About Acarospora fuscata (Ach.) Arnold
Acarospora fuscata, commonly called brown cobblestone lichen, is a glossy areolate lichen that ranges in color from pale brown to yellowish brown. It forms angular areolas, and may grow with disconnected areolas. Areola edges can lift upward, but the areolas do not overlap like the true squamules of fully squamulose lichens, so this species is considered sub-squamulose. This lichen can reach up to 10 centimeters (4 inches) wide, and it grows on non-calcareous rock at both low and high elevations. It is distributed across Europe and North America, and can be found in southern California and the eastern portion of the Sierra Nevada mountain range. The similar species Acarospora thamnina, which is truly squamulose with overlapping scales, is more common than Acarospora fuscata in the Sierras. Acarospora fuscata usually produces 0 to 1 apothecium per areole. Apothecia may be point-like (punctiform), or they can fill the entire areole with a rough-surfaced, reddish brown disc. Its asci are club-shaped (clavate) and contain more than 100 spores. Lichen spot tests for this species produce the following results: K negative, C weakly positive for a faint pink color, KC positive for a red color, and P negative. The secondary metabolite produced by this lichen is gyrophoric acid.
