Rock Speckled Shield Lichen

Punctelia stictica has a light to dark brown upper thallus surface, covered with secondarily sorediate pseudocyphellae, and soredia that are granular to isidioid (somewhat resembling isidia, often darkened and solid looking, but with a cortex and typically arising from distinct soralia). The thallus underside is brown, darkening to black towards the centre. The lichen contains gyrophoric acid as the major medullary metabolite in the medulla, and conidia that are long and filiform (threadlike). A 1996 study compared the morphological and chemical differences between Punctelia stictica and Punctelia colombiana (another species with filiform conidia), concluding that the species are closely related but distinct, and are possibly derived from Punctelia jujensis.

Punctelia stictica is a widely distributed species. It has an antitropical distribution–a type of disjunct distribution where it occurs at comparable latitudes across the equator but not in the tropics. Although primarily temperate, its range extends into the European boreal zone. In North America, it has been recorded from the United States. In South America, it occurs in Colombia, Ecuador, Venezuela, Argentina, and Chile; it is very common in Patagonian steppe areas. In Europe it is known from France and Norway. In Africa, specimens have been collected from Ethiopia and Lesotho. It has also been found in west Greenland. The lichen is usually found growing on rocks, and infrequently on bark or on the ground.

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