Trithuria inconspicua subsp. brevistyla is a subspecies of Trithuria inconspicua in the family Hydatellaceae endemic to the South Island of New Zealand.
Description Vegetative characteristics It is a 10–40 mm tall,de Lange, P.J. (2024): Trithuria brevistyla Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/trithuria-brevistyla/ (2024-11-13) aquatic, perennial, rhizomatous herb with adventitious roots as well as 8–37 mm long, and 0.4–0.6 mm wide leaves.
Generative characteristics Only female plants are known. Male reproductive structures have not been observed. The 1–5, unisexual, female reproductive units ("flowers") consist of glabrous, terete, 1–6 mm long, and 0.3–0.4 mm wide stalks, which do not elongate with maturity, 2–4(–7) ovate, 1.6–4.0 mm long involucral bracts, and 9–25 carpels with short stigmatic hairs. The globose to ovoid fruit is 0.39–0.56 mm long, and 0.3–0.5 mm wide. It is an apomictic species. Flowering occurs from January to February and fruiting occurs from March to May.
Differentiation from Trithuria inconspicua subsp. inconspicua It differs from the autonymous subspecies Trithuria inconspicua subsp. inconspicua in respect to the morphology of the reproductive structures (stalks not elongating with maturity, short stigmatic hairs, and globose to ovoid fruitsManaaki Whenua – Landcare Research. (n.d.-a). Trithuria inconspicua Cheeseman subsp. inconspicua. Flora of New Zealand. Retrieved November 13, 2024, from https://www.nzflora.info/factsheet/taxon/Trithuria-inconspicua-subsp-inconspicua.html). In addition, male reproductive structures are known from Trithuria inconspicua subsp. inconspicua, whereas Trithuria inconspicua subsp. brevistyla is considered to be female only.
Distribution It is endemic to South Island, New Zealand.
Taxonomy It was published by Kerry Alison Ford in 2019.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), 1-11. The type specimen was collected by K.A.Ford and R.D.Smissen in Mary Bay, Lake Hauroko, Southland, New Zealand on the 12th of March 2015.Trithuria inconspicua subsp. brevistyla | International Plant Names Index. (n.d.). Retrieved November 13, 2024, from https://www.ipni.org/n/77200751-1 Trithuria inconspicua is placed in Trithuria sect. Hydatella.Iles, W. J., Rudall, P. J., Sokoloff, D. D., Remizowa, M. V., Macfarlane, T. D., Logacheva, M. D., & Graham, S. W. (2012). Molecular phylogenetics of Hydatellaceae (Nymphaeales): Sexual‐system homoplasy and a new sectional classification. American Journal of Botany, 99(4), 663-676. It was elevated to the status of the separate species Trithuria brevistyla (K.A.Ford) de Lange & Mosyakin by Peter James de Lange and Sergei Leonidovich Mosyakin within the same year of the original publication (2019),de LANGE, P. J., & Mosyakin, S. L. (2019). Trithuria brevistyla (Hydatellaceae), a new combination for the New Zealand endemic species from the South Island. Ukrainian Botanical Journal, 76(2), 95-100. yet there appears to be no consensus for this decision. Trithuria brevistyla (K.A.Ford) de Lange & Mosyakin is treated as a synonym of Trithuria inconspicua subsp. brevistyla K.A.Ford by several sources,Trithuria inconspicua subsp. brevistyla K.A.Ford. (n.d.). WFO Plant List | World Flora Online. Retrieved November 13, 2024, from https://wfoplantlist.org/taxon/wfo-0001368143-2024-06?page=1 but others accept the designation as a separate species.
Etymology The subspecific epithet brevistyla, from the Latin brevis meaning "brief", and stylus meaning "pencil", refers to the short stigmatic hairs found in this subspecies.Manaaki Whenua – Landcare Research. (n.d.-b). Trithuria inconspicua subsp. brevistyla K.A.Ford. Flora of New Zealand. Retrieved November 13, 2024, from https://www.nzflora.info/factsheet/taxon/Trithuria-inconspicua-subsp-brevistyla.htmlManaaki Whenua – Landcare Research. (n.d.). Trithuria inconspicua subsp. brevistyla K.A.Ford. Biota of New Zealand. Retrieved November 13, 2024, from https://biotanz.landcareresearch.co.nz/scientific-names/a1a1acd8-9b4f-4a14-a384-967383749bbe
Conservation It is classified as Nationally Endangered (E).Johnson, P. N., Lee, W. G., & Khan, S. (2022). Wetlands of the Otago Region. The total area of its habitat is ≤ 100 ha (1 km2).de Lange, P. J., Gosden, J., Courtney, S. P., Fergus, A. J., Barkla, J. W., Beadel, S. M., ... & Michel, P. (2024). Conservation status of vascular plants in Aotearoa New Zealand, 2023. New Zealand Threat Classification Series, 43.
Ecology It occurs in lakes at depths of 0.3–2 m, where it grows in gravel, silt, and sand substrates. Rarely during dry seasons it becomes exposed above the water level.
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