''Tetradesmus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...

in the family

Scenedesmaceae Scenedesmaceae is a family of green algae in the order Sphaeropleales. ''Scenedesmus'' algae are commonly found in freshwater plankton. The former family Coelastraceae is considered a synonym of Scenedesmaceae. The family has existed since at ...

. Species of ''Tetradesmus'' are found in a variety of habitats, including

fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salt (chemistry), salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include ...

and

biological soil crust Biological soil crusts, often abbreviated as biocrusts, are communities of living organisms inhabiting the surface of soils in arid and semi-arid ecosystems, which form stable aggregates of soil particles in a thin layer millimeters to centimeters ...

s in deserts.

Taxonomy

The genus ''Tetradesmus'' was described by

Gilbert Morgan Smith Gilbert Morgan Smith (6 January 1885, Beloit, Wisconsin – 11 July 1959) was a botanist and phycologist, who worked primarily on the algae. He was best known for his books, particularly the ''Freshwater Algae of the United States'', the ''Marin ...

, containing the single species '' Tetradesmus wisconsinensis''. It was not universally accepted;

Robert Hippolyte Chodat Robert Hippolyte Chodat (4 June 1865, Moutier – 28 April 1934) was a Swiss botanist and phycologist who was a professor and director of the botanical institute at the University of Geneva. He studied medicine and botany at Geneva, where he was ...

synonymized the genus into ''

Scenedesmus ''Scenedesmus'' is a genus of green algae, in the class Chlorophyceae. They are colonial and non-motile. They are one of the most common components of phytoplankton in freshwater habitats worldwide. Taxonomy The starting point of ''Scenedesmus'' ...

'', while

George Stephen West George Stephen West (20 April 1876 – 7 August 1919), ARCS, FLS, was a British botanist, a specialist in phycology and protistology, a botanical illustrator and a writer. With his father, botanist William West (West, 1848–1914), he colla ...

accepted the genus as separate from ''Scenedesmus''. In the 2000s, molecular data revealed found that ''Scenedesmus'' was

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

. ''Scenedesmus'' was subsequently split up into several genera, corresponding to the former

subgenera In biology, a subgenus ( subgenera) is a taxonomic rank directly below genus. In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the ge ...

''Scenedesmus'', ''Desmodesmus'', and ''Acutodesmus''. As ''Tetradesmus'' species are phylogenetically closely related to species once placed in ''Scenedesmus'' subgenus ''Acutodesmus'', the genus ''Acutodesmus'' was raised to genus rank and ''Tetradesmus'' was placed as a synonym of ''Acutodesmus''. However, since the name ''Tetradesmus'' was published before the genus combination ''Acutodesmus'' was made, this meant that the name ''Tetradesmus'' had priority Therefore, species in ''Acutodesmus'' were renamed to ''Tetradesmus''.

References

Sphaeropleales genera Sphaeropleales {{Chlorophyceae-stub