Thelotrema fijiense Lumbsch, Lücking & Naikatini
Mycobank MB 517814
Thallus epi- to hypophloedal, thin, whitish grey, pale olive to brown around ascomata. Thallus dull to shiny, smooth, continuous. Protocortex discontinuous, up to 20 µm thick. Algal layer continuous, crystals sparse, small. Vegetative propagules not seen. Ascomata 0.2–0.4 mm in diam., roundish, apothecioid, solitary to rarely marginally fused, semi-emergent to emergent, flattened-hemispherical. Disc often becoming partly visible, greyish to pale flesh-colored, slightly pruinose. Pores small, up to 0.25 µm in diam., roundish to slightly irregular, entire to slightly split, proper exciple apically visible from surface, whitish to off-white, incurved. Thalline rim margin thin, becoming wide to rarely gaping with age, roundish to irregular-roundish, entire, olive-brown to brown. Proper exciple becoming free, at least partly, hyaline to pale yellowish internally, yellowish brown marginally, amyloid at the base. Hymenium up to 140 µm high, clear, conglutinated, paraphyses moderately interwoven, unbranched to slightly branched, tips slightly thickened, lateral paraphyses present, inconspicuous, up to 30 µm long, columellar structures absent. Epihymenium hyaline to brown, granulose. Asci 8-spored, tholus thick narrowing at maturity. Ascospores transversely septate, cell walls thick, smooth, non-halonate, hyaline when young, becoming brown at maturity, faintly amyloid, fusiform, ends roundish to acute, loci angular to roundish, 19–27 x 5–7 µm with (7–)9–(11) septa. Pycnidia not seen. Secondary chemistry (HPTLC): no substances (all spot tests negative).
Thelotrema is a large genus of crustose, mostly tropical-montane lichens in Graphidaceae, characterized by apothecia with a double margin and periphysoids projecting from the excipulum (Frisch, 2006; Rivas Plata et al., 2010). Thelotrema fijiense is characterized by its whitish thallus with brown ascomata, and small, transversely septate ascospores that turn brown when mature. The species lacks secondary metabolites and is similar to T. subtile and T. suecicum (Lumbsch et al., 2008; Mangold et al., 2009). The latter differs in having larger ascospores that remain hyaline and less emergent ascomata that are concolorous with the thallus. Thelotrema subtile agrees with the new species in having ascospores that turn brown, but is readily distinguished by having ascomata that are concolorous with the thallus and larger, halonate ascospores with more or less crenate cell walls. A further species of the T. subtile-group that may be confused with T. fijiense is T. defossum (Lumbsch et al., 2008). This species, however, differs in having halonate, hyaline ascospores that never turn brown, and in having inconspicuous, immersed ascomata.
The name refers to the archipelago of Fiji, where the type was collected.
This new species is only known from the type locality in Taveuni Island (Fiji), where it grows on twigs in a cloud forest at 800 m altitiude.
Type:— FIJI: Taveuni Island, Access road to summit of Devo Peak; 16°51’S, 179°58’E; Apr 2008, Lumbsch 19813c (holotype SUVA; isotype F).
Additional specimens examined (paratypes):—None.
Sicut Thelotrema subtile sed ascomatis brunneis et ascosporis minutis differt.