Subclass:
Commelinidae
Links to Family Pages:
Commelinaceae Restionaceae Cyperaceae Sparganiaceae Eriocaulaceae Typhaceae Juncaceae Xyridaceae Poaceae
The subclass Commelinidae consists of 16 families and about 15,000 species. More than 1/2 of all the species belong to the Poaceae (grasses). The grasses and sedges (Cyperaceae) account for about 4/5ths of all species. The Commelinidae has been defined by the absence of septal nectaries, with pollination mediated by pollen gathering bees (e.g., Commelinaceae) or by wind (e.g., Poaceae and Cyperaceae). Floral reduction associated with adaptation to wind pollination is a prevalent trend in the subclass. This reduction series includes the loss of floral parts for wind pollination, the increasing ecological importance of the multi-bracted spikelet (inflorescence), and the development of 1-seeded achene or grain fruits. Vessel elements are generally found in all vegetative organs.
Molecular phylogenetic studies now define the Commelinidae in a broader fashion to include palms (subclass Arecidae in part), a few isolated families of the subclass Liliidae, and the subclass Zingiberidae. This expanded Commelinidae is defined principally on the presence of bound ferulic acid in cell walls. Nectar-mediated pollination is most likely primitive in the subclass with several, independent shifts occurring to both pollen gathering and wind-mediated pollination.
