Acarospora is a genus of mostly lichen-forming 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 janae is a species of lichen in the Acarosporaceae family. Described as new to science in 2011, it is known only from New Mexico and Colorado in the United States, where it grows on siliceous rock.
Calopadia cinereopruinosa is a species of corticolous (bark-dwelling) lichen in the family Pilocarpaceae. Found in the Galápagos Islands, it was described as new to science in 2011. It is characterized by its grey-black, white-pruinose apothecia and aeruginous hypothecium. This lichen usually grows on the bark of stems and twigs in the humid zones of the islands.
Crustose lichens are lichens that form a crust which strongly adheres to the substrate, making separation from the substrate impossible without destruction. The basic structure of crustose lichens consists of a cortex layer, an algal layer, and a medulla. The upper cortex layer is differentiated and is usually pigmented. The algal layer lies beneath the cortex. The medulla fastens the lichen to the substrate and is made up of fungal hyphae. The surface of crustose lichens is characterized by branching cracks that periodically close in response to climatic variations such as alternate wetting and drying regimes.
Acarospora socialis is a usually bright yellow areolate to squamulose crustose lichen in the family Acarosporaceae 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.
Pleopsidium flavum is a distinctively colored, bright lemon-yellow to chartreuse crustose lichen that grows in high elevations on vertical or overhanging hard felsic rock in western North America. Its thallus grows in a circular outwardly radiating pattern (placodioid), with 1mm wide lobed edges. This is the identity of the vivid, lime-green lichens often photographed on granite boulders in the Wichita Mountains Wildlife Refuge of Oklahoma. According to Prof. Wayne Armstrong of Mount Palomar College, This lichen only grows "a few millimeters" per century., making it the slowest growing of all known plants.
Circinaria arida is a 0.5–6 cm, light olive-brown custose lichen that grows on rock, often like a cluster of little light brown to olive balls growing on pebbles, in the southwestern deserts of North America. It is also found in Eurasia, and arid parts of North America from the southern Great Plains and Midwest to California. It is warty (verrucose) with the warts sometimes cracking apart areolate. The warts or areolas have angular to rounded sides. The 0.2-2.3 mm, convex to flat-topped areolas are separated by deep fissures that may be as deep (0.1–2 mm) as the areaola is wide, so the lichen often appears to be made of clusters of little balls crammed up next to each other, although the areolas are sometimes isolated. In California it is commonly found growing on pebbles. Each areola has a single sunken black, dust covered (pruinose) fruiting body (apothecium) with a white rim. A thin strip of prothallus sometimes is at the outer edge, forming a narrow dark zone (fimbriate). The similar Aspicilia desertorum has a white pruina on the apothecia. It is negative for lichen spot tests, I−, K−, P−, C−.
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.
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 thamnina is a shiny, black tinged, variously brown squamulose crustose lichen. It has a linear growth pattern, growing along cracks in boulders. It can be found in North America to Alaska and Maine, from the coast to inland locations, also in the Ural Mountains and Novaya Zemlya in Russia. It commonly grows either among, or on other lichens. It grows a longer stipe so its squamules can grow over other lichens when there is competition for space. When it forms thick clumps it is easily identified with its elevated squamules and thick stipes. It grows on acidic rock in full sunlight.
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 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.
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.
Pleopsidium chlorophanum is a distinctively colored, bright lemon-yellow to chartreuse crustose lichen, which favors dry arctic or alpine sandstone cliffs and boulders. It is a rare alpine lichen in Europe. It is in the genus Pleopsidium of the family Acarosporaceae.
Acarospora bullata, commonly known as cracked lichen, is a species of lichen in the Acarosporaceae family. The British Lichen Society wrote in 2010 that Acarospora bullata, when seen in North America, has been described as conspecific to Acarospora rugulosa. This species is also known to be conspecific with Acarospora subcastenae and Acarospora mendozana.
Acarospora pseudofuscata is a species of saxicolous (rock-dwelling) crustose lichen in the family Acarosporaceae. It occurs on a few islands in the Aegean Sea and in Turkey.
Sarcogyne brunnea is a species of saxicolous and terricolous, crustose lichen in the family Acarosporaceae. It is found at high altitudes in arid regions of the Andes, growing on volcanic rock and soil. It has an areolate and densely pruinose brown thallus.
