Diplotomma alboatrum
≡Lichen alboater Hoffm., Enum. lich. eur.: 30 (1784).
≡Buellia alboatra (Hoffm.) Th.Fr., Gen. heterolich. Eur. recog.: 91 (1861).
Description : Flora (1985: 162).
Chemistry : Thallus K−, Pd−, sometimes K+ yellow→red, Pd+ orange, then containing norstictic acid.
N: Sine loco (Colenso, BM), Wellington (Wairarapa, Scorching Bay). S: Canterbury (Weka Pass, Castle Hill, Flock Hill), Otago (Duntroon, Taieri Mouth), Southland (Castle Rock near Dipton, Clifden). Most commonly on weathered limestone rocks, but known also from coastal schist (Taieri Mouth). Elsewhere in its range it colonises a variety of substrata including: rough bark of deciduous trees, siliceous seashore rocks, calciferous substrata (e.g. limestone), rarely on lignum and it is also (when young) parasitic on other lichens, e.g. Caloplaca and Xanthoria (Nordin 1996, 2000). Known also from Great Britain, Europe, Scandinavia, Iceland, Greenland, the high-Arctic, North Africa, East Africa, South Africa, North and Central America, Juan Fernandez, the Falkland Is and Australia (Nordin 2000 [distribution mapped p. 53, fig. 18], Coppins 2002b, Foucard et al. 2002; McCarthy 2003c, 2006; Nimis & Martellos 2003; Santesson et al. 2004).
Cosmopolitan
Illustrations : Moberg & Holmåsen (1982: 194 – as Buellia alboatra); Wirth (1987: 80; 1995: 194 – as Buellia alboatra); Nordin (1996: 338, fig. 7A–C – as Buellia alboatra); Boqueras (2000: 123, fig. 15 – as Buellia alboatra); Dobson (2000: 153; 2005: 168); Nordic Lichen Flora2 (2002: 90 – as Buellia alboatra).
Diplotomma alboatrum is characterised by: the subsquamulose, rather lumpy or warty, whitish or greyish thallus; abundantly developed, small, immersed to subsessile apothecia, with plane to convex black discs usually thickly grey-white-pruinose; brownish, 3-septate to submuriform ascospores with obtuse apices, 15–18.5 × 6–8 (–8.5) μm . Variation in this species is discussed by Nordin (1996: 339–341; 2000: 51–58).
