Class
Family
Genus
Classification
Nomenclature
Scientific Name:
Trithuria inconspicua Cheeseman, Man. New Zealand Fl. 756 (1906) subsp. inconspicua
Description
Tufted 15–55 mm in height. Apomictic or sexual, plants in populations often female only, or plants cosexual with unisexual or bisexual reproductive units. Leaves 14–55 × 0.25–0.4 mm. Reproductive units 1–4 per tuft, on scapes 20–40 × 0.3–0.4 mm; involucral bracts 2–4(–5) ovate to narrow-ovate. Male reproductive unit bracts 3.5–5.0 mm long; stamens (1–)3–8; anthers 0.8–1.4 mm long, bright red, filaments 1–5 mm long. Bisexual reproductive unit bracts 4–5 mm long; stamens 1–5; carpels 2–10. Female reproductive unit bracts 2.5–5.0 mm long; carpels 8–24, reddish, with 5–13 stigmatic hairs of unequal length, 0.3–1.0 mm long, red becoming hyaline. Fruits 0.4–0.56 × 0.2–0.4 mm, elliptic to ovoid.
Recognition
Distinguished from T. inconspicua subsp. brevistyla by the carpels with obvious multiseptate stigmatic hairs to 1 mm long compared with a capitate head with much reduced stigmatic hairs and fruits elliptic to ovoid in shape rather than elliptic to globose.
Distribution
North Island: Northland – In dune lakes behind coastal dunes of the west coast between 34.9° and 36.5° latitude (Lakes Ngatu, Rotoroa, Waikare, Taharoa, Kai Iwi, Rotokawau).
Habitat
In dune lakes to a depth of about 1 m (occasionally exposed above the water in a dry season, Edgar 1970); 20–70 m a.s.l. Growing in sand and silt, occasionally in peaty sediment, often part of the aquatic turf community and sometimes amongst taller sedges in the shallows.
Biostatus
Indigenous (Endemic)
Nationally Critical B (3/1). Reported to have declined since 1998, with lake-wide extinction in seven of the thirteen lakes reported to have supported populations (Smissen et al. 2019).
Phenology
Flowering Oct.–Jan.; Fruiting from Jan. onwards.
Cytology
2n = c. 24 (de Lange et al. 2004; AK 253948).
Images
Bibliography
Cheeseman, T.F. 1906: Manual of the New Zealand Flora. Government Printer, Wellington.
Cheeseman, T.F. 1907: Notice of the occurrence of Hydatella, a genus new to the New Zealand flora. Transactions and Proceedings of the Royal Society of New Zealand 39: 433–434.
de Lange, P.J.; Murray, B.G.; Datson, P.M. 2004: Contributions to a chromosome atlas of the New Zealand flora – 38. Counts for 50 families. New Zealand Journal of Botany 42: 873–904.
de Lange, P.J.; Rolfe, J.R.; Barkla J.W.; Courtney, S.P.; Champion, P.D.; Perrie, L.R.; Beadel, S.N.; Ford, K.A.; Breitwieser, I.; Schönberger, I.; Hindmarsh-Walls, R.; Heenan, P.B.; Ladley, K. 2018: Conservation status of New Zealand indigenous vascular plants, 2017. New Zealand Threat Classification Series. No. 22. [Nationally Critical]
de Lange, P.J.; Rolfe, J.R.; Champion, P.D.; Courtney, S.P.; Heenan, P.B.; Barkla, J.W.; Cameron, E.K.; Norton, D.A.; Hitchmough, R.A. 2013: Conservation status of New Zealand indigenous vascular plants, 2012. New Zealand Threat Classification Series 3. Department of Conservation, Wellington. [Nationally Endangered]
Edgar, E. 1970: 12. Centrolepidaceae. In: Moore, L.B.; Edgar, E. Flora of New Zealand. Vol. II. Indigenous Tracheophyta: Monocotyledones except Gramineae. Botany Division DSIR, Wellington. 79–85.
Ford, K.A.; Champion, P.D. 2019: Nymphaeales. In: Breitwieser, I.; Wilton, A.D. (ed.) Flora of New Zealand - Seed Plants. Fascicle 5. Manaaki Whenua Press, Lincoln.
Smissen, R.D.; Ford, K.A.; Champion, P.D.; Heenan, P.B. 2019: Genetic variation in Trithuria inconspicua and T. filamentosa (Hydatellaceae): a new subspecies and a hypothesis of apomixis arising within a predominantly selfing lineage. Australian Systematic Botany 32: 1–11.
Sokoloff, D.D.; Remizowa, M.V.; Macfarlane, T.D.; Rudall, P.J. 2008: Classification of the early-divergent angiosperm family Hydatellaceae: one genus instead of two, four new species and sexual dimorphism in dioecious taxa. Taxon 57(1): 179–200.
