Buellia subhemispherica R. Ngangom & Nayaka 2025, sp. nov.

Buellia subhemispherica R. Ngangom & Nayaka, sp. nov. MycoBank No.: MB856018 Type:— INDIA. Karnataka, Bangalore District, Bannergatta, Hazam Kallu, on siliceous rock, elev. 980 m, 30 April 1979, D.D. Awasthi, G. Awasthi, R. Mathur & P. Srivastava 79.255 (holotype LWG-LWU, isotype LWG). (Fig. 2) Thallus saxicolous, crustose, epilithic, pale grey to ivory, rimose to areolate, thin to moderately thickened upto 0.18 mm thick; prothallus visible as black margin only around thallus; medulla white, I+ blue, lacking calcium oxalate (H 2 SO 4 −). Apothecia numerous, lecideine, sessile, round, single or in groups, 0.3–0.6 mm diam., margin thick, prominent in young apothecia, becoming thinner when mature, but not excluded; disc black, flat becoming convex at maturity, epruinose; exciple dispersa - type, 40–60 µm thick, inner excipular hyphae narrow, pale brown, forming a pale middle layer, outer excipular hyphae parallel, dark brown, with aeruginose pigments (K–, HNO 3 + violet); epihymenium brown, 8–10 μm thick, K–, HNO ₃–; hymenium hyaline 40–50 µm high, not inspersed with oil droplets; paraphyses simple to moderately branched, apically swollen (3–4 µm diam.), with brown pigment cap (cf. elachista brown), aeruginose pigment absent; hypothecium dark brown, 100–130 μm high. Asci clavate, Bacidia- type, 8-spored. Ascospores 1- septate, brown at maturity, oblong to ellipsoid, usually not constricted at septum, not curved, Buellia - type, proper septum and spore wall thin, not thickening during spore ontogeny, ornamentation absent, (9.5–)10.2–12.3(–13.7) × (4.5–)5.0–5.5(–6) µm, l/w= (1.9–)2.0–2.3(–2.4) (n = 30). Pycnidia rare, subimmersed, globose, ontogeny similar to the Umbilicaria - type sensu Vobis & Hawksworth (1981); conidia simple bacilliform, 4–5 × 1–1.5 µm. Chemistry: Spot tests: K+ yellow turning red (forming crystals), P+ yellow, C−. Thallus UV +, orange. TLC: norstictic acid (major), 4,5-dichlorolichexanthone (major), connorstictic acid (minor). Etymology: The species epithet “ subhemispherica ” derives from the similar species B. hemispherica S. Singh & Awasthi. Distribution: The new species is known from the Deccan plateau region of India, characterized by dry deciduous and tropical scrub forests at an elevation of approximately 1000 m, growing on siliceous rock. Notes: Buellia subhemispherica is characterized by a rimose-areolate thallus with a smooth, pale grey to ivory surface, dispera - type exciple with aeruginose pigment, which appears masked by a brown pigment and is best seen when treated with HNO 3. The external morphology of the species resemblance Buellia hemispherica S.R. Singh & D.D. Awasthi (1981:186), however, specimen of B. hemispherica have strongly convex apothecial discs and lack aeruginose pigmentation in the exciple. Buellia subhemispherica also resembles B. quartziana S.R. Singh & D.D. Awasthi (1981:189), but the latter has dispersed areoles, an I− medulla, adnate to subsessile apothecia and larger ascospores (11–15 × 5–7 µm). Morphologically and chemically Buellia subhemispherica is also similar to B. mackeei Elix & H. Mayrhofer (2019:40), but the latter differs by an I− medulla and calcium oxalate in its medulla (H 2 SO 4 +) (Elix & Mayrhofer 2019).