Marcelaria benguelensis

The lichen was first formally described in 1885 by Swiss botanist Johannes Müller Argoviensis as a species of Bathelium. The type specimen was collected in India.[3] In 1922, Alexander Zahlbruckner transferred it to the genus Laurera.[4] The taxon was one of three species transferred to the newly circumscribed genus Marcelaria in 2013.[2]

The taxon Laurera subbenguelensis described in 1987 by Dalip Kumar Upreti and Ajay Singh from specimens found in Kerala,[5] was later determined to be synonymous with Marcelaria benguelensis.[2]

Marcelaria benguelensis has an olive-green, crustose thallus with a surface that often has an orange pruina. The ascomata resemble warts on the thallus surface; they are 0.6–1 mm in diameter, and cluster together in groups of 2 to 6. The ascospores, which number 8 per ascus, are muriform (divided into chambers) with 15 to 23 septa running transversely through the spore and 3 to 7 that are longitudinal; the spores measure 50–80 by 17–23 μm and have a gelatinous sheath that is 3–12 μm thick.[2]

Marcelaria benguelensis contains the secondary compounds parietin and teloschistin (both anthraquinone pigments) and lichexanthone. The latter substance causes the thallus to fluoresce a yellow colour when shone with a UV light.[2] Laboratory tests have shown that extracts of the lichen have antimicrobial properties, which are attributed to the presence of lichexanthone.[6]

The lichen has been recorded from Cambodia, India, Myanmar, the Philippines,[2] and Thailand.[6]