Flora of New Zealand Series

≡Lecidea parasema var. disciformis Fr., Nova Schedae Crit. Fasc. 8: 9 (1826).

≡Hafellia disciformis (Fr.) Marbach & H.Mayrhofer in B. Marbach, Biblthca Lichenol. 74: 264 (2000).

Description : Thallus thin, areolate, white to grey, irregular. Medulla ±amyloid. Apothecia sessile, to 1.5 mm diam., disc black, epruinose, margins usually persistent. Hymenium with oil droplets; epithecium olive-brown to brown. Hypothecium dark-brown. Ascospores Callispora -type, 1-septate, rarely 3-septate, apices somewhat pointed, 14–30 × 6–13 μm. Pycnidia common, conidia subcylindrical, 4–5 × 1 μm.

Chemistry : Thallus K+ yellow; containing atranorin.

S: Canterbury (Arthur's Pass, Hanmer, Lake Lyndon), Southland (S Mavora Lake). On bark of native and introduced trees, Alnus glutinosa, Dracophyllum acerosum, Nothofagus solandri var. cliffortioides. Often associating on mountain beech bark with the lichens Haematomma alpinum, Miltidea ceroplasta, Ochrolechia etc. Known also from Great Britain, Europe, Scandinavia, Canary Is, Socotra, North America and Australia (Purvis et al. 1992; Nimis 1993; Santesson 1993; Esslinger & Egan 1995; Scholz 2000; Marbach 2000; Coppins 2002b; McCarthy 2003c, 2006; Santesson et al. 2004; Mies & Schultz 2004).

Cosmopolitan

Illustrations : Moberg & Holmåsen (1982: 195); Dobson (1992: 70; 2000: 81 ; 2005 : 88).; Brodo et al. (2001: 187, pl. 146); Nordic Lichen Flora Vol. 2 (2002: 91).

Buellia disciformis is characterised by: the corticolous habit; the thin, grey-white thallus; sessile, black apothecia; and ascospores with slight apical thickenings (Callispora -type), 14–30 × 6–13 μm. Taxa with Callispora -type spore thickenings are referred by several authors to the genus Hafellia (Kalb 1986; Sheard 1992; Nimis 1993; Pusswald et al. 1994; Marbach 2000; McCarthy 2003c, 2006; Etayo & Marbach 2003), but if the typification of Buellia based on B. disciformis is upheld, Hafellia becomes a synonym of Buellia, a position adopted by many authors (e.g. Foucard et al. 2002; Coppins 2002b; Santesson et al. 2004), and accepted here.