Lecanora polytropa
Common name
granite-speck rim lichen
Family
Lecanoraceae
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 saxicolous/lignicolous habit; the clusters of yellow to tan apothecia with greenish yellow thalline margins, and the virtual absence of thallus.
Distribution
North Island: Gisborne (Mt Hikurangi). South Island: Nelson (Ruby Lake) to Southland (Invercargill). Stewart Island/Rakiura.
It is most common east of the Main Divide, especially on sunny, exposed schist surfaces, as well as in shaded overhangs in the Central Otago Mountains.
Known also from Great Britain, Europe, Scandinavia, the Arctic, Asia, North and South America, Australia, South Georgia, South Orkney Is, South Shetland Is, and the Antarctic Peninsula.
Habitat
On alpine to high-alpine rocks (schists and greywacke—to 3550 m on the exposed Middle Peak of Mt Haast), on flat, exposed rock surfaces, on pebbles in fellfield, and on vertical sides and roofs of overhangs and caves where it may become hummocky–pulvinate. It is quite common in urban environments on old painted surfaces of wooden railings, on stonework of bridges (e.g. the impressive stone bridge over the Leith at Woodhaugh Gardens in George Street, Dunedin, supports a vigorous growth of L. polytropa], on concrete coping and kerbing along fencelines where the surfaces are washed periodically by leached iron slats from metal railings and/ or fence-wires. On man-made substrata it commonly associates with Candelariella vitellina, Physcia adscendens, and P. caesia. It was recorded from a height of 7400 m in the Himalaya, the highest known elevation for lichens (Hertel 1977a, 1988a).
The presence of usnic acid as a photoprotective compound in this species allows it to survive comfortably in areas of high UV radiation (see Bjerke & Dahl 2002). It also commonly occurs on old weathered, rusted iron gates, railings (especially around headstones in graveyards), abandoned metal fluming, wheels, pipes and dredge buckets, on weathered lignum (including tops of tanalised posts in both rural and urban environments, where it often forms conspicuous, radiating, yellow-green patterns interspersed with bands of golden Candelariella), and old, abandoned farm and industrial machinery, and on flaking painted surfaces where the paint is rich in iron oxide.
Detailed description
Thallus pale grey-green to yellow-brown, ± warted-areolate, often reduced to scattered granules on a dark prothallus, or absent altogether. Apothecia clustered, round to irregular, pale yellow to pale yellow-brown, rarely darkening with age, 0.02-1.5 mm diam., concave and ± marginate at first, margins entire to ± crenulate, pale yellow (paler than disc), very thin, convex and immarginate at maturity. Ascospores ellipsoid, 9-14 × 5-6 µm.
Chemistry: Usnic and rangiformic acids and zeorin.
Similar taxa
The related species Lecanora stenotropa Nyl., said to be present in New Zealand (Lumbsch & Elix 2004: 50), is morphologically indistiguishable from L. polytropa, but has narrower ascospores (8–12 × 3–4 μm – those of L. polytropa are 9–15 × 4.5–7 μm), isorangiformic as main metabolite.
Substrate
Corticolous, saxicolous, man-made surfaces (metal, timber, concrete, wire)
In the Northern Hemisphere, Lecanora polytropa is commonly parasitised by several lichenicolous fungi including *Carbonea aggregantula (Müll.Arg.) Diederich & Triebel, *C. supersparsa (Nyl.) Hertel, *Cercidospora epipolytropa (Mudd) Arnold, and *Muellerella pygmaea var. athallina (Müll.Arg.) Triebel, all of which should be sought in New Zealand populations, which commonly show signs of parasitism by lichenicolous fungi.
Attribution
Fact sheet prepared by Melissa Hutchison (31 August 2021). Brief description, Distribution, Habitat, Features, Similar Taxa and Extra information sections copied from Galloway (1985, 2007).
References and further reading
Bjerke JW, Dahl T. 2002. Distribution patterns of usnic acid-producing lichens along local radiation gradients in West Greenland. Nova Hedwigia 75: 487-506. https://doi.org/10.1127/0029-5035/2002/0075-0487.
Galloway DJ. 1985. Flora of New Zealand Lichens. Government Printer, Wellington, NZ. 662 p.
Galloway DJ. 2007. Flora of New Zealand Lichens. Revised 2nd edition including lichen-forming and lichenicolous fungi. Manaaki Whenua Press, Lincoln, NZ. Two volumes: vol. 1 pp 1–1006; vol. 2 pp 1007–2261.
Hertel H. 1977. Gesteinsbewohnende Arten der Sammelgattung Lecidea (Lichenes) aus Zentral-, Ost-, und Südasien. Eine erste Übersicht. Ergebnisse des Forschungsunternehmens Nepal Himalaya Khumbu Himal 6 (3): 145–378.
Lumbsch HT, Elix JA. 2004. Lecanora. Flora of Australia 56A: 12–62.