Xanthoria polycarpa
≡Lobaria polycarpa Hoffm., Dtschl. Fl.: 136 (1796).
Description : Thallus (2–)5–10(–20) mm diam., forming small, rounded to elongated hummocks or cushions. Lobes 0.05–0.2 mm wide at margins and there crenulate-lobulate to delicately coralloid, widening to 1–2 mm centrally, 1–3 mm long and tapering from centre to margins, ±discrete to densely imbricate at margins, obscured by apothecia centrally. Upper surface ±convex, minutely lumpy-papillate (×10 lens), pale grey-green (in shade) to mustard-yellow to orange (in high light), without isidia or soredia. Lower surface white, pale-greenish at margins, corticate, ridged-striate, matt, with scattered, short white attaching hapters. orange. Apothecia ±crowded centrally, rounded to contorted through mutual pressure, 0.05–1.5(–3) mm diam., shortly pedicellate, pedicel broad, as wide as or slightly less than disc, margins persistent, broad and obscuring disc at first, narrowing with age, entire, minutely roughened-crenulate, concolorous with thallus; disc concave at first becoming plane to undulate with age, greenish yellow to mustard-yellow to orange, matt. Ascospores 11–15 × 6– 8 μm. Pycnidia scattered, minute, papillate,
Chemistry : Parietin (major), teloschistin, fallacinal, parietinic acid and emodin (minor) (Søchting 1997).
N: Taranaki (New Plymouth). S: Canterbury (Christchurch, Lincoln), Otago (Teviot, Mt Benger, Dunedin, Brighton), Southland (Te Anau, Lumsden, Riversdale, Gore, Invercargill). On twigs and/or trunks of mainly introduced trees being most commonly found in parks, gardens, roadside plantings and hedges, and very rarely in modified tussock grasslands grazed by sheep and cattle. Also on painted wooden surfaces such as exposed rafters and pergolas. In a garden setting, it will colonise young trees of Betula pendula, within 4–5 years of planting, and is an early coloniser of bark wounds from pruned branches. In urban habitats it appears to be able to withstand moderate to high levels of atmospheric pollution. It occurs on the following phorophytes: Acer pseudoplatanus, Berberis glaucocarpa, Betula pendula, Crataegus monogyna, Fraxinus excelsior, Gingko biloba, Larix europaea, Prunus × domestica, Prunus serrulata, Quercus robur, Rosa rubiginosa and Sophora microphylla, with all but S. microphylla being introduced trees. Specimens are always small (and are often overlooked) and tend to develop on rather young, smooth surfaces, being lost as the bark ages and furrows. This probably explains why it has been so infrequently collected to date. X. polycarpa associates with the following lichens: Amandinea punctata, Caloplaca inclinans, Candelariella reflexa, Hyperphyscia adglutinata, Lecanora carpinea, Parmelina labrosa, Physcia adscendens, P. poncinsii, Ramalina celastri, R. glaucescens, Rinodina exigua, Teloschistes chrysophthalmus, T. velifer, Xanthoria parietina (Galloway 1998a). It appears likely that it is an introduced species in New Zealand (Galloway 1998a). It is a widespread circumboreal-montane lichen of bark known also from the British Isles, Europe, Scandinavia, Morocco, the Ukraine, and North America (Purvis et al. 1992; Nimis 1993; Santesson 1993; Goward et al. 1994b; Esslinger & Egan 1995; Egea 1996; Kondratyuk et al. 1996a; Brodo et al. 2001; Lindblom 2004b), but not recorded from Australia (McCarthy 1999, 2003c).
Bipolar
Illustrations : Moberg & Holmåsen (1982: 190); Wirth (1987: 506; 1995b: 977); Kärnefelt (1989: 194, fig. 123); Dobson 1992: 363 & pl. 16; 2000: 413; 2005: 464); Goward et al. (1994b: 139, fig. 2A); Lindblom (1997: 119, fig. 14C); McCune & Geiser (1997: 322); St. Clair (1999: 223); Brodo et al. (2001: 747, pl. 921); Honegger et al. (2004a: 481, fig. 1F); Sérusiaux et al. (2004: 180).
Xanthoria polycarpa is characterised by: the corticolous/lignicolous habit; small, rounded to elongated, cushion-like thalli of congested-imbricate, ±tapering, subterete lobes, often almost coralloid at the margins, which are often hidden by the crowded apothecia discs, which are large and expanded centrally and small and poorly developed at margins. It is not easily confused with any other species of Xanthoria in New Zealand but is similar in some respects to the northern Teloschistes xanthorioides, which has a hummocky thallus and well-developed central apothecia obscuring the thallus. However, T. xanthorioides has well-developed white rhizines on the lower surface of the thallus, and larger fruits, which are distinctly pedicellate. Xanthoria polycarpa is a very uniform species throughout its range in New Zealand, differing mainly in the colour of the thallus depending on the light regime (and the corresponding development of parietin in the upper surface) of the substratum. Collections from shaded and/or polluted inner-city sites are generally greenish-yellow to green-grey or grey, while collections from high-light environments are conspicuously orange.
