Chapsa microspora Kalb
Mycobank MB 517750
Thallus corticolous, light grey to whitish, smooth, continuous, ca. 20–50 µm thick, dull, ecorticate to endoperidermal. Photobiont layer indistinct, 10–15 µm thick, with numerous photobiont cells and the inclusion of decomposed periderm cells and of a few small calcium oxalate crystals. Medulla endophloeodal. Apothecia erumpent to prominent, roundish, 0.6–1.2 mm in diam., usually 1–3 aggregate. Margin strongly raised, deeply fissured to lobed, upright to usually strongly recurved, with a thin, pale-grey to white-felty and sometimes slightly crystalline inner surface; proper exciple free. Disc pale brown, covered by a thin to rather thick white pruina. Periphysoids distinct, ca. 20 µm long. Hymenium 50–60 µm high, clear. Epihymenium unpigmented or partially greyish, ca. 5–8 µm high. Paraphyses simple, straight, 2–2.5 µm wide; tips indistinctly moniliform to occasionally branched, adspersed with fine greyish granules. Ascospores 6–8/ascus, 2–3 seriate, hyaline, with (2–)3 transverse septae, 7–9 × 4 µm, thick-walled, with rounded ends, I–. Pycnidia not seen. Secondary chemistry (TLC): stictic acid (major), constictic acid (major), hypostictic acid (trace) and hypoconstictic acid (trace).
Chapsa microspora is a conspicuous species being characterised by rather large roundish and aggregate apothecia with a clear hymenium, a free proper exciple, paraphyses with indistinctly moniliform or slightly branched tips and hyaline, transversely septate, small, non-amyloid ascospores with a well-developed endospore. The thallus is pale grey to whitish and contains substances of the stictic acid aggregate. C. aggregata (Hale) Sipman & Lücking from Dominica looks similar, but that species is distinctly corticate, without secondary lichen products, and has brown ascospores, ca. 16 × 8 µm. Chapsa albomaculata (Sipman) Sipman & Lücking also has aggregate apothecia, but the thallus is corticate and the ascospores are more septate with (4–)5–7(–8) septa, and the chemistry is slightly different [constictic acid (major), stictic acid (trace)]. Chapsa platycarpa (Tuck.) A. Frisch, another species with stictic acid aggr., has an epiperidermal, olive-green thallus with a prosoplectenchymatous cortex and brown ascospores. The same chemistry and a similar habitus as C. microspora, together with a free exciple, is found in Thelotrema porinoides Mont. & Bosch, but that species differs by large, multiseptate, I+ violet ascospores. Another species of Chapsa with very small (4.5 × 2.5 µm) and I– ascospores, namely C. bicellularis Sipman & Lücking, has a clear hymenium too, but differs in the absence of secondary lichen products and the hardly discernable thallus.
The epithet refers to the relatively small ascospores.
Chapsa microspora is known from a single but ample collection from a more or less virgin tropical rainforest in the Amazon basin. It was collected from the smooth and slightly decaying bark of an old deciduous tree in a rather shady situation.
Type:—BRAZIL. Amazonas: Rainforest along Rio Negro, 150 km upstream Manaus; 02°30’S, 61°10’W, 40 m; Oct 1980, Kalb s.n. (holotype hb. Kalb 26934).
Additional specimens examined (paratypes):—None.
Similis Chapsae aggregatae sed differt thallo non corticato, ascosporis minoribus, hyalinis et materia chemica.