Wirthiotrema xanthopustulatum

Wirthiotrema xanthopustulatum is a species of corticolous (bark-dwelling) lichen in the family Graphidaceae. Found in Brazil, it was formally described as a new species in 2021 by lichenologists André Aptroot and Maria Fernanda de Souza. The type specimen was collected in Tagaçaba Porto da Linha (Guaraqueçaba, Paraná) on tree bark. It has a pale olivaceous, shiny metallic-green thallus that covers an area up to 10 cm in diameter. It contains the secondary compounds protocetraric acid and lichexanthone. This latter compound causes the lichen thallus to fluoresce a yellow colour when shone with a long-wavelength UV light. Wirthiotrema santessonii is similar in appearance, but it contains stictic acid rather than protocetraric acid and lichexanthone.