Rhizocarpon lecanorinum
Common name
Crescent-moon lichen
Family
Rhizocarpaceae
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 yellow, crescent-shaped areolae, often enclosing prominent apothecia; a red-brown epithecium; a pale greenish blue hymenium; 8-spored asci; and colourless to greenish or brown-black, submuriform ascospores.
Apothecia surrounded by crescent-shaped areolae; thallus K+ yellow, Pd+ orange (stictic acid).
Distribution
North Island: Wellington (Taranaki Falls, Mt Ruapehu). South Island: Canterbury (Waimakariri old riverbeds, Hakataramea Valley), Southland (S Mavora Lake).
Known also from Great Britain, Europe, Scandinavia, the high-Arctic, Turkey, and North America.
Habitat
On dry, exposed, sunny rock outcrops in grassland.
Associating with Buellia dunedina, B. stellulata, Candelariella vitellina, Diploschistes gyrophoricus, Immersaria athroocarpa, Lecanora rupicola, Lecidea fuscoatrula, Rhizocarpon geographicum, R. grande, R. submodestum and brown and yellow species of Xanthoparmelia.
Detailed description
Thallus areolate, in spreading patches, 5–10(–25) mm diam., often coalescing into much larger composite colonies. Prothallus distinct, black, at margins and between areolae. Areolae contiguous, 0.5–1.5 mm diam., mostly crescent-shaped, each segment partly to entirely surrounding an apothecium, to angular or orbicular with or without a central apothecium; flat to subconvex, smooth, bright-yellow to greenish yellow, epruinose. Apothecia frequent, rounded, 0.1–1 mm diam., plane to subconvex. Proper exciple persistent but indistinct, concolorous with disc. Epithecium pale red-brown, 7–15 μm thick. Hymenium pale greenish blue, 100–115 μm tall. Hypothecium intense dark-brown, opaque. Asci globose, 8-spored, 75–85 × 35–45 μm. Ascospores ellipsoidal to somewhat curved, submuriform, slightly constricted at septa, with 8–24 (–28) cells in optical section, colourless at first soon becoming dark-greenish to brown-black, 27–45 × 11–19 μm.
Chemistry: Thallus and medulla K+ yellow, C+ red or −, Pd+ orange, I+ blue; containing rhizocarpic and stictic acids, and occasionally also gyrophoric acid.
Similar taxa
It is chemically distinct from R. geographicum, as it contains stictic acid (K+ yellow, Pd+ orange), rather than psoromic acid (K−, Pd+ yellow). The shape of the areoles (which are crescent-shaped in R. lecanorinum) also separates the two species.
Substrate
Saxicolous
Attribution
Fact sheet prepared by Melissa Hutchison (31 December 2021). Brief description, Distribution, Habitat, Features, and similar taxa sections copied from Galloway (2007).
References and further reading
Galloway D.J. 2007: Flora of New Zealand: Lichens, including lichen-forming and lichenicolous fungi. 2nd edition. Lincoln, Manaaki Whenua Press. 2261 pp.