Trithuria sect. Hydatella is a section within the genus Trithuria native to New Zealand and Australia.de Lange, P., & Mosyakin, S. L. (2019). Trithuria brevistyla (Hydatellaceae), a new combination for the New Zealand endemic species from the South Island.
Description
The apocarpous berry fruit is indehiscent.Romanov, M. S., Bobrov, A. V. C., Iovlev, P. S., Roslov, M. S., Zdravchev, N. S., Sorokin, A. N., ... & Kandidov, M. V. (2024). Fruit and seed structure in the ANA‐grade angiosperms: Ancestral traits and specializations. American Journal of Botany, 111(1), e16264. Pericarp papillae and pericarp ribs are absent. The fruit stalk bears a distal constriction, serving as an abscission zone.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. The seed cuticle is thick.
Taxonomy It was first described as Hydatella by Friedrich Ludwig Emil Diels in 1904.Hydatella Diels. (n.d.). International Plant Names Index. Retrieved June 8, 2025, from https://www.ipni.org/n/6723-1Diels, L., & Pritzel, E. (1905). Fragmenta phytographiae Australiae occidentalis: beiträge zur kenntnis der pflanzen westaustraliens, ihrer lebens-verhältnisse. p. 93. Wilhelm Engelmann. After the former genus Hydatella was merged into Trithuria in 2008,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. the section Trithuria sect. Hydatella was described by Dmitry Dmitrievich Sokoloff, William J. D. Iles, Paula J. Rudall, and Sean W. Graham in 2012.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. Species It has four species:
Trithuria austinensis Trithuria australis Trithuria filamentosa Trithuria inconspicua Trithuria inconspicua subsp. brevistyla
Etymology The section name Hydatella comes from the former genus Hydatella , whose name is derived from the diminutive of ύδωρ (hydor) meaning water.Christenhusz, Maarten J. M., Fay, Michael F. and Chase, Mark W.. "The ANA grade families". Plants of the World: An Illustrated Encyclopedia of Vascular Plants, Chicago: University of Chicago Press, 2017, pp. 88-94. https://doi.org/10.7208/9780226536705-016
Distribution Its species occur in New Zealand (North Island, South Island) and Australia (Tasmania, Australian mainland).
Phylogeny Trithuria sect. Hydatella split from Trithuria sect. Trithuria about 16 million years ago in the Early Miocene.Lin, Q. (2014). Using a low-copy nuclear gene (phosphoglycerate kinase; PGK) to explore the phylogeny of the aquatic plant family Hydatellaceae (Nymphaeales) (Doctoral dissertation, University of British Columbia).
References