Acarospora fuscata
≡Lecanora fuscata Nyl., Not. Sällsk. Faun. Fl. fenn. Förh. 8: 138 (1866) ["1882"].
Description : Thallus of contiguous to scattered areolae; areolae very variable, 0.5–3 mm diam., round to angular, flat to sublobulate, pale to dark reddish brown, or yellow-brown; margins and lower surface black. Apothecia numerous, 1–5 per areola, 0.2–1 mm diam., immersed, punctiform to concave, disc dark red-brown to black, epruinose. Epithecium yellow-brown, 10–15 μm thick. Hymenium 80–120 μm tall. Ascospores narrowly ellipsoidal to cylindrical, 4–6 × 1–1.5 μm.
Chemistry : K−, KC+ red, C+ red, Pd−; containing gyrophoric acid.
S: Otago (Teviot Valley, Dunedin). On concrete bridge piers, capping stones of University Bridge. Widespread in the Northern Hemisphere where it occurs on sunny, nutrient-enriched siliceous rocks, and is common in cities and on monuments in rather polluted areas (Magnusson 1936; James 1973; James et al. 1977; Purvis et al. 1992; Nimis 1993; Santesson 1993; Esslinger & Egan 1995; Elvebakk & Hertel 1997; Llimona & Hladun 2001; Nimis & Martellos 2003; Temina et al. 2005), and known also from Australia (McCarthy 2003c).
Cosmopolitan
Illustrations : Galløe (1936: p. 47, pls 44–46); Ozenda & Clauzade (1970: 506, fig. 420); Brodo (1981: 16, fig. 1); Moberg & Holmåsen (1982: 164); Wirth (1987: 38; 1995b: 105); Foucard (1990: pl. 5); Dobson (1992: 8; 2000: 45 ; 2005 : 51); Brodo et al. (2001: 146, pl. 92); Pope (2005: 58); Temina et al. (2005: 438, pl. 1D).
Acarospora fuscata is characterised by: the saxicolous habit (basicolous substrata); the yellow-brown to dark reddish brown areolate thallus, the areolae raised at the edges somewhat like dried mud; the sunken, dark red-brown apothecia; and the C+ red reaction (gyrophoric acid).
