exciple 17-40 µm thick. Thalline exciple 140-190 µm thick. Epihymenium brown, 10-20 µm thick. Hymenium hyaline, 85-110 µm thick. Hypothecium hyaline, 35-55 µm thick. Asci clavate, 8-spored, 60-100 × 22-30 µm. Ascospores hyaline, ellipsoid, polarilocular, 13-18 × 7-11 µm. Paraphyses moniliform, septate, cylindrical cells 3-10 × 1-2.5 µm, with internally brown terminal cells. Pycnidia roccella type ( Ryan et al. 2002), globose to pyriform, 115-200 × 85-200 µm dark brown ostiole, long filiform hyaline conidia, 17-24 × 1 µm.

Ecology.

Saxicolous, calcareous, known only from Deosai Plains, Gilgit-Baltistan, occurring at elevations between 4,117 m and 4,651 m in extremely cold conditions.

Chemical study:

K -ve, C -ve, KC -ve, UV +ve (light green), hymenium initially blue then turning dark orange after Lugol’s solution. Substictic acid detected through TLC.

Additional material examined.

Pakistan. GILGIT BALTISTAN: Deosai Plains , 35°7'22.48"N, 75°36'35.09"E, elev. 4,177 m, on rocks, 3 September 2020, M. Usman & M. Shafiq DEO129 (LAH, paratype; LAH37194; GenBank OR 037224 [ITS], OR037220 [LSU], OR037260 [mtSSU].

Figures

Figure 1. Oxneriaria crittendenii sp. nov. holotype (LAH 37193) A thallus B margins C apothecia under stereomicroscope D ascospores in Lugol's solution E conidia F pycnidium. Photos by Muhammad Usman. Scale bars: 5 cm (A); 1 mm (B, C); 20 μm (D, E); 100 μm (F).