A lichen is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship. Lichens are important actors in nutrient cycling and act as producers which many higher trophic feeders feed on, such as reindeer, gastropods, nematodes, mites, and springtails. Lichens have properties different from those of their component organisms. They come in many colors, sizes, and forms and are sometimes plant-like, but are not plants. They may have tiny, leafless branches (fruticose); flat leaf-like structures (foliose); grow crust-like, adhering tightly to a surface (substrate) like a thick coat of paint (crustose); have a powder-like appearance (leprose); or other growth forms.
Aspicilia is a genus of mostly crustose areolate lichens that grow on rock. Most members have black apothecia discs that are slightly immersed in the areolas, hence the common name"Given the same reason, the naming of Aspicilia is derived from the Greek word for "shield concave".
The Arthoniales is the second largest order of mainly crustose lichens, but fruticose lichens are present as well. The order contains around 1500 species, while the largest order with lichenized fungi, the Lecanorales, contains more than 14000 species.
Acolium is a genus of lichenized fungi in the family Caliciaceae. The genus has a widespread distribution and contains six species. These lichens are found on bark and wood, occasionally on rocks, or growing on other lichens.
Tetramelas is a genus of lichenized fungi in the family Caliciaceae.
Cetrelia is a genus of leafy lichens in the large family Parmeliaceae. They are commonly known as sea-storm lichens, alluding to the wavy appearance of their lobes. The name of the genus, circumscribed in 1968 by the husband and wife lichenologists William and Chicita Culberson, alludes to the former placement of these species in the genera Cetraria and Parmelia.
The Caliciaceae are a family of mostly lichen-forming fungi belonging to the class Lecanoromycetes in the division Ascomycota. Although the family has had its classification changed several times throughout its taxonomic history, the use of modern molecular phylogenetic methods have helped to establish its current placement in the order Caliciales. Caliciaceae contains 36 genera and about 600 species. The largest genus is Buellia, with around 300 species; there are more than a dozen genera that contain only a single species.
Lichens are symbiotic organisms made up of multiple species: a fungus, one or more photobionts and sometimes a yeast. They are regularly grouped by their external appearance – a characteristic known as their growth form. This form, which is based on the appearance of vegetative part of the lichen, varies depending on the species and the environmental conditions it faces. Those who study lichens (lichenologists) have described a dozen of these forms: areolate, byssoid, calicioid, cladoniform, crustose, filamentous, foliose, fruticose, gelatinous, leprose, placoidioid and squamulose. Traditionally, crustose (flat), foliose (leafy) and fruticose (shrubby) are considered to be the three main forms. In addition to these more formalised, traditional growth types, there are a handful of informal types named for their resemblance to the lichens of specific genera. These include alectorioid, catapyrenioid, cetrarioid, hypogymnioid, parmelioid and usneoid.
A spot test in lichenology is a spot analysis used to help identify lichens. It is performed by placing a drop of a chemical on different parts of the lichen and noting the colour change associated with application of the chemical. The tests are routinely encountered in dichotomous keys for lichen species, and they take advantage of the wide array of lichen products produced by lichens and their uniqueness among taxa. As such, spot tests reveal the presence or absence of chemicals in various parts of a lichen. They were first proposed by the botanist William Nylander in 1866.
Lobothallia is a genus of lichens in the family Megasporaceae. Species in the genus have foliose thalli that become crustose areolate in the center with age, and grow on calcareous to siliceous rocks. The crustose part of the body may keep its lower cortex, though not always. Dark brown to black apothecia may be sunken into the surface of the thallus, as indicated in the common name puffed sunken disk lichen. Members grow to 3–5 cm (1.2–2.0 in) or more radiating lobes (placodioid). The photobiont is green alga from the genus Trebouxia. The genus is represented in Eurasia, Asia, North Africa, Central America, western North America, and Australia.
Candelariella vainioana is a species of crustose lichen in the family Candelariaceae. It was described by Finnish lichenologist Rainar Hakulinen in 1954 from collections made by Edvard August Vainio in Hollola in 1874. The specific epithet vainioana honours Vainio. The lichen has been reported from Finland, Sweden, and Norway. The lichen's common name in Swedish is kopparägglav, and kuparikeltuaisjäkälä in Finnish, both of which mean "copper egg-yolk". As of 2019, it is considered to be an endangered species in Finland due to its small population.
Leif Tibell is a Swedish lichenologist and Emeritus Professor at the University of Uppsala. He is known for his expertise on calicioid lichens. He was awarded the Acharius Medal in 2012 for lifetime achievements in lichenology.
Circinaria caesiocinerea is a species of lichen belonging to the family Megasporaceae. It was first described as Lecanora caesiocinerea in 1869 by William Nylander, but was transferred to the genus Circinaria in 2010 by Anders Nordin, Sanja Savić, and Leif Tibell.
Paralecia is a monotypic fungal genus in the family Cladoniaceae. It contains a single species, the lichenicolous fungus Paralecia pratorum, found in Europe.
Circinaria calcarea is a species of crustose lichen in the family Megasporaceae. It was first described as a new species by Carl Linnaeus in his 1753 work Species Plantarum. Linnaeus named it Lichen calcareus, as he classified all lichens in the eponymously named genus. The species has had an extensive taxonomic history, resulting in dozens of synonyms. In 2010, it was placed in its current genus, Circinaria, following molecular phylogenetic analysis of the Megasporaceae.
Stereocaulon glareosum is a species of snow lichen belonging to the family Stereocaulaceae.
Tetramelas pulverulentus is a species of lichenicolous (lichen-dwelling) fungus in the family Caliciaceae. It was originally described as a new species by Martino Anzi in 1860. The type specimen was collected in Italy. Swedish lichenologists Anders Nordin and Leif Tibell transferred it to the genus Tetramelas in 2005 based on molecular phylogenetic analysis. It is closely related to Tetramelas phaeophysciae but differs from that species in its ascospores, which have three septa.
Dirina catalinariae is a species of saxicolous (rock-dwelling), crustose lichen in the family Roccellaceae. It occurs in the southwestern United States, Mexico, and the Galápagos Islands.
Vigneronia spieri is a species of corticolous (bark-dwelling), crustose lichen in the family Roccellaceae. It is found in the Galápagos Islands, mainland Ecuador and the Antilles (Curaçao).
