Xanthopsoroma contextum
Family
Pannariaceae
Flora category
Lichen – Native
Endemic taxon
No
Endemic genus
No
Endemic family
No
Structural class
Lichens - Crustose
Current conservation status
2018 | Not Threatened | Qualifiers: SO
Brief description
Characterised by the corticolous habit, the squamulose thallus developing on a rather thin, black, scattered to somewhat eroded prothallus; thalline squamules 1–3 m diam., flattened, lobate-crenate, surface waxy, smooth, pressed together and separated by fine black lines like a jigsaw puzzle, rarely imbricate at margins, becoming minutely lobulate and subimbricate centrally, margins not “frosted”; rather rare, simple, globose to glomerulate cephalodia developed below squamules and projecting from margins of squamules; apothecia projecting above squamules, 1–2 mm diam., margins waxy, crenate-striate, the disc red-brown often darkening centrally, and rarely with a few scattered thalline lobules; and ellipsoidal ascospores, 18–24 × 12–17 μm.
Distribution
North Island: Wellington (Wellington) South Island: Nelson (Denniston Plateau), Westland (Ngatau Valley), Canterbury (Nina Valley, Arthur’s Pass, Cass), Otago (Forgotten River, Lake Wilkie Catlins), Southland (Stuart Mts, Caswell Sound). Stewart Island (Sylvan Cove Port Pegasus). Auckland Islands: (Carnley Harbour, Enderby Island).
Known also from Argentina and South East Australia.
Habitat
Throughout, mainly W of the Main Divide in South Island, in Fuscospora forest on bark and wood and among mosses on tree trunks and on twigs in damp, semi-shaded habitats.
Detailed description
Thallus squamulose, very closely attached, spreading, 4-6(-10) cm diam., prothallus only rarely present, black, thin, somewhat eroded, scattered. Squamules small, 1-3 mm diam., flattened, lobate-crenate, distinctly placodioid at margins, pressed together, separated by fine black cracks like a jigsaw puzzle, rarely imbricate at margins, becoming minutely lobulate and subimbricate centrally in a close mosaic, surface smooth, waxy, shining, margins not pubescent- frosted, dark green to pale green or whitish or yellowish-grey not darkening on storage. Cephalodia rare, simple, globose to ± glomerulate, not flattened- placodioid, pale brown-grey, surface smooth, not wrinkled or striate-cracked, developed below squamules, protruding from margins of squamules, to 0.8 mm diam. Apothecia sessile to subpedicellate, scattered to crowded, projecting above squamules, round to subirregular, to 2 mm diam., margins concolorous with thallus, waxy, crenate-striate, obscuring disc in young fruits, disc red- brown, matt, often darkening centrally, rarely with a single to a few thalline lobules centrally, plane or subconcave, not etched-contorted, fissured or pruinose. Ascospores ellipsoid to fusiform 18-24 × 12-17 µm.
Chemistry: TLC−, all reactions negative.
Similar taxa
This taxon is closely similar to Psoroma pholidotoides (q.v.) and may in fact prove to be conspecific with it. More work is needed on this and other taxa in the Pannaria implexa group.
Substrate
Corticolous
Attribution
Fact sheet prepared by Marley Ford (25 August 2021). Brief description, Distribution, Habitat, Features and Similar taxa sections copied from Galloway (1985; 2007).
References and further reading
Galloway D.J. 1985: Flora of New Zealand: Lichens. Wellington: PD Hasselberg, Government Printer. 662 pp.
Galloway D.J. 2007: Flora of New Zealand: Lichens, including lichen-forming and lichenicolous fungi. 2nd edition. Lincoln, Manaaki Whenua Press. 2261 pp.