Flora of New Zealand Series

≡Lichen parietinus L. Sp. Pl. : 1143 (1753). 

Descriptions : Flora (1985: 620).

Chemistry : Parietin (major), emodin, teloschistin, fallacinal and parietinic acid (minor) (Elix 1988; Søchting 1997).

N: Three Kings Is to Wellington. S: Nelson to Southland. St: Ch: Growing on a wide variety of substrata in high-light environments in predominantly coastal and/or lowland areas of New Zealand. A common epiphyte of both introduced and native trees and shrubs. Also on rocks (maritime and inland, both acidic and basic), wooden gates, railings and fences, glass, concrete, plastic nursery shading, bone, painted wood, gravestones and abandoned vehicles. It commonly occurs spreading over gravel chippings and bitumen on roadsides in country areas, where its distribution may be encouraged by ammoniacal enrichment from sheep urine derived from frequent passage of sheep trucks or other farm vehicles. In this habitat it is commonly associated with Physcia adscendens and P. caesia.

It is not found in beech (Nothofagus) or podocarp forests either E or W of the Main Divide, nor is it a component of alpine scrub vegetation above treeline, and is generally more common on introduced trees and shrubs and hedges in urban and rural environments than it is on native vegetation in unmodified environments. For this reason James Murray (1960b: 199) considered it may have been introduced. Recent molecular work on a wide range of freshly collected specimens worldwide (Scherrer & Honegger 2003: 387) supports this notion, with Australasian, North American and European material all being closely similar, with high sequence identity (up to 100%). It is however a component of the northern coastal flora where it is often present as an epiphyte of both scrub and forest vegetation (Hayward & Hayward 1973b, 1974a, 1979, 1980, 1983, 1984, 1986; Hayward et al. 1975, 1981, 1986, 1997; Hayward & Wright 1977; Wright et al. 1980; Galloway & Hayward 1987; Hayward & Hollis 1993). It is common and widespread in all main landmasses except Antarctica and the high-Arctic (Lindblom 2004b).

Cosmopolitan

Exsiccati : Vězda (1983b: No. 1897).

Illustrations : Filson (1969: 115, pl. 15); Jahns (1980: 241, pl. 602); Moberg & Holmåsen (1982: 191); Phillips (1987: 172); Wirth (1987: 504; 1995b: 977); Kärnefelt (1989: 194, fig. 119); Rikkinen (1995: 239, fig. 42); McCune & Geiser (1997: 321); Baron (1999: 10. pl. 4); Dobson (2000: 413; 2005: 463); Purvis (2000: 9, 20, 27); Brodo et al. (2001: 86, pl. 75; 747, pl. 920); Scherrer & Honegger (2003: 381, fig. 2A, B); Honegger et al. (2004a: 481, fig. 1A); Kondratyuk (2004d: 315, fig. 131); Sérusiaux et al. (2004: 180).

Xanthoria parietina is characterised by: the corticolous/lignicolous/saxicolous habit; flat, yellow, yellow-orange or greyish (in shade), dorsiventral, ±rosette-forming to irregularly spreading thalli that are corticate on both upper and lower surfaces. It has entire margins and is attached to the substratum by short hapters (Kondratyuk & Poelt 1997: 174–175). It is usually copiously fertile (especially centrally), and has parietin as the major medullary compound. It is distinguished from X. incavata by the thinner, broader, plane or subconvex lobes which are generally without adventitious marginal lobules, by the ±raised margins, and by the wrinkled-pitted or faveolate upper surface. X. filsonii (Elix 1988) differs in the narrower lobes which are conspicuously downturned at the margins and apices, and by having teloschistin as the dominant medullary compound. Further screening of New Zealand collections of X. parietina is required to see whether some populations are referable to X. filsonii or whether this taxon is just part of the chemical variation of X. parietina  s. lat.  Xanthoria parietina is a very variable species throughout its range in New Zealand, especially in terms of its thallus colour, which varies from grey to yellow-grey to shades of yellow and orange depending on the light conditions of the habitat, with shade forms being pale-grey, and high-light forms being bright-orange, with a whole range of colours in between these two extremes. Murray (1960b) recognised many of these colour variants as separate taxonomic entities, a view no longer current. In some habitats thalli develop rather narrow lobes (the exact relationship between these narrow-lobed forms and X. filsonii still needs clarification), and in strongly eutrophicated habitats thalli may develop small, hummocky, subimbricate lobes rather than the normal, broad, plane lobes.