Hydatellaceae

Taxobox
name = Hydatellaceae
regnum = Plantae
divisio = Angiospermae
classis = "see text"
ordo = Nymphaeales
familia = Hydatellaceae
familia_authority = U.Hamann (1976)
subdivision_ranks = Genera
subdivision = "Trithuria"

Hydatellaceae is the botanical name for a family of flowering plants containing the genus "Trithuria", which has been recently re-classified to include the genus "Hydatella"Sokoloff, Dmitry D., Margarita V. Remizowa, Terry D. Macfarlane, 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: 179-200.] . The family consists of about a dozen species. These tiny (few cm tall), relatively simple, aquatic plants are found only in Australasia and India. The simple leaves are concentrated around a short stem basally. The plants are submerged and emergent aquatic annuals, rooted in the substrate below the water.

The members of this plant family are monoecious or dioecious and are likely wind-pollinated (anemophilous), water-pollinated (hydrophilous) or self-pollinating (autogamous). Flower-like reproductive units (which may be pseudanthia) are composed of small collections of minute stamen- and/or pistil-like structures that may each represent very reduced individual flowers. The non-fleshy fruits are follicles or achenes. [T.D. Macfarlane, L. Watson and N.G. Marchant (Editors) (2000 onwards). Western Australian Genera and Families of Flowering Plants. Western Australian Herbarium. Version: August 2002. FloraBase: [http://florabase.calm.wa.gov.au/browse/flora?f=040a&level=f&id=040a Hydatellaceae] . Accessed 20 March 2007.]

Hydatellaceae was for many years assumed to be close relatives of the grasses and sedges and were sometimes included in the family Centrolepidaceae. Even as recently as 2003, the APG II system assigned Hydatellaceae to the grass order Poales in the commelinid monocots. However, research based on DNA and morphology by Saarela "et al." indicates that Hydatellaceae is the living sister group of the water lilies (Nymphaeaceae and Cabombaceae) and thus represents one of the most ancient lineages of flowering plants.Saarela, Jeffery M., Hardeep S. Rai, James A. Doyle, Peter K. Endress, Sarah Mathews, Adam D. Marchant, Barbara G. Briggs & Sean W. Graham. 2007. Hydatellaceae identified as a new branch near the base of the angiosperm phylogenetic tree. "Nature" 446:312-315.]

This realignment indicates that earlier classifications were misleading, a consequence of the apparently reduced vegetative and reproductive morphology of these plants. It also represents the first time in recent history that a plant family has been ejected from the monocots. [Graham, S. [http://www.ubcbotanicalgarden.org/weblog/001995.php A New Understanding of the Early Evolution of Flowering Plants] . University of British Columbia Botanical Garden press release, 14 March 2007.] The APG II system has not yet been formally updated to incorporate the recent findings on Hydatellaceae. However, the Angiosperm Phylogeny Website has now expanded the order Nymphaeales to include Hydatellaceae [Stevens, P. F. (2001 onwards). [http://www.mobot.org/MOBOT/Research/APweb/orders/nymphaealesweb.htm#Nymphaeales Nymphaeales] . Angiosperm Phylogeny Website. Version 7, May 2006. Accessed 21 March 2007.] a classification that is consistent with the findings of Saarela "et al."

References

External links

:* [http://delta-intkey.com/angio/www/Hydatell.htm Hydatellaceae] in L. Watson and M.J. Dallwitz (1992 onwards). " [http://delta-intkey.com/angio/ The families of flowering plants] : descriptions, illustrations, identification, information retrieval." Version: 27th April 2006. http://delta-intkey.com. :* [http://www.ubcbotanicalgarden.org/potd/2007/03/hydatellaceae_1.php Hydatellaceae photographs] :* [http://florabase.calm.wa.gov.au/browse/flora?f=040a&level=g&id=335 "Hydatella" in western Australia] :* [http://florabase.calm.wa.gov.au/browse/flora?f=040a&level=g&id=336 "Trithuria" in western Australia] :* [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=178426&lvl=3&lin=f&keep=1&srchmode=1&unlock NCBI Taxonomy Browser] :* [http://www.csdl.tamu.edu/FLORA/cgi/gateway_family?fam=Hydatellaceae links at CSDL] :* [http://www.rsnz.org/publish/nzjb/1976/24.pdf Original paper recognising the family]