Characterized by the saxicolous habit and apothecia lacking internal pigmentation.
Type: Falkland Islands, West Falkland, Port Howard, Mt Maria, Castle Rock, 51.621332°S, 59.591020°W, 370 m, shaded, S-facing crags (underhang), 26 January 2015, Fryday 10902 (MSC—holotype).
Description
Thallus effuse, white, thin <50 µm thick, with rock grains protruding through the surface, rimose to cracked-areolate; medulla I–. Photobiont trebouxioid; cells 9–15 µm diam.
Apothecia biatorine, white, pink to pale orange, 0.6–0.8–1.0 mm diam., disc flat becoming convex, white pruinose; margin prominent when young, 0.15 mm wide, persistent but barely raised in older apothecia, 0.05 mm wide. In section:proper exciple well developed, c. 120 µm wide, composed of narrow, 1.5 µm wide, richly branched and anastomosing hyphae, inspersed with granular crystals that form bands towards the outer surface and dissolve in K to give a bright yellow solution; cortex absent; extending in a narrow band under the hypothecium and forming a deep, conical ‘root’ 100–120 µm into the thallus. Hymenium 50–65 µm high, upper 10–20 µm with granular crystals that mostly dissolve in K; paraphyses thin, 1.5 µm wide, widening at the apex to 4 µm, sparingly branched and anastomosing. Hypothecium hyaline 35–50 µm high, composed of randomly orientated hyphae, well differentiated from the hymenium. AsciBiatora-type, cylindrical, 35–40 × 15 µm, becoming clavate and 20 µm wide; ascospores hyaline, 1-septate, (11–)12.33±0.89(–14) × (4.5–)4.96±0.45(–5.5) µm, l/b ratio (2.18–)2.50±0.23(–2.89), (n = 12).
Conidiomata not observed.
Chemistry. K+ yellow, C–, KC–, Pd+ orange-red; thallus too thin for TLC.
Etymology. Named for the white apothecia.
Distribution and Ecology. Known only from the Falkland Islands. Reported from siliceous rocks on both main islands, usually at relatively high altitudes (180–370 m). Associated species: Cliostomum longisporum Fryday, Lecanora spegazzinii Müll. Arg., Lepra macloviana (Müll. Arg.) I. Schmitt, B.G. Hodk. & Lumbsch, Ramboldia petraeoides, Rhizocarpon malvinae Fryday, R. geographicum (L.) DC. aggr.