Xanthoparmelia exillima
≡Parmelia exillima Elix, Austral. J. Bot. 29: 357 (1981).
Description : Thallus subcrustose, tightly appressed to rock substratum, yellow-green, darkening with age, subirregularly lobate or commonly becoming almost crustose centrally, 2–4(–7) cm diam. Lobes subirregular to sublinear-elongate, congested, 0.2–0.5 mm wide, plane or convex. Upper surface opaque, emaculate, isidiate. Isidia cylindrical, simple or commonly branched, often dark or blackened at apices, to 0.3 mm tall. Medulla white. Lower surface plane, yellow-brown to dark-brown, sparsely rhizinate. Rhizines sparse, concolorous with lower surface. Apothecia rare, adnate, 1–2 mm diam., disc brown to dark-brown, concave at first then ±plane; thalline exciple entire to crenate, exciple smooth. Ascospores 7–9 × 4–5.5 μm.
Chemistry : Thallus K−; medulla K−, C−, KC+ rose-pink, Pd−; containing usnic acid, norlobaridone, ±loxodin, ±atranorin and ± an unidentified compound.
S: Otago (Central Otago). On schist rocks. Also in Australia (Elix et al. 1986b: 245; Elix 1994s: 240; McCarthy 2003c, 2006).
Australasian
Illustrations : Elix (1981b: 356, fig. 6 – as Parmelia exillima); Hale (1990: 114, fig. 40B); Elix 1994s: 244, fig. 97B).
Xanthoparmelia exillima is characterised by: the saxicolous habit; cylindrical isidia; a pale lower surface; and norlobaridone in the medulla. It is similar to X. amplexula, but X. amplexula has adnate to loosely adnate, foliose thalli with much broader (1–3 mm), elongated lobes, while X. exillima is subcrustose in part with very narrow (0.2–0.5 mm), highly congested lobes. In addition, X. exillima rarely produces loxodin, which always accompanies usnic acid and norlobaridone in X. amplexula.
