Byssoloma xanthonicum
Byssoloma xanthonicum is a species of corticolous, crustose lichen in the family Pilocarpaceae. It is found in New Caledonia.
Taxonomy
The lichen was formally described by the Dutch lichenologist André Aptroot in 2014. The type specimen was collected near Farino in New Caledonia, at an elevation of about. Byssoloma xanthonicum is one of the few corticolous species within the genus Byssoloma.Description
Byssoloma xanthonicum has a thin, non-, and continuous thallus that is cream-coloured with a dull appearance. It is bordered by a thin brown line known as the. The algae within the thallus are . The species features apothecia, which are the fruiting bodies, measuring 0.2–0.6 mm in diameter. These apothecia are round but often in shape, with a flat, dull, dark brown that is not . The margin surrounding the disc is cream to chamois-coloured, dull, and has a felty texture, approximately 0.05 mm wide. The is 25–35 μm high, hyaline but becomes brownish at the base due to diluted pigment from the. The are branched. The is dark brown, coloured by a concentrated pigment. The is hyaline and composed of anastomosing hyphae approximately 3 μm wide. The is of the Pilocarpaceae-type, with a that reacts pale blue to iodine-potassium iodide staining and has a darker blue tube inside. Each ascus contains 8. These spores are hyaline,, 3-septate, measuring 11–13 by 2.5–3.5 μm, and are slightly constricted at the . were not observed in this species.The thallus of Byssoloma xanthonicum fluoresces a yellow-orange colour when lit with a ultraviolet light, owing to the presence of the compound lichexanthone. It additionally has a K+ reaction, a result of norstictic acid.