Chiodecton pustuliferum Aptroot
Mycobank MB 17754
Thallus corticolous, crustose, pale brownish along the margins, whiter at the centre of the areoles, dull, consisting of ca. 0.4–4 mm diam crenate thallus areoles of irregular surface and outline on a continuous layer of brown arachnoid hypothallus that is underlying the whole thallus, covering areas of up to 7 cm diam, margins delimited by a continuous hypothallus, forming a line of up to 1 mm. Hypothallus filaments 2–3 µm wide, surface partly rough from crystals. Pustules numerous, erumpent, starting round, up to 3.0 mm diam and generally ca. 1.0 mm high, scarcely confluent, white (contrasting with the thallus), globular to irregular. Soredia formed inside the pustules, granular, ca. 100–200 µm diam, partly clustering into aggregates, internally formed of branched and gnarled hyphae with copious crystals. Algae trentepohlioid, cells ellipsoid, ca. 10 × 15 µm, identical in thallus and soredia. Apothecia and pycnidia unknown. Secondary chemistry: roccellic acid.
Chiodecton is a small genus in the family Roccellaceae characterized by stromatic ascomata with punctiform discs, superficially resembling the perithecial stromata of Trypethelium or other pyrenocarpous taxa (Thor, 1990). This species is the first Chiodecton to be described with pustules (Thor, 1990), and even in the order Arthoniales pustules were previously unknown. Although the material is sterile, the dull, yet not byssoid thallus on the arachnoid hypothallus and the presence of roccellic acid, make a classification in Chiodecton possible.
The epithet refers to the pustules.
The new species is only known from the type from primary tropical mountain forest at 950 m elevation in Madagascar.
Type:—MADAGASCAR: Tamatave: Périnet, Andasibe; 18º56’S, 48º16’E; May 1984, Aptroot & Hensen 13406 (holotype ABL).