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, in the clade
monocots. The AP-Website[4] concludes that the three families
Cymodoceaceae, Posidoniaceae and
Ruppiaceae form a monophyletic group. Earlier systems classified this genus in the family
Potamogetonaceae or in the family Posidoniaceae but belonging to order
Zosterales.
Posidonia oceanica has
nitrogen fixation capabilities via symbiosis and other species may as well.[5]
Species
This is a list of species that are contained by the genus:[6]
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, 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.[10] Some species descriptions may only be regional characteristics, and may need further revision.[6][11]
In 2006 a
clonal colony of P. oceanica was discovered south of the island of
Ibiza which measured 8 km across and is possibly up to 100,000 years old.[12]
Taxonomy
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^Cambridge, M.L. and Kuo, J. (1979) Two new species of seagrass from Australia, Posidonia sinuosa and Posidonia angustifolia (Posidoniaceae). Aquat. Bot. 6, 307–328 f. Keulen
^Kuo, J. and Cambridge, M.L. (1984) A taxonomic study of the Posidonia ostenfeldii complex (Posidoniaceae) with descriptions of four new Australian seagrasses. Aquat. Bot. 20, 267–95. f. Keulen
^den Hartog, C. (1970) Seagrasses of the World. Verh. Kon. Ned. Akad. Wetens. Afd. Naturk. Ser. 2 59:139 f. Keulen
^Kuo, J. and McComb, A.J. (1989) In: "Biology of Seagrasses. A treatise on the biology of seagrasses with special reference to the Australian region." (Eds. A.W.D. Larkum, A.J. McComb, S.A. Shepherd) (Aquatic Plant Studies 2) (Elsevier, Amsteredam). p. 6-73 f. Keulen