Astrothelium muriconicum Aptroot & M.F.Souza, 2021

Aptroot, André & Souza, Maria Fernanda, 2021, New lichen species and records from the Chapada dos Guimarães, Mato Grosso, Brazil, Cryptogamie, Mycologie 20 (10), pp. 171-180 : 173

Astrothelium muriconicum Aptroot & M.F.Souza , sp. nov.

( Fig. 1 )

Corticolous Astrothelium similar to A. cinnamomeum (Eschw.) Müll. Arg. in the ascomata with fused ostioles, pseudostroma orange, K+ red, but differing by the muriform ascospores of 50-55 × 12-14 µm.

MYCOBANK. — MB 839652.

TYPE. — Brazil, Mato Grosso, Cuiabá, Chapada dos Guimarães , Pousada do Parque private area, alt. 700 m, 15°26’50”S, 55°49’50”W, on bark, 12-19.IX.2020, A.Aptroot & M.F.Souza 81980 (holo-, CGMS; iso-, ABL).

DESCRIPTION

Thallus smooth, somewhat glossy, bullate, olivaceous green, surrounded by a 0.3 mm wide, firm and thick, black prothallus. Pseudostromata dull, pale orange yellow, irregular in shape, starting as angular areas of up to c. 1.5 mm, but partly laterally fusing, only slightly raised above the bullate thallus, between the thallus bullae, occupying about half of the thallus. Ascomata pyriform, c. 0.4-0.6 mm diam., immersed in pseudostromata, in groups of 2-6. Ostioles apical, fused, brown to black, 0.1-0.2 mm diam. Hamathecium not inspersed. Ascospores 8/ascus, hyaline, regularly muriform, 50-55 × 12-14 µm, fusiform, not constricted at the primary septum which is not markedly thickened, not surrounded by a gelatinous sheath. Pycnidia copious, black, c. 0.2 mm diam., erumpent from the pseudostromata, without conidia.

CHEMISTRY. — Thallus UV-, K-; pseudostromata UV+ red. With anthraquinone.

ETYMOLOGY. — Named after the muriform ascospores and belonging to the conicum -group.

ECOLOGY AND DISTRIBUTION. — On tree bark in Cerrado forest; only known from Brazil.

DISCUSSION

This is the first species in the Astrothelium conicum Eschw. group (the core group of the genus, characterized by fused eccentric ostioles and yellow to orange pigments externally on the pseudostromata) with muriform ascospores; it would key out in the world key by Aptroot & Lücking (2016) in group 7 at couplet 15: Ascomata with fused ostioles (astrothelioid), orange pigment on the pseudostromata only.

Figures

FIG. 1. — Astrothelium muriconicum sp.nov.,holotype,habitus.A, in daylight;B, under 365 nm UV light.Width of pictures 30 mm.