Myriospora smaragdula forms a thallus composed of scattered to contiguous areoles, usually 0.6–1.7 mm in size. The areoles are flat to slightly convex and whitish, greyish white to pale brown. On copper-rich substrates, they may be yellowish green. Each areole usually contains 2–7 small, punctiform and permanently immersed apothecia with brown to dark brown discs. The cortex contains a continuous layer of norstictic acid crystals; in section, it reacts K+ red, producing conspicuous red needle-shaped crystals.
The species grows on acidic, usually slightly base-rich or nutrient-enriched siliceous rocks, for example on boulders, stone walls and masonry. It occurs in open to somewhat shaded habitats and may colonize copper-rich rocks, whereas it apparently avoids substrates with a high iron content. It is known from Europe and North America and is most frequently reported from northern Europe. Its distribution in the Czech Republic is insufficiently known, and older records require revision because several species now recognized as distinct were formerly included under the name Acarospora smaragdula. The only reliable Czech record is from Měděnec in the Krušné hory Mountains.
The most similar species is M. myochroa, which differs in having larger and more strongly convex areoles and, at maturity, broader apothecia with an uneven disc. Its reaction with KOH may not produce red needle-shaped crystals, and low concentrations of norstictic acid can sometimes be detected only by TLC.
Literature: Westberg M., Crewe A. T., Purvis O. W. & Wedin M. (2011): Silobia, a new genus for the Acarospora smaragdula complex (Ascomycota, Acarosporales) and a revision of the group in Sweden. – Lichenologist 43: 7–25.
taxonomic classification:Ascomycota → Lecanoromycetes → Acarosporales → Acarosporaceae → Myriospora
most frequented synonyms:Acarospora smaragdulaAll records: 33, confirmed 1. One click on a selected square displays particular record(s), including their source(s).