Halegrapha chimaera
Halegrapha chimaera is a species of script lichen in the family Graphidaceae. It forms a thin, whitish-grey crust on tree bark and produces black, elongated, slit-like fruiting bodies. The species is the type of its genus, Halegrapha, which was named in honour of the American lichenologist Mason Hale. It is known only from lower montane rainforest on Luzon in the Philippines.
Taxonomy
Halegrapha chimaera was formally described in 2011 by Eimy Rivas Plata and Robert Lücking, at the same time that they introduced the genus Halegrapha, with H. chimaera designated as the type species. The genus was dedicated to the American lichenologist Mason Hale, who had collected early material of the group and recognized its unusual combination of, but did not publish a description.The authors regarded Halegrapha as a morphological "chimera" within the Graphidaceae: it has the black, strongly, slit-like fruiting bodies typical of Graphis, yet it matches Phaeographis and close relatives in the structure of the hymenium and in having brown, transversely septate ascospores. DNA sequence data available for H. chimaera placed the genus within the broader Phaeographis lineage, while remaining distinct from other named genera treated in that group. In their original account, the authors compared H. chimaera with Graphis anfractuosa, which can look similar externally, but differs in having the typical Graphis spore type rather than the brown, Phaeographis-type spores seen in Halegrapha.
Description
The lichen forms a thin, continuous crust on bark, usually white to grey, with a smooth to slightly uneven surface. Individual thalli recorded in the type series were up to a few centimetres across. In cross-section, the thallus has a firm upper and an uneven containing the green alga Trentepohlia, with abundant crystals concentrated above and within the . The fruiting bodies are black that break through the thallus surface. They are typically unbranched or only sparsely branched, with the spore-bearing mostly concealed by thick, black lips that soon become distinctly striate.Microscopically, the lirellae have a laterally carbonized, and the hymenium is colourless but . Each ascus contains eight brown ascospores that are usually 3–5-septate and measure about 15–20 × 6–8 μm. The spores are typically ellipsoid, with the distal end often tapering slightly, and only rarely show an extra longitudinal septum. No lichen substances were detected for this species by thin-layer chromatography.