Pseudopyrenula guianensis
Pseudopyrenula guianensis is a species of corticolous, crustose lichen in the family Trypetheliaceae. It is known from lowland rainforest in northern South America, with records from French Guiana and Suriname.
Taxonomy
The species belongs to the Pseudopyrenula subgregaria group. It is distinguished within that assemblage by two features used by lichenologists for identification: a clear but oil-dotted internal matrix and the presence of the fluorescent compound lichexanthone in the thallus. The type collection was made in 1986 near Saül, French Guiana.Description
The thallus is thin, whitish and . Sexual fruiting bodies are produced singly; they are black, hemispherical, and 0.3–0.5 mm in diameter, each with a tiny pore at the top. Inside, the hamathecium is colourless but contains scattered oil droplets. The ascospores are colourless, divided by three cross-walls, and measure 21–25 × 6–9 μm; they are smooth-walled and show diamond-shaped internal cavities formed by thickening of the inner spore wall.The thallus is UV-positive yellow under long-wave ultraviolet light, indicating lichexanthone; thin-layer chromatography confirms this compound.