''Posidonia'' is a genus of

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

s. It contains nine species of marine plants ("

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

"), 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 east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern ...

and around the south coast of

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

. The

APG system The APG system (Angiosperm Phylogeny Group system) of plant classification is the first version of a modern, mostly molecular-based, system of plant taxonomy. Published in 1998 by the Angiosperm Phylogeny Group, it was replaced by the improved ...

(1998) and

APG II system The APG II system (Angiosperm Phylogeny Group II system) of plant classification is the second, now obsolete, version of a modern, mostly Molecular phylogenetics, molecular-based, list of systems of plant taxonomy, system of plant taxonomy that ...

(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. Perhaps the most important food cro ...

, in the clade

monocots Monocotyledons (), commonly referred to as monocots, ( Lilianae '' sensu'' Chase & Reveal) are flowering plants whose seeds contain only one embryonic leaf, or cotyledon. A monocot taxon has been in use for several decades, but with various ranks a ...

. The AP-Website concludes that the three families

Cymodoceaceae Cymodoceaceae is a family of flowering plants, sometimes known as the "manatee-grass family", which includes only marine species. The 2016 APG IV does recognize Cymodoceaceae and places it in the order Alismatales, in the clade monocots. The ...

, Posidoniaceae and

Ruppiaceae ''Ruppia'', also known as the widgeonweeds, ditch grasses or widgeon grass, is the only extant genus in the family Ruppiaceae, with 11 known species. These are aquatic plants widespread over much of the world. The genus name honours Heinrich Be ...

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 five genera. The largest genus in the family by far is '' Potamogeton'', ...

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

nitrogen fixation Nitrogen fixation is a chemical process by which molecular dinitrogen () is converted into ammonia (). It occurs both biologically and abiological nitrogen fixation, abiologically in chemical industry, chemical industries. Biological nitrogen ...

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 gen ...

'' Cambridge and Kuo *''

Posidonia australis ''Posidonia australis'', also known as fibre-ball weed or ribbon weed, is a species of seagrass that occurs in the southern waters of Australia. It forms large meadows important to environmental conservation. Balls of decomposing detritus from ...

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 20 years he served as director of the Ro ...

South coast of

. *''

Posidonia coriacea ''Posidonia coriacea'' 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 stands in marine habitat. This species is found at depths from ...

'' 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 gen ...

'' 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 gen ...

'' Kuo and Cambridge *''

Posidonia oceanica ''Posidonia oceanica'', commonly known as Neptune grass or Mediterranean tapeweed, is a seagrass species that is endemic to the Mediterranean Sea. It forms large underwater meadows that are an important part of the ecosystem. The fruit is free ...

'' ( 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 Napoleon ...

– This plant is

endemic Endemism is the state of a species being found only 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 foun ...

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 east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

, 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 they maintain an open character. Meadows can occur naturally under favourable con ...

s. *'' Posidonia ostenfeldii'' den Hartog *'' Posidonia robertsoniae'' Kuo and Cambridge *''

Posidonia sinuosa ''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 gen ...

'' Cambridge and Kuo The species described by

Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

, ''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 n ...

, 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 ...

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

Ibiza Ibiza (; ; ; #Names and pronunciation, see below) or Iviza is a Spanish island in the Mediterranean Sea off the eastern coast of the Iberian Peninsula. It is 150 kilometres (93 miles) from the city of Valencia. It is the third largest of th ...

which measured 8 km across and is 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''
{{Authority control Alismatales genera Taxa named by Charles Konig