Pertusaria rupicola
Pertusaria rupicola is a species of saxicolous crustose lichen belonging to the family Pertusariaceae. It is characterized by its thick, brain-like folded thallus that appears grey-greenish or yellow-green in colour. This organism produces distinctive wart-like fruiting bodies with black to pale yellow-brown openings. Native to the Mediterranean region, it grows primarily on steep, north-facing siliceous rock surfaces in well-lit but indirect sunlight environments. The species has experienced population declines following wildfires due to its slow growth rate. P. rupicola also serves as a host for the lichenicolous fungus species Lichenostigma rupicolae.
Description
Pertusaria rupicola has a thick thallus with a cracked- and to texture, resembling brain-like folds in well-developed specimens. The thallus typically appears grey-greenish or yellow-green in colour and lacks both soredia and isidia. The species produces fruiting bodies within fertile, lecanorine verrucae. These verrucae are rounded, measuring 1–3 mm in diameter, and are usually numerous and tightly arranged on the thallus surface. The margin of these structures is thick and smooth, matching the colour of the surrounding thallus. The hymenium often contains sterile areas.The ostioles are matt black to pale yellow-brown in colour. They initially appear as small dots but later develop into open structures reaching up to 1.5 mm in diameter. The lichen produces within asci, typically with eight spores per ascus. These ascospores have a distinctive double and smooth wall structure and measure 70–100 by 30–50 μm.
Chemical spot testing reveals that the thallus is K+, C+, KC+, and Pd+. The shows a red-violet reaction with K and C. The margin of the apothecia occasionally produces a red reaction with K, though this is rare. The secondary metabolites in P. rupicola include thiophaninic acid, stictic acid, norstictic acid, cryptostictic acid, and variably present compounds such as menegazziaic acid and atranorin.