Buellia austroindica R. Ngangom, Nayaka, Mohabe & A. M. Reddy 2025, sp. nov.

Buellia austroindica R. Ngangom, Nayaka, Mohabe & A.M. Reddy, sp. nov. MycoBank No.: MB856017 Type:— INDIA. Andhra Pradesh, Chittoor district, Thamballepatti, on siliceous rock, elev. 1676 m, 05 January 2013, Satish Mohabe & A. Madhusudana Reddy 2782 (holotype LWG, isotype LWG). (Fig. 1) Thallus saxicolous, crustose, epilithic, brownish yellow, rimose to areolate, up to 0.2 mm thick, surface smooth; prothallus visible as black margin around thallus; medulla pale yellow orange, I+ blue, lacking calcium oxalate (H 2 SO 4 −). Apothecia numerous, lecideine, initially adnate, soon becoming sessile, round, single (less often in groups), 0.3– 0.6 mm diam.; margin black, thick and distinct, reduced with age but persistent, covered with irregular thalline collar concolorous with the thallus, prominent only in younger apothecia, becoming dark brown to black at maturity; disc black, flat, becoming slightly convex when mature, finely covered with yellow orange pruina (UV –, POL +, soluble in K), more prominent in younger apothecia; exciple dispersa - type (Bungartz et al. 2007), 25–40 µm thick, inner excipular hyphae narrow, pale brown, outer excipular hyphae parallel, dark brown, without aeruginose pigments (K–, HNO 3 –); epihymenium brown, 8–10 μm thick, K–, HNO ₃–; hymenium hyaline, 40–70 µm high, not inspersed with oil droplets; paraphyses simple to moderately branched, apically swollen, with brown pigment cap (cf. elachista brown), aeruginose pigment absent; hypothecium dark brown, 100–120 μm high. Asci clavate, Bacidia- type, up to 8-spored. Ascospores 1-septate, brown at maturity, oblong to ellipsoid, usually not constricted at septum, not curved, Buelliatype, proper septum and spore wall thin, not thickening during spore ontogeny, ornamentation absent, (8.5–)9.3–10.9(– 11.7) × (5.2–)5.6–6.3(–6.8) µm, l/w= (1.5–)1.6–1.8(–2.0) µm (n = 30). Pycnidia not observed. Chemistry: Spot tests: K+ yellow soon turning red (forming crystals), P+ orange, C−. Thallus UV + pale white. TLC: norstictic acid (major), connorstictic (minor) and a unknown substances at approx. Rf value 70 (minor, paleyellow spot, less visible in natural light, LW UV: pale yellow green). Etymology: The species epithet “ austroindica ” refers to the southern part of India, the type locality of the new species. Distribution: The new species is known only from the type locality in Deccan region of India. It was growing on siliceous rock in a semi-shaded environment in a hilly forest area at an elevation of about 1,600 m. Notes: Buellia austroindica can be recognized by its brownish yellow, rimose areolate thallus, amyloid medulla, orange pruinose apothecial disc and the presence of norstictic acid. The pigment in Buellia austroindica is pale white under UV light and spot on TLC plate is not clearly visible under natural light in TLC. However, a closer observation under long-wave (366 nm) ultraviolet light, a pale yellow-green spot at approx. Rf value 70 is detected. The pruina appeared POL+ and intermixed with the epihymenium, dissolving in KOH. Morphologically, Buellia halonia (Ach. 1803:47) Tuck (1866:26) shares similarities with B. austroindica in having a pale yellow to brownish thallus, however, B. halonia has a distinctly areolate thallus, apothecia in close groups, discs lacking pruina, it produces xanthones as major substances, and occasionally has bright red pigment (eumitrin) in its medulla, its exciple is much better developed and belongs to the leptocline- type containing an aeruginose HNO 3 +violet pigment, additionally, it has larger ascospores of size 12–19 × 6–9 µm (Grube et al. 2004, Bungartz et al. 2007 & Elix 2016). Buellia argillicola B. de Lesd. (1929:243) is another species containing norstictic, connorstictic acid and weak traces of xanthones. However, it differs from B. austroindica by the presence of calcium oxalate, adnate apothecia, much larger ascospores (15–18.5 × 6.5–8.1 µm), stictic, hypostictic acid and it grows on limestone (Bungartz 2004). An Indian species Buellia pinicola S.R. Singh & D.D. Awasthi (1981:181) has orange pruina on apothecial discs but differs from B. austroindica in lacking secondary metabolites, having a greenish grey thallus and a corticolous habitat (Singh & Awasthi 1981).