Alismatales

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Alismatales
AlismaPlant1.jpg
Alisma plantago-aquatica
Scientific classification e
Kingdom: Plantae
Clade: Angiosperms
Clade: Monocots
Order: Alismatales
R.Br. ex Bercht. & J.Presl[1]
Families

See Classification

Snake lily (Dracunculus vulgaris) of Araceae family in Crete, Greece.

Alismatales (alismatids) is an order of flowering plants including about 4500 species. Plants assigned to this order are mostly tropical or aquatic. Some grow in fresh water, some in marine habitats.

Description[edit]

Alismatales comprise herbaceous flowering plants of aquatic and marshy habitats, and the only monocots known to have green embryos other than the Amaryllidaceae. They also include the only marine angiosperms.[2] The flowers are usually arranged in inflorescences, and the mature seeds lack endosperm.

Both marine and freshwater forms include those with staminate flowers that detach from the parent plant and float to the surface where they become pollinated. In others, pollination occurs underwater where pollen may form elongated strands, increasing chance of success. Most aquatic species have a totally submerged juvenile phase, and flowers are either floating or emergent. Vegetation may be totally submersed, have floating leaves, or protrude from the water. Collectively they are commonly known as "water plantain".[3]

Taxonomy[edit]

Alismatales contains about 165 genera in 13 families, with a cosmopolitan distribution. Phylogenetically it is a basal monocot, diverging early in evolution relative to the lilioid and commenelid monocot lineages.[4] Together with the Acorales, Alismatales are referred to informally as the alismatid monocots.[5]

Early systems[edit]

The Cronquist system (1981) places the Alismatales in subclass Alismatidae, class Liliopsida [= monocotyledons] and includes only three families as shown:

Cronquist's subclass Alismatidae conformed fairly closely to the order Alismatales as defined by APG, minus the Araceae.

The Dahlgren system places the Alismatales in the superorder Alismatanae in the subclass Liliidae [= monocotyledons] in the class Magnoliopsida [= angiosperms] with the following families included:

In Tahktajan's classification (1997), the Order Alismatales contains only the Alismataceae and Limnocharitaceae making it equivalent to the Alismataceae as revised in APG-III. Other families included in the Alismatates as currently defined are here distributed among ten additional orders, all of which are assigned, with the following exception, to the Subclass Alismatidae. Araceae in Tahktajan 1997 is assigned to the Arales and placed in the Subclass Aridae; Tofieldiaceae to the Melanthiales and placed in the Liliidae.[6]

Angiosperm Phylogeny Group[edit]

The Angiosperm Phylogeny Group system (APG) of 1998 and APG II (2003) assigned the Alismatales to the monocots, which may be thought of as an unranked clade containing the families listed below. The biggest departure from earlier systems (see below) is the inclusion of family Araceae. By its inclusion the order has grown enormously in number of species. The family Araceae alone accounts for about a hundred genera, totaling over two thousand species. The rest of the families together contain only about five hundred species, many of which are in very small families.[7]

The APG III system (2009) differs only in that the Limnocharitaceae are combined with the Alismataceae; it was also suggested that the genus Maundia (of the Juncaginaceae) could be separated into a monogeneric family, Maundiaceae, but the authors noted that more study was necessary before Maundiaceae could be recognized.[1]

In APG IV (2016), it was decided that there was sufficient evidence to elevate Maundia to family level as the monogeneric Maundiaceae.[7] The authors considered including a number of the smaller orders within Juncaginaceae, but an online survey of botanists and other users found little support for this "lumping" approach.[8] Consequently the family structure for AP IV is:

Phylogeny[edit]

Cladogram showing the orders of monocots (Lilianae sensu Chase & Reveal)[9] based on molecular phylogenetic evidence.

Lilianae sensu Chase & Reveal[9]



 Acorales 




 Alismatales 




 Petrosaviales 





 Dioscoreales 



 Pandanales 





 Liliales 




 Asparagales 


commelinids

 Dasypogonaceae



 Arecales



 Poales




 Zingiberales



 Commelinales












Alismatid monocots

References[edit]

Bibliography[edit]

External links[edit]