Halegrapha redonographoides
Halegrapha redonographoides is a species of bark-dwelling script lichen in the family Graphidaceae. It forms a cream-coloured to beige crust on tree bark and produces curved, slit-like fruiting bodies that are sunken into the thallus surface. The species was described in 2017 from northeastern Brazil, where it occurs in Caatinga dry forest and transitional Cerrado vegetation. It is one of the few members of its genus known to contain norstictic acid.
Taxonomy
Halegrapha redonographoides was described as a new species by Jaciele de Oliveira Dantas, Robert Lücking, and Marcela Cáceres. The type material was collected in Brazil from tree bark in a Caatinga vegetation remnant at Fazenda Santa Maria da Lage, near Poço Verde, at about elevation.The authors placed the species in the genus Halegrapha because it combines a pale, crystal-rich, Graphis-like thallus and thick, carbonized with small brown spores. The epithet redonographoides refers to its Redonographa-like look, especially the somewhat arrangement of the immersed lirellae, although it differs from Redonographa in being bark-dwelling and in having brown ascospores. In the protologue it was separated from the similar Halegrapha mucronata by its ecorticate thallus, the immersed lirellae, a completely carbonized excipulum, and small, somewhat ascospores. It also contains norstictic acid, a chemistry otherwise reported for only a small number of Halegrapha species.
Description
The lichen forms a crust on bark, typically across, with a rough, uneven surface that is cream-colored to beige. In cross-section the thallus is about 100–200 μm thick and lacks a well-developed . The algal partner is Trentepohlia, and the is irregular and broken up by large clusters of crystals.The fruiting bodies are slit-like apothecia that are usually unbranched and curved, and they are sunken into thicker parts of the thallus that can resemble low pseudostromata. The is concealed, while the are distinct, entire, and gray-black. Internally, the is black and completely carbonized, and the hymenium is clear and colorless. The asci are and eight-spored. Mature ascospores are brown, broadly ellipsoid, and somewhat muriform, measuring about 10–15 × 6–10 μm, and they give an I+ staining reaction when mature. Chemical tests and thin-layer chromatography indicate norstictic acid as the major lichen substance ; sections show a K+ reaction that produces red, needle-like crystals.