Trithuria occidentalis explained

Trithuria occidentalis is a species of plant in the family Hydatellaceae endemic to Western Australia.^[1]

Description

Vegetative characteristics

It is an annual,^[2] 2-3 cm tall, aquatic herb with 2-3 cm long, and 1 mm wide, red, linear leaves. The midveins of the leaves are prominent.

Generative characteristics

It is a dioecious species with unisexual reproductive units. It exhibits sexual dimorphism in respect to the number of bracts present in the reproductive units ("flowers").^[3] The male reproductive units consist of 3 mm long, erect stalks with 2 lanceolate, 7-8 mm long bracts, as well as 8-10 stamens. The stamens consist of linear, 3 mm long, faintly yellow anthers, and 1 cm long filaments. The female plants produce smaller reproductive units with 8–9(–12) 1.5-2.2mm long bracts enclosing 8-10 carpels. The dehiscent fruit bears seeds, which are sculptured.

Distribution

It is endemic to Western Australia, where it is restricted to a small area north-east from Perth.

Taxonomy

Trithuria occidentalis Benth. was first described by George Bentham in 1878. Later synonyms include Juncella occidentalis (Benth.) Hieron. and Hydatella dioica D.A.Cooke. The type specimen was collected by James Drummond^[4] in Swan River, Western Australia. It is placed in Trithuria sect. Trithuria.^{[5] [6]} The description of Hydatella dioica D.A.Cooke was based on a male individual of Trithuria occidentalis Benth.^[7]

Etymology

The specific epithet occidentalis means western.^{[8] [9]}

Conservation

It is a threatened species.^[10] Under the Western Australian Wildlife Conservation Act of 1950, it is declared as Rare Flora. According to the IUCN criteria, it is classified as Critically Endangered (CR).^[11] It is classified as endangered both under the Environment Protection and Biodiversity Conservation Act 1999 and the Biodiversity Conservation Act 2016.^[12] In 1982, about 1000 plants were recorded. By 2007, the number of recorded individuals had dropped below 200 plants.

Ecology

It occurs in seasonal swamps, and shallow, winter-wet claypans.

Notes and References

1. 163051-1 . Trithuria occidentalis Benth. . 9 November 2024.
2. D.A.Cooke. Hydatella dioica, in (ed.), Flora of Australia. Australian Biological Resources Study, Department of Climate Change, Energy, the Environment and Water: Canberra. https://profiles.ala.org.au/opus/foa/profile/Hydatella%20dioica [Date Accessed: 10 November 2024]
3. 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.
4. Type of Trithuria occidentalis Benth. [family HYDATELLACEAE]. (n.d.). JSTOR. Retrieved November 10, 2024, from https://plants.jstor.org/stable/10.5555/al.ap.specimen.bm000991248
5. Sokoloff, D. D., Remizowa, M. V., Macfarlane, T. D., Conran, J. G., Yadav, S. R., & Rudall, P. J. (2013). Comparative fruit structure in Hydatellaceae (Nymphaeales) reveals specialized pericarp dehiscence in some early–divergent angiosperms with ascidiate carpels. Taxon, 62(1), 40-61.
6. Iles, W. J. D. (2013). The phylogeny and evolution of two ancient lineages of aquatic plants (Doctoral dissertation, University of British Columbia).
7. Rudall, P. (n.d.). Tiny plants make a huge impact. Kew. Retrieved November 10, 2024, from https://www.kew.org/read-and-watch/tiny-plants-make-impact
8. Eggli, U., & Newton, L. E. (2010). Etymological Dictionary of Succulent Plant Names. p. 170. Springer.
9. A Grammatical Dictionary of Botanical Latin. (n.d.-d). Missouri Botanical Garden. Retrieved November 9, 2024, from http://www.mobot.org/mobot/latindict/keyDetail.aspx?keyWord=west
10. Western Australian Herbarium & Department of Biodiversity, Conservation and Attractions. (n.d.). Trithuria occidentalis Benth. Florabase—the Western Australian Flora. Retrieved November 10, 2024, from https://florabase.dbca.wa.gov.au/browse/profile/32658
11. Department of Environment and Conservation (2012) Western Trithuria (Trithuria occidentalis) Interim Recovery Plan 2012–2017. Interim Recovery Plan No. 327. Department of Environment and Conservation, Western Australia.
12. Australian Government & Department of Climate Change, Energy, the Environment and Water. (n.d.). Trithuria occidentalis — Swan Hydatella. Species Profile and Threats Database. Retrieved November 10, 2024, from https://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=42224