Flora of New Zealand Series

≡Porina xanthostoma Sommerf., Kongl. Vetensk.- Akad. Handl. 1823: 115 (1824).

≡Pertusaria xanthostoma (Sommerf.) Fr., Lichenogr. Europ. Reform.: 426 (1831).

Description : Thallus off-white, ashy-grey, white or creamish white, thin, continuous, to granular–papillate, surface smooth and dull, overgrowing dead tussock bases, mosses, detritus and soil. Apothecia verruciform, concolorous with thallus, flattened–hemispherical, constricted at base, sometimes concave above, (0.1–)0.5–1.0 mm diam.; ostioles inconspicuous, 1–4 per verruca, hyaline to pale-yellow, yellow-brown or pinkish. Hypothecium hyaline to brownish. Epithecium K−, pale to dark. Asci clavate, often deliquescing before ascospores mature, (140–)220(–320) × 30–85 μm. Ascospores 4 per ascus (rarely 6–8 per ascus), uniseriate or biseriate, ellipsoidal to cylindrical, but often deformed and found liberated from ascus, 65–85 × 35–40 μm, walls double, thin, 1–2 μm thick, the inner wall smooth.

Chemistry : Medulla UV+ ice-blue, K−, KC+ red, C− or + pink, Pd−; containing alectoronic acid (major), and ursolic acid (tr.).

N: South Auckland (Te Aroha). S: Nelson (Mt Aorere, St Arnaud Ra.), Marlborough (Mt Stokes), Canterbury (Sugarloaf Cass, Craigieburn Ra., Torlesse Ra., Godley Valley), Otago (Humboldt Mts, Old Man Ra., Poolburn Reservoir, Mt Pisgah, Rock & Pillar Ra., Deep Stream). St: (The Paps, Cooks Arm Port Pegasus) C: A distinctive muscicolous/terricolous species found in subalpine to high-alpine environments overgrowing dead tussock bases, mosses and both living (e.g. Pentachondra pumila) and decaying vegetation on exposed soils. First described from Norway, it is known also from Alaska, Greenland, Iceland, Scotland and W Russia (Dibben 1980; Archer 1991a; Santesson 1993; Coppins 2002b). In the Southern Hemisphere it is known from New Zealand, Tasmania and Macquarie I. (Archer 1991a; Filson 1996; McCarthy 2003c, 2006).

Bipolar

Exsiccati : Elix (1990: No. 214 – as Pertusaria xanthostoma).

Illustrations : Dibben (1980: 154, fig. 121); Schmitz et al. (1994: 159, fig. 4G); Malcolm & Galloway (1997: 102).

Ochrolechia xanthostoma is characterised by: the muscicolous/terricolous habit; a thin, smooth, marginally unzoned, continuous, to granular–papillate, ashy-grey, white to creamish white thallus; numerous, concolorous poriform verrucae with sunken ostioles surrounded by a pinkish or yellow-brown border; clavate asci (soon deliquescing) with usually 4 thin-walled, uniseriate or biseriate ascospores; and a KC+ red medullary reaction indicating the presence of alectoronic acid. The record of Pertusaria tyloplaca Nyl. from Campbell I. being referable to O. xanthostoma (Galloway 2000a) is in error, the former taxon being an independent entity, having a similar habitat preference, but distinguished by having 8 biseriate ascospores per ascus; and the presence of stictic acid.