Xanthoria incavata
≡Physcia incavata Stirt., Trans. N. Z. Inst. 32: 82 (1900).
≡Xanthoria parietina var. incavata (Stirt.) Js.Murray, Trans. Roy. Soc. N. Z. 88: 202 (1960).
≡Oxneria incavata (Stirt.) S.Kondratyuk & Kärnefelt, Ukrayins'kyi Botanichnyi Zhurnal 60 (4): 431 (2003).
Lectotype: New Zealand. South I., Canterbury, Selwyn Gorge, on "ribbon wood" trees, v.1894, T.W.N. Beckett No. 35 – BM [fide Kondratyuk & Galloway 1996: 191]. Epitype: New Zealand. South I. Marlborough, tributary of upper Awatere River, Molesworth, Flapper's Gully, Molesworth Station, on Hoheria lyallii, 16.iii.1947, H.H. Allan – CHR 378018!, duplicate in OTA [fide Kondratyuk & Galloway 1996: 191].
Description : Thallus rounded, in neat rosettes 2–7 cm diam., closely attached centrally and at margins, corticolous. Lobes 8–20(–35) mm long and 3–5 mm wide, moderately thick, occasionally discrete from margins to centre, generally ±imbricate, margins rounded, entire, conspicuously thickened below. Upper surface plane to undulate, shallowly ridged or pitted, matt, coriaceous, pale yellow-white or yellow at margins, darkening centrally. Lower surface white, smooth, with 1–2 rows of short (0.1 mm tall), tufted discontinuous groups of white rhizines along lower side of margins, elsewhere with scattered white anchoring rhizines 0.5–1 mm long. Apothecia sessile to subpedicellate, clustered centrally, rounded to irregular through mutual pressure, (0.5–)1–2(–3) mm diam., disc matt, orange, plane to subconvex or shallowly undulate; thalline exciple concolorous with thallus, thick, persistent, entire, occasionally with short, tufted, whitish rhizines below; proper exciple pseudoproso-plectenchymatous. Asci 57–65 × 16–18 μm. Ascospores 14–5–19 × 7.2–10 μm. Pycnidia scattered or in small groups, submarginal and laminal, slightly raised, orange, with a darker apical pore.
Chemistry : K+ purple; containing parietin.
S: Marlborough (Molesworth), Canterbury (Ashley Gorge, Selwyn Gorge). Xanthoria incavata is a corticolous species in the Xanthoria parietina -group, so far known only from bark of Acer pseudoplatanus, Hoheria and Populus nigra where it associates with Haematomma babingtonii, Hyperphyscia adglutinata, H. plinthiza, Phaeophyscia hispidula, P. orbicularis, Physcia adscendens, P. jackii, Punctelia subrudecta and Teloschistes velifer. It is still extremely poorly collected and understood in New Zealand and its ecological requirements are not fully understood (Kondratyuk & Galloway 1996).
Endemic
Illustration : Kondratyuk & Galloway (1996: 190, fig. 1).
Xanthoria incavata is characterised by: the corticolous habit; neat, rosette-forming thalli 2–7 cm diam., with entire, rounded margins conspicuously thickened and inrolled below and there furnished with 1–2 discontinuous rows of short, whitish rhizines, with larger more scattered whitish rhizines elsewhere on the lower surface. The upper surface is pale-yellowish to yellow-orange, matt and coriaceous. Apothecia are ±central, rounded, subpedicellate with occasional whitish rhizines developing on the thalline exciple below the disc. The proper exciple is prosoplectenchymatous, a type found also in Xanthomendoza (q.v.) and in the recently described Xanthoria bonae-spei (Kodratyuk et al. 2004a: 354–355). Xanthoria incavata from the few specimens examined is a rather constant species similar to X. parietina, but differing from it in the mode of attachment to the substratum (rhizines at lobe margins and scattered elsewhere on the lower surface, rather than scattered hapters as in X. parietina); the thickening and inrolling of the lower surface of the lobe margins; the generally smaller apothecia with occasional excipular rhizines, and the thicker, more coriaceous lobes. Additional collections are necessary to establish unequivocally the limits of variation in this species. It is possible that X. incavata might be better accommodated in Xanthomendoza (q.v.) though a definite opinion on its true status has not yet been settled (Søchting et al. 2002; see aslo Kondratyuk et al. 2004a: 354–355), and recently Kondratyuk & Kärnefelt (2003) transferred it to the new genus Oxneria, though this is still somewhat in doubt.
