Alismataceae are widespread aquatics with diverse floral and vegetative habits but generally are recognizable by their showy flowers, which have petals ranging in color from white to yellow and pink.
Global distribution of Alismataceae
The circumscription of Alismataceae followed here includes three genera (Butomopsis, Hydrocleys, and Limnocharis) included formerly in Limnocharitaceae Takht. Although Limnocharitaceae once were considered to be intermediate phylogenetically between Alismataceae and Butomaceae, contemporary phylogenetic analyses have not supported this disposition. Analysis of rbcL data (Les et al., 1997)  placed Hydrocleys and Limnocharis in a clade with eight core genera of Alismataceae, with neither closely allied to Butomaceae as earlier believed. A more recent combined data analysis that included Butomopsis united all three former Limnocharitaceae genera in a strongly supported clade, which was embedded within Alismataceae (Les & Tippery, 2013). 
Molecular phylogenetic studies of Alismataceae have included analyses incorporating data from 1-17 genes for 2-16 genera (Chen et al., 2012 ; Les & Tippery, 2013).  The overall relationships among the majority of genera have been clarified, with the exception of Albidella and Burnatia, whose precise placements are still unresolved. All genera, however, resolve within one clade, confirming the monophyly of the family.
Intergeneric relationships in Alismataceae (from Les & Tippery, 2013). 
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- In time and with water .. the systematics of alismatid monocotyledons. Early Events in Monocot Evolution (2013).
- Generic phylogeny and historical biogeography of Alismataceae, inferred from multiple DNA sequences. 63, 407 - 416 (2012).