Subordinate Taxa
 Nomenclature
Scientific Name:
Alismataceae Vent., Tabl. Regn. Vég. 2, 157 (1799)
Type Taxon:
 Description

Aquatic (freshwater) emergent or floating-leaved herbs, perennial or annual (rarely), with milky sap; rhizomatous or stoloniferous; vessels absent. Roots adventitious, fibrous. Hermaphrodite, monoecious, polygamomonoecious, or dioecious (rarely). Leaves basal, sheathing, simple, petiolate or sessile, floating, often heterophyllous. Leaf-lamina lobed or non-lobed, margin entire, an apical pore present; venation reticulate, prominent primary veins parallel, secondary veins reticulate. Inflorescence a whorled scape, raceme, panicle, umbel (rarely) or solitary, bracteate, erect or rarely floating. Flowers perfect or imperfect, actinomorphic; perianth hypogynous in two alternate whorls, sepals 3 persistent, petals 3 deciduous. Androecium 0–6–9 to many stamens in 1 or more whorls, free; anthers tetrasporangiate, 2-loculed, basifixed or versatile, extrorse or latrose dehiscence, opening by longitudinal slits; pollination syndrome entomophilous. Gynoecium 0–3–6 to many, ovary superior; carpels free or united at base, in 1 whorl or spiralled, apocarpic or occasionally with two anatropous ovules, or many (Hydrocleys), placentation basal or laminar, styles apical or lateral, persistent; carpel nectariferous region or septal nectaries present. Fruit a single whorl of laterally compressed achenes (forming a ring or cluster), or a follicle. Seeds uncinate-curved, with a horseshoe-shaped embryo, non-endospermic; starch.

 Taxonomy

Alismataceae is part of a group of families known as the alismatids, a large radiation of plants exhibiting numerous adaptations for life in water, both fresh and marine. This treatment follows Les & Tippery (2013) by including Hydrocleys in the Alismataceae, giving a total of about 113 species of herbs in 17 genera. The latter genus was previously placed by Healy & Edgar (1980) in the Butomaceae and by some recent floras in the Limnocharitaceae (Haynes & Holm-Neilsen 1992, Jacobs & McColl 2011).

Based on molecular phylogenies (Les & Cleland 1997, Iles et al. 2013, Ross et al. 2016) the Alismataceae are placed in a well-supported clade known as the ‘petaloid clade’, also including Butomaceae and Hydrocharitaceae; this clade is recognised by Les & Tippery (2013) at the ordinal level as the Alismatales, with its sister clade the ‘tepaloid clade’ named Potamogetonales Dumort. (= Zosterales Nakai).

 Key
1Flowers unisexualSagittaria
1'Flowers bisexual2
2Inflorescence an erect, whorled panicle, corolla pale pink or lilacAlisma
2'Inflorescence a lax scape, appearing solitary on long peduncles, corolla yellowHydrocleys
 Recognition

Plants have milky sap, the flowers are petaloid, and the petals are crumpled in bud and delicate. The seeds are uncinate-curved, with the embryo strongly bent to a horseshoe shape.

 Distribution

Pantropical, temperate; almost cosmopolitan (Haynes & Holm-Neilsen 1992, Haynes & Holm-Neilsen 1994, Wang et al. 2010); 113 species in 17 genera (Les & Tippery 2013).

 Biostatus
Exotic
Number of species in New Zealand within Alismataceae Vent.
CategoryNumber
Exotic: Fully Naturalised6
Total6
 Bibliography
Cronquist, A. 1988: The evolution and classification of flowering plants. The New York Botanic Gardens, New York.
Ford, K.A.; Champion, P.D. 2020: Alismataceae. In: Wilton, A.D. (ed.) Flora of New Zealand - Seed Plants. Fascicle 7. Manaaki Whenua Press, Lincoln.
Haynes, R.R.; Holm-Neilsen, L.B. 1992: The Limnocharitaceae. In: Flora Neotropica. Vol. 56. New York Botanical Garden Press. 1–32.
Haynes, R.R.; Holm-Neilsen, L.B. 1994: The Alismataceae. In: Flora Neotropica. Vol. 64. New York Botanical Garden Press. 1–112.
Iles, W.J.D.; Smith, S.Y.; Graham, S.W. 2013: A well supported phylogenetic framework for the monocot order Alismatales reveals multiple losses of the plastid NADH dehydrogenase complex and a strong long-branch effect. In: Wilkin, P.; Mayo, S.J. (ed.) Early Events in Monocot Evolution. Cambridge University Press, Cambridge, UK. 1–28.
Jacobs, S.W.L.; McColl, K.A. 2011: Limnocharitaceae. In: Wilson, A.J.G. (ed.) Flora of Australia. Vol. 39. ABRS/CSIRO, Melbourne.
Les, D.H.; Cleland, M.A. 1997: Phylogenetic Studies in Alismatidae, II: Evolution of Marine Angiosperms (Seagrasses) and Hydrophily. Systematic Botany 22(3): 443–463.
Les, D.H.; Tippery, N.P. 2013: Evolution of alismatid aquatics. In: Wilkin, P.; Mayo, S.J. (ed.) Early Events in Monocot Evolution. Cambridge University Press, Cambridge, UK.
Mabberley, D.J. 2008: Mabberley's plant book, a portable dictionary of plants, their classification and uses. Edition 3. Cambridge University Press.
Ross, T.G.; Barrett, C.F.; Gomez, M.S.; Lam, V.K.Y.; Henriquez, C.L.; Les, D.H.; Davis, J.I.; Cuenca, A.; Petersen, G.; Seberg, O.; Thadeo, M.; Givnish, T.J.; Conran, J.; Stevenson, D.W.; Graham, S.W. 2016: Plastid phylogenomics and molecular evolution of Alismatales. Cladistics 32: 160–187.
Ventenat, E.P. 1799: Tableau du Règne Végétal, Selon de Méthode de Jussieu. Paris. Vol. 2. J. Drisonnier, Paris.
Wang, Q.; Haynes, R.R.; Hellquist, C.B. 2010: 4. Alismataceae. In: Flora of China (Acoraceae through Cyperaceae). Vol. 23. In: Wu, C.Y.; Raven, P.H.; Hong, D.Y. (ed.) Flora of China. Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis.