The New Zealand Plant Conservation Network

Species

Trithuria brevistyla

Current Conservation Status

2019 - Threatened - Nationally Vulnerable

Conservation status of New Zealand indigenous vascular plants, 2012
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2012 using the New Zealand Threat Classification System (NZTCS). This report includes a statistical summary and brief notes on changes since 2009 and replaces all previous NZTCS lists for vascular plants. Authors: Peter J. de Lange, Jeremy R. Rolfe, Paul D. Champion, Shannel P. Courtney, Peter B. Heenan, John W. Barkla, Ewen K. Cameron, David A. Norton and Rodney A. Hitchmough. File size: 792KB

Authority

Trithuria brevistyla (K.A.Ford) de Lange et Mosyakin

Family

Hydatellaceae

Brief Description

Diminutive, tufted, aquatic herb 10-40 mm tall producing numerous unsheathed fine hair like leaves arranged in fans. Inflorescences inconspicuous, borne on stalks 1–6 mm long. Flowers much reduced. Female only.

Flora Category

Vascular - Native

Structural Class

Dicotyledonous Herbs other than Composites

Synonyms

Trithuria inconspicua subsp. brevistyla K.A.Ford

Distribution

Endemic. New Zealand. South Island reported from Southland at Lakes Poteriteri, Hauroko, Manapouri, Te Anau and South Mavora Lake and from Lake Sylvan, Otago

Habitat

Shallows of lakes (rarely exposed above the water in a dry season), between 35 and 600 m a.s.l. Growing in sand, silt and gravel, sometimes almost completely buried in muddy silt. Often part of the aquatic-turf community, particularly with short-growing shallow water-species in glacial lakes to a depth of ~0.3–2 m.

Features

Aquatic perennial herb, tufted 10–40 mm high, from a shortly branching erect rhizome, trichomes present; copious adventitious roots. Apomictic plants female only. Plants in populations often female only, or plants co-sexual with unisexual or bisexual reproductive units. Leaf-bases weakly dilated (not sheathing), hyaline, toothed auricles present or absent; leaves spreading, glabrous, 8–37 × 0.4–0.6 mm; lamina linear-filiform, adaxially faintly compressed below, terete above, apex rounded with a hydathode. Reproductive units 1–5 per tuft, (3.5–)4–5(–7) mm long, on glabrous terete scapes 1–6 × 0.3–0.4 mm; involucral bracts 2–4(–7), ovate to broad-ovate or narrow-ovate, Female reproductive unit bracts 1.6–4.0 mm long; carpels 9–25, white–pinkish, with stigmatic hairs reduced to a knobbly capitate head (<0.2 mm long). Fruits 0.39–0.56 × 0.3–0.5 mm, ovoid to globose, deciduous from persistent stalks, pericarp thin and membraneous, smooth, indehiscent. Seed faintly reticulate, yellowish-brown to reddish-brown with a darker apical cap (formed by an operculum).

Similar Taxa

Trithuria brevistyla differs from T. inconspicua in the shortened stigmatic hairs forming a knobbly capitate head, the fruit being ovoid to globose (rather than ellipsoid to ovoid), and scapes not elongating with maturity.

Flowering

January - February

Flower Colours

Red / Pink,White

Fruiting

March - May

Propagation Technique

Difficult - should not be removed from the wild.

Threats

Trithuria brevistyla was listed by de Lange et al. (2018), under the tag-name ‘Trithuria aff. inconspicua (CHR 502359; South Island)’, as Threatened–Nationally Vulnerable (with qualifiers data-poor, partial decline). Smissen et al. (2019) suggested that this assessment be elevated to Threatened-Nationally Endangered citing as reasons the low area of occupancy estimated by them at 10 ha and their projected decline of 10–50%. As the New Zealand Threat Lisiting Panel was not consulted over this suggestion as per the requirement of Townsend et al. (2008) the change of status remains a 'suggestion' to be discussed at the next national threat listing in 2023.

Endemic Taxon

Yes

Endemic Genus

No

Endemic Family

No

This page last updated on 9 Jun 2019