Flora of New Zealand Series

Description : Thallus orbicular to irregular, very variable in size, 1–4(–8) cm diam., ±closely adnate to substratum. Lobes sometimes imbricate, sometimes distinctly separated, very variable in width, 0.5–2 mm wide, 2–5(–15) mm long, flat to convex. Upper surface white to dark-grey, sometimes with scattered white dots, with or without pruina; sorediate. Soralia mainly laminal, crateriform to almost capitate, usually orbicular, starting from cracks in upper cortex, or sometimes marginal developing into rounded patches at angles of lobes. Lower surface white to pale brown-grey, with white to dark-grey rhizines. Upper cortex paraplectenchymatous. Lower cortex intermediate between prosoplectenchymatous and paraplectenchymatous. Apothecia rare, sparse to numerous, sessile, constricted at base, round to irregular, 0.5–2(–3) mm diam., thalline exciple concolorous with thallus, persistent, entire to crenulate or delicately scalloped, sometimes sorediate in patches; disc concave at first, becoming plane to undulate or convoluted, matt, brown-black, with or without a fine, grey-white pruina. Epithecium pale chestnut-brown, 12.5–22 μm thick. Hymenium colourless, 60–75 μm tall. Ascospores grey-brown Pachysporaria -type, (17–)20–22.5 × 7.5–11 μm.

Chemistry : Cortex and medulla K+ yellow; containing atranorin and zeorin.

N: Northland (Radar Bush) to Wellington. S: Nelson (Boulder Bank) to Southland (Tiwai Point). St: (Oban, Moturau Moana). Ch: (S of Waitangi). On coastal rocks and lowland coastal scrub and forest trees and shrubs. Common on trunks of introduced trees in parks, gardens and on street plantings where it appears to be tolerant of moderate levels of pollution. Possibly an introduced species in New Zealand. Known also from East and South Africa (Moberg 1986b, 2004b; Swinscow & Krog 1988); South America (Moberg 1990; Scutari 1995b; Marcano et al. 1996; Galloway & Quilhot 1999; Calvelo & Liberatore 2001), Florida and the Sonoran Desert in Baja California and Mexico (Harris 1995; Moberg 1997, 2002b) and Australia (Moberg 2001; McCarthy 2003c, 2006).

Palaeotropical

Illustrations : Moberg (1986b: 849, fig. 8c, 860, fig. 20); Swinscow & Krog (1988: 230, fig. 113); McCarthy & Malcolm (2004: 56).

Physcia poncinsii is characterised by: the corticolous/saxicolous habit; convex lobes with truncate apices; distinctive crateriform soralia; and a white lower surface. In earlier accounts of New Zealand lichens, this species was recorded as P. integrata var. sorediosa, P. stellaris var. radiata and P. stellaris var. rosulata (Zahlbruckner 1941: 378), and as P. tribacoides (Galloway 1985a: 384–395; 1992: 28; Malcolm & Galloway 1997: 33). It is a widespread and rather variable species, corticolous specimens having thinner and flatter lobes than saxicolous specimens, which generally have thick, convex, maculate lobes.