Buellia pruinocalcarea Aptroot, M.F. Souza & Spielmann, sp. nov.
Index Fungorum number: IF 900068; MycoBank number: MB 900068; Facesoffungi number: FOF 13389; Fig. 1
Saxicolous Buellia on limestone with thallus thick, white, apothecia flush with the thallus, densely white pruinose, and ascospores 12–14×6–7 µm.
Holotype – Aptroot 77815.
Etymology – Named after the white pruina and the calcareous habitat. Sexual morph: Thallus crustose, covering areas up to 20 cm diam., marginal 3 mm continuous, remaining parts rather regularly cracked with areoles flat, c. 0.5 mm diam., not corticate, dull, almost pure white, very regularly c. 0.3 mm thick, not surrounded by a prothallus, but margin thinner though at least 0.1 mm thick. Isidia and soredia absent. Ascomata numerous, singly or aggregated, partly in concentrical zones (especially the outer rim of apothecia at 3 mm from the margin), immersed, flush with the thallus, rather uniformly 0.3–0.5 mm diam., sparse, solitary, disc flat, grey, margin barely raised, c. 0.05 mm thick, white, both disc and margin densely white pruinose. Excipulum uniformly dark brown in section. Epihymenium a layer of c. 15 µm high of brown paraphysal tips overlain with an c. 25 µm high epipsamma composed of many grey crystals that do not dissolve in K (calcium oxalate). Hymenium 70–90 µm high, hyaline, not inspersed, amyloid, paraphyses 1–1.5 µm wide, with dark brown upper. Hypothecium dark brown, in the central part up to 75 µm high, towards the margin tapering to c. 25 µm high. Ascospores 8/ascus, brown, 1-septate, ellipsoid, 12–14×6–7 µm. Asexual morph: not observed.
Chemistry – Thallus and apothecia UV +patchily salmonorange, especially in the submarginal zone, C–, P–, K–. TLC: nil.
Ecology and distribution – On exposed limestone in Atlantic rain forest biome; only known from Brazil.
Material examined – Brazil, Mato Grosso do Sul: Serra da Bodoquena, Bodoquena, Dente de Cão, summit, alt. 450 m, 20° 47ʹ 05″ S, 56° 45ʹ 03″ W, on exposed limestone in Atlantic rain forest biome, 7 November 2018, Aptroot 77815 (holotype, CGMC).
GenBank number – MW322683 (ITS).
Notes – This species is not keyed out in Malme (1912). It shows similarities with species of the Buellia subalbula (Nyl.) Müll. Arg. aggregate (Bungartz et al. 2011) and seems most similar to Buellia amabilis de Lesd. (see Bungartz and Nash 2004), which differs by the ornamented ascospores and the apothecia that become more convex, and the absence of UV luminescence. Phylogenetically, it clusters deep inside Buellia De Not. in the current sense (Fig. 1). Sequences of other species of the B. subalbula aggregate are not available. As part of a continuous effort to explore lichenologically relatively unidentified regions in Brazil, we investigated the microlichens on an isolated limestone outcrop in a tropical south-western inland region, viz. the Dente de Cão in the Parque Nacional da Serra da Bodoquena in the state of Mato Grosso do Sul, close to the borders with Paraguay and Bolivia. This range of hills is the only larger forested area still in existence in this state. Many microlichens were recently reported from the area (Aptroot and Spielmann 2020). This area is close to the venue of IAL9, the nearby town of Bonito.
Figure 1 – Buellia pruinocalcarea (Aptroot 77815 holotype) a. habitat. b. Upper and lower left in daylight. c. lower right in 365 nm UV light. Scale bars: a-c=20 mm