''Trithuria'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of small ephemeral aquatic

herb Herbs are a widely distributed and widespread group of plants, excluding vegetables, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal purposes, or for fragrances. Culinary use typically distingu ...

that represent the only members of the family

Hydatellaceae ''Trithuria'' is a genus of small ephemeral aquatic herb that represent the only members of the family Hydatellaceae found in India, Australia, and New Zealand. Almost all described species of ''Trithuria'' are found in Australia, with the exce ...

found in

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

, and

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

.Kew World Checklist of Selected Plant Families
/ref> Almost all described species of ''Trithuria'' are found in Australia, with the exception of ''T. inconspicua'' and ''T. konkanensis'', from New Zealand and India respectively.Dmitry D. Sokoloff, Margarita V. Remizowa, Terry D. Macfarlane, and Paula J. Rudall. 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.Yadav SR, Janarthanam MK. 1995 Trithuria konkanensis (Hydatellaceae), eine neue Art aus Indien. ''Aqua Planta'' 20. (3): 91-97 (1995). Until DNA sequence data and a reinterpretation of morphology proved otherwise, these plants were believed to be monocots related to the grasses (Poaceae). They are unique in being the only plants besides two members of

Triuridaceae Triuridaceae are a family of tropical and subtropical flowering plants, including nine genera with a total of approximately 55 known species. All members lack chlorophyll and are mycoheterotrophic (obtain food by digesting intracellular fungi, o ...

(''Lacandonia schizmatica'' and ''L. braziliana'') in which the stamens are centred and surrounded by the pistils; in Hydatellaceae the resulting 'flowers' may instead represent condensed inflorescences or non-flowers. These diminutive, superficially moss-like, aquatic plants are the closest living relatives of a clade comprising two closely related water-lily families

Nymphaeaceae Nymphaeaceae () is a family of flowering plants, commonly called water lilies. They live as rhizomatous aquatic herbs in temperate climate, temperate and tropical climates around the world. The family contains five genera with about 70 know ...

and Cabombaceae. Together, these three families compose the

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Nymphaeales The Nymphaeales are an order of flowering plants, consisting of three families of aquatic plants, the Hydatellaceae, the Cabombaceae, and the Nymphaeaceae (water lilies). It is one of the three orders of basal angiosperms, an early-divergin ...

in the

APG III system The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy being developed by the Angiosperm Phylogeny Group (APG). Published in 2009, it was superseded in 2016 by a f ...

of flowering plant classification. ''Trithuria'' (Hydatellaceae) diverged from the rest of Nymphaeales soon after Nymphaeales diverged from its

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

, although the crown clade evolved relatively recently, in the early Miocene (~19 Ma;). The order as a whole is the sister group of all flowering plants except

Amborellales ''Amborella'' is a monotypic genus of understory shrubs or small trees endemic to the main island, Grande Terre, of New Caledonia in the southwest Pacific Ocean. The genus is the only member of the family Amborellaceae and the order Amborella ...

. ''Trithuria'' exhibits a remarkable similarity to '' Centrolepis'' and species of both genera were mistaken for members of the other genus.Sokoloff, D. D., Remizowa, M. V., Linder, H. P., & Rudall, P. J. (2009)
"Morphology and development of the gynoecium in Centrolepidaceae: the most remarkable range of variation in Poales."
American Journal of Botany, 96(11), 1925-1940. The genus consists of tiny, relatively simple plants occurring in Australasia and India. It was formerly considered to be related to the grasses and sedges (order

Poales The Poales are a large order (biology), order of flowering plants in the monocotyledons, and includes families of plants such as the Poaceae, grasses, bromeliads, Juncaceae, rushes and Cyperaceae, sedges. 14 plant families are currently recogniz ...

), but has been reassigned to the order

as a result of DNA and morphological analyses showing that it represents one of the earliest groups to split off in flowering-plant phylogeny, rather than having a close relationship to

monocots Monocotyledons (), commonly referred to as monocots, ( Lilianae '' sensu'' Chase & Reveal) are flowering plants whose seeds contain only one embryonic leaf, or cotyledon. A monocot taxon has been in use for several decades, but with various ranks a ...

, which it bears a superficial resemblance to due to

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...

Description

Plants are submerged and emergent aquatic plants, rooted in the substrate below the water. They are tiny plants, just a few cm tall. Most species are ephemeral aquatics that flower in vernal pools when the water draws down, but several species are submerged perennials found in shallow lakes. The simple leaves are concentrated basally around a short stem. Individual species are cosexual (with several types of hermaphroditic conditions) or

dioecious Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is ...

, and are either

wind-pollinated Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Almost all gymnosperms are anemophilous, as are many plants in the order Poales, including Poaceae, grasses, Cyperaceae, sedges, and Juncaceae, rushes. ...

(anemophilous) or self-pollinating ( autogamous). Two predominantly

apomictic In botany, apomixis is asexual reproduction, asexual development of seed or embryo without Fertilisation, fertilization. However, other definitions include replacement of the seed by a plantlet or replacement of the flower by bulbils. Apomictic ...

species are also known. Flower-like reproductive units are composed of small collections of minute stamen- and/or pistil-like structures that may each represent very reduced individual flower, so that the reproductive units may be pseudanthia. The non-fleshy fruits are follicles or

achene An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple fruit, simple dry fruits, dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and Dehi ...

Cytology

The diploid chromosome count of ''Trithuria inconspicua'' subsp. ''inconspicua'' is 2n = c. 24. The diploid chromosome count of ''Trithuria submersa'' is 2n = 56.Flora of New Zealand , Taxon Profile , ''Trithuria''. (n.d.). Retrieved July 26, 2023, from https://www.nzflora.info/factsheet/taxon/Trithuria.html The diploid chromosome count of the tetraploid species ''Trithuria konkanensis'' 2n = 40.Remizowa, M. V., Sokoloff, D. D., Macfarlane, T. D., Yadav, S. R., Prychid, C. J., & Rudall, P. J. (2008)
"Comparative pollen morphology in the early‐divergent angiosperm family Hydatellaceae reveals variation at the infraspecific level."
Grana, 47(2), 81-100. The diploid chromosome count of ''Trithuria australis'' is 2n = 14.Sokoloff, D. D., Marques, I., Macfarlane, T. D., Remizowa, M. V., Lam, V. K. Y., Pellicer, J., … Graham, S. W. (2019). Cryptic species in an ancient flowering-plant lineage (Hydatellaceae, Nymphaeales) revealed by molecular and micromorphological data. TAXON, 68(1), 1–19. doi:10.1002/tax.12026

Taxonomy

The genus ''Trithuria'' was described by Joseph Dalton Hooker in 1858 with the type species ''Trithuria submersa'' It has two synonyms: In 1888 the genus ''Juncella'' was described without a type designation''Juncella'' F.Muell. ex Hieron. (n.d.). The Australian National Species List (auNSL). Retrieved November 17, 2024, from https://biodiversity.org.au/nsl/services/rest/instance/apni/520743 by Georg Hans Emmo Wolfgang Hieronymus based on previous work by

Ferdinand von Mueller Baron Sir Ferdinand Jacob Heinrich von Mueller, (; 30 June 1825 – 10 October 1896) was a German-Australian physician, geographer, and most notably, a botanist. He was appointed government botanist for the then colony of Victoria, Australia ...

. Mueller had invalidly published the nomen invalidum and

nomen nudum In Taxonomy (biology), taxonomy, a ''nomen nudum'' ('naked name'; plural ''nomina nuda'') is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be one, but it has not been published ...

''Juncella tasmanica'' in 1854. ''Juncella'' is a

nomen illegitimum ''Nomen illegitimum'' (Latin for illegitimate name) is a technical term used mainly in botany. It is usually abbreviated as ''nom. illeg.'' Although the International Code of Nomenclature for algae, fungi, and plants uses Latin terms as qualif ...

. In 1904 the genus ''Hydatella'' was described by Friedrich Ludwig Emil DielsHamann, U. (1976)
Hydatellaceae—a new family of Monocotyledoneae.
New Zealand Journal of Botany, 14(2), 193-196. without a type designation,''Hydatella'' Diels. (n.d.). The Australian National Species List (auNSL). Retrieved November 17, 2024, from https://biodiversity.org.au/nsl/services/rest/name/apni/86441/api/apni-format but the

lectotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to anchor or centralizes ...

''Hydatella australis'' has been designated in 2008. The genus ''Hydatella'' was synonymised with ''Trithuria'' in 2008. ''Trithuria'' was initially placed in the family Centrolepidaceae (now synonymous with

Restionaceae The Restionaceae, also called restiads and restios, are a family of flowering plants native to the Southern Hemisphere; they vary from a few centimeters to 3 meters in height. Following the APG IV (2016): the family now includes the former famil ...

), which is placed in the order

Linder, H. P., & Rudall, P. J. (2005)
Evolutionary history of Poales.
Annu. Rev. Ecol. Evol. Syst., 36(1), 107-124. but it was separated as its own family Hydatellaceae by Ulrich Hamann in 1976 with ''Hydatella'' as the type genus. Upon its separation, Hamann stated the new families affinity or placement were still obscure. The correct placement of the family became apparent in 2007, when it was identified as a basal angiosperm lineage. The family Hydatellaceae is now placed in the order Nymphaeales .WFO (2024): Nymphaeales Salisb. ex Bercht. & J. Presl. Published on the Internet;http://www.worldfloraonline.org/taxon/wfo-9000000354. Accessed on: 17 Nov 2024 Alternatively, it is placed in a separate order Hydatellales validly published by James Lauritz Reveal and Alexander Borissowitsch Doweld in 1999 based on previous work by

Arthur Cronquist Arthur John Cronquist (March 19, 1919 – March 22, 1992) was an American biologist, botanist and a specialist on Compositae. He is considered one of the most influential botanists of the 20th century, largely due to his formulation of the Cr ...

(see the

Cronquist system The Cronquist system is a list of systems of plant taxonomy, taxonomic classification system of angiosperms, flowering plants. It was developed by Arthur Cronquist in a series of monographs and texts, including ''The Evolution and Classification of ...

).Doweld A.B. 2022
New names of fossil Nymphaeaceae and allied forms.
Geophytology 52(1&2): 1–28.Reveal, J. L., & Doweld, A. B. (1999). Validation of Some Suprageneric Names in Magnoliophyta. Novon, 9(4), 549–553. https://doi.org/10.2307/3392163 This is however not widely accepted, as the order Hydatellales is mostly treated as a synonym of Nymphaeales.Manaaki Whenua – Landcare Research. (n.d.-b). Nymphaeales Salisb. ex Bercht. & J.Presl. Flora of New Zealand Online. Retrieved November 17, 2024, from https://www.nzflora.info/factsheet/taxon/Nymphaeales.htmlReveal, J. L. (2012)
An outline of a classification scheme for extant flowering plants.
Phytoneuron, 37(1), 1-221.Reveal, J. L., & Chase, M. W. (2011)
APG III: Bibliographical information and synonymy of Magnoliidae.
Phytotaxa, 19, 71-134.

Species and distribution

Trithuria has at least 13 species, although species diversity in the family has probably been substantially underestimated. # '' Trithuria austinensis'' D.D.Sokoloff, Remizowa, T.D.Macfarl. & Rudall Western Australia # '' Trithuria australis'' (Diels) D.D.Sokoloff, Remizowa, T.D.Macfarl. & Rudall - Western Australia # '' Trithuria bibracteata'' Stapf ex D.A.Cooke - Western Australia # '' Trithuria cookeana'' D.D.Sokoloff, Remizowa, T.D.Macfarl. & Rudall - Northern Territory of Australia # '' Trithuria cowieana'' D.D.Sokoloff, Remizowa, T.D.Macfarl. & Rudall - Northern Territory # '' Trithuria filamentosa'' Rodway - Tasmania # '' Trithuria fitzgeraldii'' D.D.Sokoloff, I.Marques, T.D.Macfarl., Rudall & S.W.Graham - Western Australia # '' Trithuria inconspicua'' Cheeseman - North Island of New Zealand
''Trithuria'' inconspicua subsp. ''brevistyla'' K.A.Ford - endemic to South Island, New Zealand # '' Trithuria konkanensis'' S.R.Yadav & Janarth. - Maharashtra # '' Trithuria lanterna'' D.A.Cooke - Northern Territory, Western Australia, Queensland # '' Trithuria occidentalis'' Benth. - Western Australia # '' Trithuria polybracteata'' D.A.Cooke ex D.D.Sokoloff, Remizowa, T.D.Macfarl. & Rudall - Western Australia # '' Trithuria submersa'' Hook.f. - Western Australia, South Australia, Victoria, New South Wales, Tasmania

Etymology

The generic name ''Trithuria'' is derived from the Greek words τρεις ''treis'' meaning "three", and θυρις ''thyris'' meaning "window". It references the dehiscence of the capsule fruit.Hooker, Joseph Dalton, Fitch, W. H., & Reeve Brothers. (1844). The botany of the Antarctic voyage of H.M. discovery ships Erebus and Terror in the Years 1839-1843 :under the command of Captain Sir James Clark Ross (Vol. 3, Issue 2, pp. 78-79). Reeve Brothers. https://www.biodiversitylibrary.org/page/28467263Department for Environment and Water. (n.d.). ''Trithuria submersa'' (Hydatellaceae) , Seeds of South Australia - Species information. Retrieved July 26, 2023, from https://spapps.environment.sa.gov.au/SeedsOfSA/speciesinformation.html?rid=4619

Conservation

The

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

conservation status of ''Trithuria lanterna'' is Least Concern (LC).Brummitt, N. 2013. ''Trithuria lanterna''. The IUCN Red List of Threatened Species 2013: e.T44392948A44408157. https://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T44392948A44408157.en. Accessed on 13 December 2024. ''Trithuria inconspicua'' is critically endangered.Critically endangered Northland lake plant voted NZ’s favourite plant 2024. (2024, November 5). Northland Regional Council. Retrieved December 13, 2024, from https://www.nrc.govt.nz/news/2024/november/critically-endangered-northland-lake-plant-voted-nz-s-favourite-plant-2024/

References

External links

:* Hydatellaceae in L. Watson and M.J. Dallwitz (1992 onwards).,
The families of flowering plants
descriptions, illustrations, identification, information retrieval.'' Version: 27 April 2006. https://web.archive.org/web/20060424062016/http://delta-intkey.com/ :
Hydatellaceae photographs
:
NCBI Taxonomy Browser
{{Angiosperm families Nymphaeales genera Aquatic plants Nymphaeales