Flora of New Zealand Series

=RUSAVSKIA S.Kondratyuk & Kärnefelt, 2003

Type : Parmelia parietina (L.) Ach. [(=Lichen parietinus L.) =Xanthoria parietina (L.) Th.Fr.]

Type : Rusavskia elegans (Link) S.Kondratyuk & Kärnefelt [Xanthoria elegans (Link.) Th.Fr. (=Lichen elegans Link)]

Description : Thallus foliose to subfruticose, forming separate rosettes or coalescing into swards ±covering the substratum. Lobes dorsiventral to subterete, ±horizontal to semi-erect to erect, smooth to wrinkled, mostly frequently branched. Upper surface in shades of orange to yellow, variable, occasionally greenish or grey, sometimes white-pruinose. Cortical layers paraplectenchymatous, of 3–5 layers of isodiametric to somewhat elongated cells, colourless apart from external anthraquinone crystals. Medulla of loosely arranged rather lax hyphae. Photobiont green, Trebouxia -like, unicellular, to 25 μm diam., in a ±continuous layer near the upper cortex, or in groups spread throughout medulla. Lower surface white to yellow, smooth to somewhat wrinkled. Attachment organs mostly present, submarginal to scattered, simple, white to yellow, developed as hapters (±short and attached with ±pronounced terminal extensions or "feet") or rhizines (short to long, free or attached, pointed to ±frayed). Soralia present or absent, laminal or marginal to submarginal, blastidious or soredious, concolorous with the upper surface or paler yellow to greenish yellow. Ascomata apothecia, present or absent, laminal, sessile to ±pedicellate, disc darker than thallus, occasionally with a white pruina. Thalline margin concolorous with thallus, sometimes with short hapters or short to long rhizines, smooth to sorediate, occasionally with lobules. Exciple cupular (see Jahns et al. 1995b), thin to thick, cells with thick walls and ±elongate lumina. Hypothecium colourless to pale-brown, irregular, cells thin-walled, sporadically with oil droplets. Hymenium colourless in lower part, and with anthraquinone crystals in a ±distinct layer in upper parts. Hamathecium of paraphyses, simple or branched, often with scattered anastomoses in lower parts, apices ±capitate, occasionally or frequently with oil droplets in uppermost cells. Asci Teloschistes -type, clavate, 8-spored. Ascospores polaribilocular, hyaline, ellipsoidal to cylindrical, 10–20 × 4–10 μm, septum narrow to wide, 1–10 μm. Conidiomata pycnidia, ±conspicuous, laminal, immersed to protruding, concolorous with thallus or darker (Xanthoria -type; see Vobis 1980). Conidia ellipsoidal or bacillar, 2–5 × 1–2 μm.

Chemistry : Thallus and apothecia K+ purple, C−, Pd; characterised by anthraquinones parietin (major) with lesser amounts of emodin, fallacinal, parietin, parietinic acid and teloschistin (Arnold & Poelt 1995; Søchting 1996, 1997).

Xanthoria, included in the family Teloschistaceae (Erikssson et al. 2004; Pennycook & Galloway 2004), is a genus of c. 30 species worldwide (Lindblom 2004b). The bright orange-yellow species of Xanthoria are conspicuous lichens in the New Zealand landscape, being readily recognised and frequently collected, especially from coastal rocks and from urban environments and habitats with some degree of nutrient enrichment such as farms, orchards, bird perches etc. It is now 40 years since James Murray (1923–1961) wrote his pioneering paper on the family Teloschistaceae in New Zealand (Murray 1960b). Murray followed the taxonomic treatments of Johannes Hillmann (1881–1943) who had seen a range of material from New Zealand sent to him in the 1930s by H.H. Allan, and from which he described a new species, Xanthoria novozelandica (Hillmann 1938). Zahlbruckner (1941) transferred Physcia incavata (Stirton 1900) to Xanthoria, which Murray (1960b) reduced to varietal status as Xanthoria parietinavarincavata (Stirt.) J.Murray. In common with many taxonomists of the time, Murray formally recognised many infraspecific taxa for what are now considered to be only environmentally induced modifications of widespread and/or opportunistic species. The Flora account (Galloway 1985a: 617–620) drew heavily on Murray's work, but since that time further collections and study of urban lichens in New Zealand and of lichens as indicators of environmental pollution in a number of industrial sites from Northland to Southland, have added considerably to our knowledge of Xanthoria in this country.

Recent systematic work on Xanthoria has considerably clarified taxonomic limits and relationships of species groups and of individual taxa (Castello 1995; Elix 1988; Fahselt & Krol 1989; Filson 1969, 1984a; Giralt et al. 1993a; Honegger 1978a, 1990, 1996; Honegger et al. 1996, 2004a, 2004b; Kärnefelt 1989, 1990a, 1991, 1998; Kärnefelt & Thell 1994; Kondratyuk & Galloway 1994, 1996; Kondratyuk & Kärnefelt 1996, 2000; Kondratyuk et al. 1996c, 2000, 2001, 2004a; Kondratyuk & Poelt 1997; Lindblom 1997, 2004b; Ott 1987; Poelt & Petuschnig 1992a, 1992b; Richardson 1967; Scherrer & Honegger 2003; Scutari et al. 2002b; Søchting et al. 2002; Steiner & Poelt 1982). The genera Josefpoeltia and Xanthomendoza were recently segregated from Xanthoria  s. lat., (Kondratyuk & Kärnefelt 1996, 1997). Xanthomendoza (q.v.) is characterised by long, oblong to bacillar conidia, a unique structure of the apothecia, upper and lower cortices, and by the presence of true rhizines on the lower surface, and 16 species of Xanthoria were recently transferred to it (Søchting et al. 2002), including the New Zealand endemic X. novozelandica. Two futher genera were recently segregated from Xanthoria, viz. Oxneria Kondratyuk & Kärnefelt, the Xanthoria ulophyllodes group, and Rusavskia Kondratyuk & Kärnefelt, the X. elegans group (Kondratyuk & Kärnefelt 2003; Kondratyuk 2004a, 2004b), but both of these segregate genera are not yet widely accepted. At present, six species of Xanthoria are recorded from New Zealand.