Aspicilia phaea (dusky sunken disk lichen) is a grayish brown to tan areolate crustose lichen commonly found on rock in coastal to inland parts of central and southern California. Described as new to science in 2007,[1] [2] it is endemic to (only found in) California.[3] It grows on exposed or partially shaded siliceous rock, with a few known occurrences on serpentine rock.[2]
In rare cases full areolas do not form, and it appears as being cracked (rimose).[1] [2] There are often grayish or whitish spots on the areolas.[2] The thallus is 2–8 cm in diameter, and 0.1– 1.2 mm thick.[2] The areolas are irregularly sized and angular, giving the lichen body (thallus) the appearance of a mosaic of small polygons.[1] [2] A rim of dark tissue (prothallus) may surround the edges of the lichen.[1] [2] The fruiting body parts (apothecia) are flat to concave (especially in the thallus center), and slightly immersed in the thallus, appearing as sunken round to polygonal discs, often with a grey or white rim of thalline tissue.[1] [2] Lichen spot tests are all negative (K−, C−, KC−, P−).[1] [2]
The photobiont is a chlorococcoid.[2] In Joshua Tree National Park, it is commonly found to be infected with Lichenostigma, a genus or lichenicolous fungi (fungi that are parasitic on lichens).[3]