RAMONIA ¹

Gintaras Kantvilas ²

Ramonia Stizenb., Ber. Tätigk. St. Gallischen Naturwiss. Ges. 1861/1862: 168 (1862).

Type: R. valenzueliana (Mont.) Stizenb.

Thallus crustose, effuse, sometimes immersed in the substratum; prothallus absent. Photobiont Trentepohlia, with cells ± globose, 6–10 µm wide, crowded together or in short chains. Ascomata apothecia, at first immersed in the thallus, later erumpent, sessile, urceolate, with a strongly incurved exciple with a central pore overtopping the hymenium and obscuring a concave, pale pink to pale grey disc. Proper exciple at length becoming radially split, in section cupulate, hyaline to brown, composed of rhomboidal or subglobose, parenchymatous cells 3–7 µm wide and lined along the inner edge with periphyses. Hymenium hyaline, KI+ blue. Paraphyses simple, sometimes capitate. Asci narrowly cylindrical to clavate, (2–)8–many-spored, of the Gyalecta-type, with a thin, KI+ blue wall and a non-amyloid, poorly developed tholus. Ascospores simple, transversely septate or muriform, oblong, fusiform to ellipsoid, hyaline, thin-walled, with a gelatinous perispore. Conidiomata unknown. Chemistry: nil.

A genus of about 20 species, found mostly in tropical and oceanic temperate areas. It usually grows on bark but also has representatives on soil and rock. One species has been recorded in Tasmania. The radially split exciple is suggestive of the genus Topeliopsis, which also has urceolate apothecia, simple paraphyses, transversely septate or muriform ascospores and a Trentepohlia photobiont. However, Topeliopsis differs chiefly by having a non-cellular exciple of prosoplectenchymatous hyphae, non-amyloid, Thelotrema-type asci, and amyloid ascospores. The distinctly cellular exciple of Ramonia, in combination with the Gyalecta-type asci and Trentepohlia photobiont, also distinguish this genus from other gyalectoid lichens such as Absconditella, Cryptodiscus and Gyalecta. Coppins (1987) reported a minute, amyloid ring-structure in the ascus apex of some Ramonia species, which suggests the genus may be heterogeneous.

Key references: Vězda (1966); Coppins (1987); Sanderson & Purvis (2009).

1 Ramonia absconsa (Tuck.) Vězda

Folia Geobot. Phytotax. Bohemoslov. 1: 162 (1966); —Gyalecta absconsa Tuck., Proc. Amer. Acad. Arts Sci. 5: 414 (1862).

Thallus effuse, very thin and patchy, pale grey-green. Ascomata 0.3–0.5 mm wide, at first immersed or semi-immersed and visible as a “bump” on the thallus, pierced by a minute central pore with a grey rim, emergent when mature, becoming globose to hemispherical, with a dark brown, strongly incurved, radially split proper exciple, and the central pore to c. 0.15 mm wide, revealing a pale grey, urceolate disc. Exciple in section 40–70(–100) µm thick laterally, reddish brown at the upper and outer edges, hyaline within, at the base c. 20 µm thick and poorly differentiated from the subhymenium; periphyses 5–10 × 2–3 µm. Subhymenium hyaline, 10–25 µm thick. Hymenium 100–120 µm thick, weakly KI+ blue; paraphyses 1–1.5 µm thick, not capitate; asci 32-spored, 95–118 × 12–22 µm, narrowly cylindrical to clavate but sometimes bulging centrally when the spores are mature. Ascospores (12–)13–15.6–19(–20) × 5–5.5–6.5(–7) µm, 3(–5)-septate, ellipsoid, blunt or acute at the apices; perispore usually swelling in K.

Extremely rare in Tasmania and known from a single collection from the papery bark of an old Melaleuca ericifolia in a lowland, coastal swamp. Prior to this collection, it was known only from the type specimen, collected in the 19th Century from the bark of maple in South Carolina. The Tasmanian specimen matches published descriptions very well. A second species of Ramonia, R. leptospora (Müll.Arg) Vězda, has been described from temperate Australia (Victoria) but differs by having smaller 3-septate ascospores, 11–14 × 2.5 µm, occuring 6–8 per ascus.

Cape Portland, Musselroe Wind Farm, Tregaron Lagoons, 40°46'55"S 147°58'09"E, 2 m, 2019, G. Kantvilas 230/19 (E, HO).

References