Acarospora is a genus of lichenized fungi in the family Acarosporaceae. Most species in the genus are crustose lichens that grow on rocks in open and arid places all over the world. They may look like a cobblestone road or cracked up old paint, and are commonly called cobblestone lichens or cracked lichens,. They usually grow on rock, but some grow on soil (terricolous) or on other lichens. Some species in the genus are fungi that live as parasites on other lichens. Acarospora is a widely distributed genus, with about 128 species according to a 2008 estimate.
Acarospora socialis is a usually bright yellow aereolate to squamulose crustose lichen in the Acarosporaceae family that grows up to 10 cm wide, mostly on rock in western North America. It is among the most common lichens in the deserts of Arizona and southern California. It grows on sandstone, intrusive and extrusive igneous rock such as granitics, in all kinds of exposures to sunlight, including vertical rock walls. It is found in North America, including areas of the Mojave Desert and Sonoran Desert region, to Baja California Sur. It is the most common yellow member of its genus in southwestern North America. It sometimes, but rarely, grows on other soil crusts. It is a pioneer species.
Lecidea hassei is an endolithic lichen that appears as tiny black, gray rimmed, plate-like or crinkled discs between crystals of rock in California. The main body grows inside solid rock (endolithic), and the crinkled discs above the rock surface are the sexual reproduction structures. It is endemic to California, where it only grows in the lower montane belt, including in deserts and chaparral. It occurs in Joshua Tree National Park. The sexual reproduction structures (apothecia) are black, thinly rimmed with unpigmented fungal tissue surrounding black discs in the middle, and up to 2.2 mm in diameter. They rise out of the rock in a flat to convex disc with a constricted base, giving the appearance of tiny raised plates. It grows in open areas on granite, schist, and other acidic rock. It resembles Lecidea laboriosa but produces schizopeltic acid as a metabolite, instead of 4-O-demethyl planaic acid. The species epithet honors H.E. Hasse, who wrote the 1913 "Lichen Flora of Southern California". Lichen spot tests are negative on both the cortex and medulla.
Chrysothrix granulosa, the coastal gold dust lichen, is a brilliant yellow, powdery (leprose) lichen that grows in irregular patches mostly on bark in shaded dry areas of coastal western North America and western South America.
Lecanora muralis(Protoparmeliopsis muralis) is a waxy looking, pale yellowish green crustose lichen that usually grows in rosettes radiating from a center (placodioid) filled with disc-like yellowish-tan fruiting bodies (apothecia). It grows all over the world. It is extremely variable in its characteristics as a single taxon, and may represent a complex of species. The fruiting body parts have rims of tissue similar to that of the main nonfruiting body (thallus), which is called being lecanorine. It is paler and greener than L. mellea, and more yellow than L. sierrae. In California, it may be the most common member of the Lecanora genus found growing on rocks (saxicolous).
Aspicilia phaea 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, it is endemic to California. It grows on exposed or partially shaded siliceous rock, with a few known occurrences on serpentine rock.
Candelariella vitellina is a common and widespread green-yellow to orange-yellow crustose areolate lichen that grows on rock, wood, and bark, all over the world. It grows on non-calcareous rock, wood, and bark. It often has tiny lobate areoles in the shape of lion claws. The areoles may be flat or convex. Its sexual reproduction structures (apothecia) are a 0.35–1.0 mm-wide disc, darker yellow than the thallus, rimmed with thallus-like tissue lecanorine, flat but becoming convex with age. Lichen spot tests are K+ reddish, KC−, and C−. It produces calycin, pulvinic acid, pulvinic dilactone and vulpinic acid as secondary metabolites.
Heppia conchiloba is a gray to light brown squamulous to foliose terricolous lichen that occurs in southwestern deserts of North America. The surface appears as if covered in a light dust (pruinose). The squamules are peltate, up to 8 mm in diameter. There are one to several apothecia per lobe, with reddish-brown urn-shaped (urceolate) to concave discs, immersed so as to appear like concave spots. Lichen spot tests are all negative. Its entire thallus body is deeply convex, and it is different in color from other members of Heppia and or Peltula, which are olive or brownish-olive.
Acarospora strigata is an areolate to verruculous crustose lichen that grows on rock around the world, in full sun or shade, and in mesic to arid habitats. It is brown but may appear white or pale gray if it is covered in a pruina. The lichen is common in southwestern deserts of North America.
Lobothallia alphoplaca, the variable sunken disk lichen, is a creamy gray to brown, placoidioid areolate lichen that grows on rock in on rock and sometimes moss. It prefers growing on siliceous rocks. It is found in Europe, central Asia, and North America, where it grows in the southwestern deserts to central California. The center has numerous crowded and deformed apothecia with rims of thallus-like tissue (lecanorine). With dark reddish or grayish brown to black discs. Lichen spot tests on the thallus and apothecia are C−, and KC−, with tests on the cortex K+ red, P+ orange, or K−, P− and on the medulla K+ red, and P+ orange. It produces norstictic acid, constictic acid, or salazinic acid as secondary metabolites.
Acarospora elevata, the mountain cobblestone lichen, is a shiny dark reddish brown to dark brown verrucose to aereolate crustose lichen that grows up to 3 cm (1.2 in) wide on granite in central and southern California to Baja California, and high elevations in the Rocky Mountains. It is usually only found above 1,400 metres (4,600 ft) because it is eaten by red mites at lower elevations. In the Californias, it is mostly found at high elevations, but sometimes in coastal locations where it is less glossy. It grows in full sun, mostly on hard granite, but sometimes other igneous or carbonate rock, from 500 to 3,350 metres in elevation. It may start by growing on members of the genus Aspicilia, or other such pioneer species on hard rocks.
Acarospora fuscata is a glossy pale or yellowish-brown areolate lichen with angular areolas that grows up to 10 cm (4 in) wide on non-calcareous rock in low and high elevations. It grows in Europe and North America. It grows in southern California and on the eastern part of the Sierra Nevada range. It may grow with the areolas disconnected. The areolas may lift at the edges, but the areolas do not overlap like true squamules (sub-squamulose). More common in the Sierras is the similar species Acarospora thamnina, which is truly squamulose with overlapping scales.
Acarospora obnubila is a dull brown squamulose areolate crustose lichen that may grow up to 4 mm in diameter or with squamules scattered among other lichens. They are common in Arizona, southern California, and Baja California. They grow by themselves on acidic rock in full sunlight. Squamules measure up to 2 mm in diameter and are round to irregular, with have a stipe. They may also grow on members of the genus Aspicilia (lichenicolous). Competition for space with other lichens stimulates longer stipes to develop, whereby the squamules may overlay other lichens.
Acarospora schleicheri, the soil paint lichen, is a bleached to bright yellow areolate to squamulose lichen that commonly grows to 10 cm (4 in) on soil (terricolous) in arid habitats of southern California and Baja California, also in Europe and Africa. It produces rhizocarpic acid as a secondary metabolite, which gives it a yellow coloration and serves to protect it from the sun. Its lower surface is also yellow. It can be greenish when moist. Roundish, angular, or irregularly shaped squamules are 0.5–4 mm in diameter. There are 0–1 apothecia embedded in the thallus, with 0.4–1.2 mm roundish black to reddish-brown, or dark brown discs, which sometimes fill the areola so as to be lecanorine. It divides vegetatively on the soil. Asci are club shaped (clavate) and have 100 or more spherical to ellipsoid spores. Lichen spot tests are negative, and it is UV+ orange under ultraviolet light.
Acarospora thelococcoides is a pruinose verruculose (warty) crustose lichen that grows in patches up to 10 cm across that grows on soil (terricolous), especially soils made from decomposed granite. It grows from San Benito, California to Baja California, and inland to 930 metres (3,050 ft). Each roundish areole becomes more pruinose toward the top with has a single round apothecium that is immersed with a dark brown disc, so as to appear like a collection of white rings. This appearance gives it the common name, soil eyes lichen.
Acarospora veronensis is a medium brown to dark brown or black crustose lichen that grows up to 4 cm (1.6 in) wide. It is extremely variable in its growth forms, being verruculose, rimose, areolate, or squamulose. It has 0.2–1.5 mm round to angular areoles which may be lobed, and may be contiguous or dispersed. It grows on acidic rocks, basalt, and sometimes on wood. It is one of the most common members of its genus in the Sonoran Desert region, common in Arizona, southern California, Baja California north and south, Sonora, to outside the region in Durango. Each areole bears one to many 0.1–1 mm rounded to angular apothecia that are deeply immersed in the areole, with a dull reddish-brown flat to convex disc. Cylindrical asci have 100 or more ellipsoid ascospores. Lichen spot tests are all negative, and it is UV-. It is an indicator of undisturbed soil habitats. Sometimes specimens may look like Acarospora strigata.
Aspicilia cinerea is a gray to almost white, 1.5 – 15 cm wide, crustose areolate lichen with large apothecia that mostly grows on rock in the mountains. It grows in variable forms, from having a continuous surface to being areolate. It grows in Eurasia, and North America on siliceous rock, schist or igneous rock in habitats exposed to sunlight, also rarely on calciferous rock. It is common in Arizona, and rare in California and Baja California at elevations of 1,700 to 3,300 metres.
Aspicilia pacifica is a white to grayish, brownish, or ocher crustose areolate lichen that commonly grows on siliceous rock or basalt along the seashore and in higher coastal mountains of California and Baja California. It has numerous small (0.1–.8 mm), round to angular apothecia toward the middle of the thallus, with concave to flat black discs that are sometimes lightened with white pruina. Lichen spot test on the cortex and medulla are I−, K+ yellow to red, P+ orange, and C−. Secondary metabolites include much stictic acid, and some norstictic acid.
Bellemerea alpina, the brown sunken disk lichen, is a white to pale tan, thick crustose areolate lichen that grows on rock in the mountains worldwide. It grows in arctic-alpine habitats in Eurasia, North America, Australia, and New Zealand. Areoles are sometimes contiguous and sometimes dispersed. It often has very visible black prothallus. The brown to tan apothecia have a purplish tinge and are grayed by a pruinose coating, and embedded in the areoles, giving a similar appearance to members of the genus Aspicilia.
Buellia badia, the parasitic button lichen, is a dark chocolate-brown crustose areolate lichen of Europe, northern Africa, and North America that starts as a parasite growing on other lichens, such as Aspicilia phaea, gradually then becoming independent growing on rock (sometimes also on hardwood. Areoles may be contiguous or dispersed. Lecideine apothecia are 0.3 to 0.9 mm in diameter with black discs, that are initially flat, then become strongly convex as they age. Lichen spot tests are all negative. There are no known secondary metabolites as of. It is similar in appearance and other ways to the chocolate brown Dimelaena californica, which also starts off as a parasite on other lichens, and has spores of similar shape, size, and internal construction. D. californica has not been found on wood, is more preferential as to the lichens it starts growing on, and commonly has norstictic acid as a secondary metabolite. Some think they should be included in a new, third genus.
