Xanthoria elegans
≡Lichen elegans Link, Annln Naturg. Göttingen 1: 37 (1791).
≡Rusavskia elegans (Link) S.Kondratyuk & Kärnefelt, Ukrayins'kyi Botanichnyi Zhurnal 60 (4): 434 (2003).
Description : Flora (1985: 618).
Chemistry : Parietin (major) with minor amounts of emodin, teloschistin, fallacinal, fallacinol, xanthorin parietinic acid, erythroglaucin, confluentic acid, notatoxanthin, lutein, cryptoxanthin, and β-carotene (Culberson et al. 1977; Fahselt & Krol 1989; Arnold & Poelt 1995; Søchting 1997).
S: Marlborough (Waihopai Valley), Canterbury (Craigieburn Ra., Godley Valley, Ben Ohau Ra.), Otago (St Bathans Ra., Dunstan Mts, Old Man Ra., The Remarkables, Mt Benger, Umbrella Mts, Poolburn Reservoir, Rough Ridge, Rock & Pillar Ra., Teviot Valley, Millers Flat). Characteristically growing on steep to vertical rock walls and bluffs in nivation cirques, and on dry, upward-facing ledges and underhangs of schist tors which are a prominent feature of the flat-topped mountains of Central Otago. It also colonises concrete fenceposts, concrete telephone poles and sunny exposed surfaces of concrete retaining walls of some Central Otago irrigation dams (e.g. Falls Dam, Poolburn Reservoir). The species grows in both sunny and shaded sites, being largely snow-covered in winter months. It has an altitudinal range of 700–2000 m. It is still very much undercollected in New Zealand and its ecological requirements imperfectly known. It associates with other bipolar alpine lichens such as Lecanora cavicola and L. swartzii in sheltered crevices and overhangs in high-alpine sites on the Central Otago mountain summits, a habitat also supporting small populations of Ramalina fimbriata.
Xanthoria elegans is a widespread, bipolar lichen with a wide ecological tolerance and a high degree of morphological variation (Hasselrot 1953; Fahselt & Krol 1989; Nimis 1993). Almborn (1987: 409) remarks of it: "In arctic-alpine regions of the Northern Hemisphere it is a widespread lichen at all levels. In South America it is known from the Andes (3500 – 4000 m), from Patagonia and Tierra del Fuego." Published records include Italy (Nimis 1993), Spain (Egea & Llimona 1981), Great Britain (Purvis et al. 1992), Scandinavia (Santesson et al. 2004; Elvebakk & Bjerke 2006), United States and Canada (Fink 1935; Hale & Cole 1988; Esslinger & Egan 1995; Lindblom 2004b), South Africa (Almborn 1987), East Africa (Swinscow & Krog 1988), and Morocco (Egea & Rowe 1987). In northern Chile on the alteplano close to the Bolivian border it occurs on rock outcrops at 4500 m (Galloway & Quilhot unpublished observations). In the South Pacific it is absent from both Australia and Tasmania (Kantvilas 1994b; Filson 1996; McCarthy 2003c, 2006), but is known from Macquarie I. (Kantvilas & Seppelt 1992; Filson 1996; McCarthy 2003c, 2006) and Marion I (Øvstedal & Gremmen 2001). It occurs widely in Antarctica (Dodge & Baker 1938; Dodge 1948, 1973; Murray 1963b; Filson 1966, 1974b; Lindsay 1971b, 1972; Redón 1985; Castello & Nimis 1995; Seppelt et al. 1995; Øvstedal & Lewis Smith 2001). The cortical pigment parietin is an effective UV-B screening compound in this lichen (Nybakken et al. 2004).
Bipolar
Illustrations : Filson (1966: 93, pl. 13 – as Caloplaca elegans var. pulvinata); Jahns (1980: 241, pl. 605); Moberg & Holmåsen (1982: 192); Thomson (1984: 484); Redón (1985: figs 33, 91); Wirth (1987: 503; 1995b: 975); Kärnefelt (1989: 169, fig. 42; 195, fig. 127); Goward et al. (1994b: 139, fig. 2A); Hansen (1995: 72); Johnson et al. (1995: 338); McCune & Geiser (1997: 319); St. Clair (1999: 221); Purvis (2000: 68); Dobson (2000: 412; 2005: 463); Brodo et al. (2001: 744, pl. 916); Øvstedal & Lewis Smith (2001: pl. 63, pl. 103); Kondratyuk (2004d: 278, fig. 111 – as Rusavskia elegans); Sérusiaux et al. (2004: 181); Pope (2005: 29).
Xanthoria elegans is characterised by: the saxicolous habit; rosette-forming thalli 3–6 cm diam., composed of radiating, narrow, convex lobes, 0.5–1 mm wide and 3–8(–10) mm long, not tapering from centre to apices, discrete or contiguous at margins and often to centre or ±imbricate centrally. Upper surface orange-red, smooth, wrinkled or ±nodular, minutely faveolate or pitted, without maculae. Apothecia central, disc orange-red, margins persistent, thin, concolorous with thallus, without rhizines below. Xanthoria elegans is a rather constant species in New Zealand, varying only in thallus colour, depending on the light regime of the substratum, and in the degree of apothecial development. A recent molecular study (Murtagh et al. 2002) demonstrates a high degree of genetic diversity within this widespread species and raises the possibility of cryptic speciation in diverse populations.
