''Posidonia robertsoniae'' is one of the

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 ...

, submerged flowering plants that occurs in the southern coastal waters.

Description

A species of ''

Posidonia ''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 ...

'', submerged flowering plants found in Mediterranean climates. A perennial

rhizomatous In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...

herb that appears as stands in marine habitat. This species is found at depths from 0.5 to 20 metres on white sands, in coastal waters that may be sheltered or subject to intense wave action. The habit of ''Posidonia robertsoniae'' is as a clumping stand, it is rhizomatous plant that puts out shoots with one or two leaves. The leaf blades are 2.5 to 4 millimetres wide, and 1.5 metres long. They are slightly leathery and uneven on the upper surfaces. Between 6 and 9 veins appear on each leaf. The flowering period is primarily during the months of August and September.

Distribution

''Posidonia robertsoniae'' is recorded at coasts of

Southwest Australia Southwest Australia is a biogeographic region in Western Australia. It includes the Mediterranean-climate area of southwestern Australia, which is home to a diverse and distinctive flora and fauna. The region is also known as the Southwest Aus ...

, from

Warnbro Sound Warnbro Sound, an Indian Ocean embayment, is located on the coast of Western Australia south of Cape Peron, 25 kilometres (16 miles) south of Fremantle. It is a semi-circular sound, wide with of shore. The area was surveyed in 1837 by Surveyor ...

Israelite Bay Israelite Bay is a bay and locality on the south coast of Western Australia. Situated in the Shire of Esperance local government area, it lies east of Esperance and the Cape Arid National Park, within the Nuytsland Nature Reserve and the Grea ...

Taxonomy

This species is contained by the

Posidoniaceae ''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 ...

family, one of eight occurring in southern Australia. The ninth member, ''

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 f ...

'', is found in the Mediterranean sea. The species was first described in ''

Aquatic Botany ''Aquatic Botany'' ("An International Scientific Journal dealing with Applied and Fundamental Research on Submerged, Floating and Emergent Plants in Marine and Freshwater Ecosystems") is a peer-reviewed scientific journal covering research on struc ...

'' in 1984, based on a

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

collected at

King George Sound King George Sound ( nys , Menang Koort) is a sound on the south coast of Western Australia. Named King George the Third's Sound in 1791, it was referred to as King George's Sound from 1805. The name "King George Sound" gradually came into use ...

in 1981.Kuo, J. & Cambridge, M.L. (1984) Aquatic Botany: 281, figs 3, 8a, 14, 22, 28, 32, 34a, 35b, 37c, 38c. Type: "HOLOTYPE: Western Australia, King George Sound, Albany, 8 m deep, 22 Dec., 1981, M.L. Cambridge & H.Kirkman Several related species within ''Posidonia'' are described as the ''Posidonia ostenfeldii'' complex, a group that may be in need of revision. The species ''

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 fro ...

'', which occurs in a wider distribution range, and this one may not be distinct, both lack evidence of genetic variation. The differing morphology of these species may be subject to environmental influence and their characters can overlap.

References

* * * {{Taxonbar, from=Q7233174 robertsoniae Angiosperms of Western Australia Monocots of Australia