''Posidonia'' is a genus of

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

s. It contains nine species of marine plants ("

seagrass Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the orde ...

"), found in the seas of the

Mediterranean The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...

and around the south coast of

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. The APG system (1998) and APG II system (2003) accept this genus as constituting the sole genus in the family Posidoniaceae, which it places in the order

Alismatales The Alismatales (alismatids) are an order of flowering plants including about 4,500 species. Plants assigned to this order are mostly tropical or aquatic. Some grow in fresh water, some in marine habitats. Description The Alismatales compri ...

, in the clade monocots. The AP-Website concludes that the three families Cymodoceaceae, Posidoniaceae and

Ruppiaceae ''Ruppia'', also known as the widgeonweeds, ditch grasses or widgeon grass, is the only extant genus in the family Ruppiaceae, with eight known species. These are aquatic plants widespread over much of the world. The genus name honours Heinrich ...

form a monophyletic group. Earlier systems classified this genus in the family

Potamogetonaceae The Potamogetonaceae, commonly referred to as the pondweed family, is an aquatic family of monocotyledonous flowering plants. The roughly 110 known species are divided over six genera. The largest genus in the family by far is ''Potamogeton'', w ...

or in the family Posidoniaceae but belonging to order Zosterales. ''Posidonia oceanica'' has

nitrogen fixation Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmo ...

capabilities via symbiosis and other species may as well.

Species

This is a list of species that are contained by the genus: *''

Posidonia angustifolia ''Posidonia'' is a genus of flowering plants. It contains nine species of marine plants ("seagrass"), found in the seas of the Mediterranean and around the south coast of Australia. The APG system (1998) and APG II system (2003) accept this ge ...

'' Cambridge and Kuo *'' Posidonia australis''

Hook.f. Sir Joseph Dalton Hooker (30 June 1817 – 10 December 1911) was a British botanist and explorer in the 19th century. He was a founder of geographical botany and Charles Darwin's closest friend. For twenty years he served as director of t ...

South coast of

. *'' Posidonia coriacea'' Cambridge and Kuo *''

Posidonia denhartogii ''Posidonia'' is a genus of flowering plants. It contains nine species of marine plants ("seagrass"), found in the seas of the Mediterranean and around the south coast of Australia. The APG system (1998) and APG II system (2003) accept this ge ...

'' Kuo and Cambridge *''

Posidonia kirkmanii ''Posidonia'' is a genus of flowering plants. It contains nine species of marine plants ("seagrass"), found in the seas of the Mediterranean and around the south coast of Australia. The APG system (1998) and APG II system (2003) accept this ge ...

'' Kuo and Cambridge *'' Posidonia oceanica'' ( L.)

Delile Alire Raffeneau Delile (23 January 1778, in Versailles – 5 July 1850, in Montpellier) was a French botanist. Biography Delile studied botany with Jean Lemonnier, and was in the Paris medical school in 1796. Egypt Delile participated in Napole ...

– This plant is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

, where it forms undersea

meadow A meadow ( ) is an open habitat, or field, vegetated by grasses, herbs, and other non-woody plants. Trees or shrubs may sparsely populate meadows, as long as these areas maintain an open character. Meadows may be naturally occurring or artifi ...

s. *''

Posidonia ostenfeldii ''Posidonia ostenfeldii'' is a species of seagrass that occurs in the southern waters of Australia. Description A species of ''Posidonia''. A perennial rhizomatous herb that appears as clumps on sand in marine habitat. It is found at depths be ...

'' den Hartog *''

Posidonia robertsoniae ''Posidonia robertsoniae'' is one of the seagrasses of Western Australia, submerged flowering plants that occurs in the southern coastal waters. Description A species of ''Posidonia'', submerged flowering plants found in Mediterranean climates. ...

'' Kuo and Cambridge *'' Posidonia sinuosa'' Cambridge and Kuo The species described by Linnaeus, ''Posidonia oceanica'', is found in the Mediterranean; the rest are located around the southern coast of Australia. Some species are endemic

seagrasses of Western Australia The Seagrasses of Western Australia are submerged flowering plants found along the coast, around islands, and in Estuaries of Western Australia. The region contains some of the largest seagrass meadows in the world, and is the most diverse in the nu ...

, all the Australian species are found in that region's diverse habitats. This arrangement was divided into two complexes: the ''Posidonia australis'' and ''Posidonia ostenfeldii'' groups. Some species descriptions may only be regional characteristics, and may need further revision. In 2006 a

clonal colony A clonal colony or genet is a group of genetically identical individuals, such as plants, fungi, or bacteria, that have grown in a given location, all originating vegetatively, not sexually, from a single ancestor. In plants, an individual in s ...

of ''P. oceanica'' was discovered south of the island of

Ibiza Ibiza (natively and officially in ca, Eivissa, ) is a Spanish island in the Mediterranean Sea off the eastern coast of the Iberian Peninsula. It is from the city of Valencia. It is the third largest of the Balearic Islands, in Spain. Its l ...

which measured 8 km across and possibly up to 100,000 years old.

Taxonomy

References

External links

*
Posidoniaceae
in L. Watson and M. J. Dallwitz (1992 onwards
The families of flowering plants

Flora Europaea: ''Posidonia''
{{Taxonbar, from=Q877147 Alismatales genera Taxa named by Charles Konig