''Aquacidia'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

in the family

Pilocarpaceae The Pilocarpaceae are a family of crustose lichens in the order Lecanorales. The species of this family have a cosmopolitan distribution and have been found in a variety of climatic regions. Pilocarpaceae was circumscribed by Alexander Zahlbruck ...

. It has three species, which occur in Europe and North America. The genus was

circumscribed In geometry, the circumscribed circle or circumcircle of a polygon is a circle that passes through all the vertices of the polygon. The center of this circle is called the circumcenter and its radius is called the circumradius. Not every polyg ...

in 2018 by

André Aptroot André Aptroot (Heemskerk, 1961) is a Dutch mycologist and lichenologist. In 1993 he did his PhD at the University of Utrecht under the supervision of Robbert Gradstein (nl). His dissertation was titled "Systematic studies on pyrenocarpous li ...

to contain a small group of ''

Bacidia ''Bacidia'' is a genus of lichen-forming fungi in the family Ramalinaceae. The genus was circumscribed by Giuseppe De Notaris in 1846. Species in the genus are crust-like lichens with stemless apothecia; they have green algae (chloroccoid) as p ...

'' species that formed a distinct

lineage Lineage may refer to: Science * Lineage (anthropology), a group that can demonstrate its common descent from an apical ancestor or a direct line of descent from an ancestor * Lineage (evolution), a temporal sequence of individuals, populati ...

in the Pilocarpaceae. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

is '' Aquacidia trachona'', a lichen that was originally described in 1803 by Erik Acharius as ''Verrucaria trachona''. The genus name ''Aquacidia'' refers to the habitat of the species, which is typically on rocks near water. Lichens in this genus can form

thalli Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms were ...

that cover vast areas of substrate. For example, in Holland, the lichens can form large

colonies In modern parlance, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the '' metropolitan state'' ...

in sheltered rock crevices between boulders in

dikes Dyke (UK) or dike (US) may refer to: General uses * Dyke (slang), a slang word meaning "lesbian" * Dike (geology), a subvertical sheet-like intrusion of magma or sediment * Dike (mythology), ''Dikē'', the Greek goddess of moral justice * Dikes, ...

Species

*'' Aquacidia antricola'' *'' Aquacidia trachona'' *'' Aquacidia viridifarinosa''

References

Pilocarpaceae Lichen genera Lecanorales genera Taxa described in 2018 Taxa named by André Aptroot {{Lecanorales-stub