Althenia bilocularis
Synonyms
Lepilaena bilocularis Kirk
Family
Potamogetonaceae
Flora category
Vascular – Native
Endemic taxon
No
Endemic genus
No
Endemic family
No
Structural class
Herbs - Monocots
NVS code
The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.
LEPBIL
Current conservation status
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2017 using the New Zealand Threat Classification System (NZTCS). This report includes a statistical summary and brief notes on changes since 2012 and replaces all previous NZTCS lists for vascular plants. Authors: By Peter J. de Lange, Jeremy R. Rolfe, John W. Barkla, Shannel P. Courtney, Paul D. Champion, Leon R. Perrie, Sarah M. Beadel, Kerry A. Ford, Ilse Breitwieser, Ines Schönberger, Rowan Hindmarsh-Walls, Peter B. Heenan and Kate Ladley.
2012 | Threatened – Nationally Vulnerable | Qualifiers: RR, SO, Sp
Previous conservation statuses
2009 | At Risk – Naturally Uncommon | Qualifiers: SO
2004 | Sparse
Distribution
Indigenous. Known from North, South and Chatham Islands. Also present in Australia.
Habitat
Aquatic herb of lakes, brackish water, or slow-flowing rivers. Usually found in shallow fresh water habitats not far from the coast.
Features
Annual, summer-green, submerged, rhizomatous herb forming small patches. Stems up to 20 cm long, thread-like, usually unbranched. Internodes 1-4 cm long. Leaves regularly alternate, leaf-base at first sheathing stem, to 4 mm long, becoming fibrous with age, leaf-blade 2.5-3.5 x 1 mm, entire, 1- or 3- nerved, with nerves extending to the squarely truncate tip. Flower enclosed within leaf-bases. Both sexes in separate positions on the same plant. Male on small 5 mm stalk (pedicel), stamen solitary, anther 2 x 0.6 mm, sickle-shaped, with 2 pollen sacs. Female shortly stalked (pedicellate), perianth-segments narrow-oblong, lacerate, 1.5 x 0.5 mm. Carpels 3(-4), style narrower than ovary, stigma funnel-shaped with long feathery margins. Seed (achene) 1.5-2 x 0.5 mm., asymmetrically oblong, yellow, smooth, narrowing above to style remnant c. 1 mm long.
Similar taxa
Althenia is most likely to be confused with Zannichellia palustris which is a superficially similar indigenous aquatic herb of much the same habitats. Zannichellia differs from Althenia by its much-branched floating habit, in having leaves arranged in false whorls of 3-4, and by the flowers arranged together within the sheathing bracts. Submerged plants of Schoenus maschalinus (Cyperaceae) are also superficially similar, but these are much branched, and will not flower when submerged.
Flowering
Flowers can be present throughout the year
Fruiting
Fruit can be present throughout the year
Propagation technique
No information available.
Threats
As the result of field surveys it is clear that Althenia bilocularis is biologically sparse in its distribution. In the northern part of its range it seems to have been especially uncommon and there more than anywhere else is where it has undergone some range contraction. However, that loss is insufficient to justify its listing as Threatened.
Taxonomic Notes
Althenia bilocularis was initially placed in the genus Lepilaena, as L. bilocularis by Thomas Kirk who discovered it and described it (Kirk 1896). Later Cockayne (1927) placed Lepilaena bilocularis in Althenia, a decision that was not followed by Moore & Edgar (1970). Subsequently using a combination of molecular and morphological data Ito et al. (2016) confirmed the opinion of Cockayne (1927) and resurrected his combination in Althenia and this is followed here.
Attribution
Fact Sheet prepared for NZPCN by P.J. de Lange 14 April 2007: Description adapted from Moore and Edgar (1970).
References and further reading
Cockayne, L.C. in Speight, R., Wall, A. & Laing, R.M. (ed.) 1927: Ecological botany of the Canterbury Plains. Natural History of Canterbury: 126
Ito, Y.; Tanaka, N.; García-Murillo, P.; Muasya, A.M. 2016: A new delimitation of the Afro-Eurasian plant genus Althenia to include its Australasian relative, Lepilaena (Potamogetonaceae)–evidence from DNA and morphological data. Molecular Phylogenetics and Evolution 98: 261-270.
Kirk, T. 1896: Art. LII: Notes on Certain Veronicas, and descriptions of new species. Transactions and Proceedings of the New Zealand Institute 28: 500.
Moore, L.B.; Edgar, E. 1970: Flora of New Zealand. Vol. II. Government Printer, Wellington.
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Althenia bilocularis Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/althenia-bilocularis/ (Date website was queried)