Poaceae , also known as the True Grasses, is the fourth largest plant family in the world with around 12,000 species and roughly 800 genera. [1] [2] They contain, among others, the cereal crop species and other plants of economic importance, such as the bamboos, and several important weeds.
Grasses probably originated in the understory of tropical rainforests in the Late Cretaceous, but have since come to occupy a wide range of different habitats. [3] [4] Notably, they are the dominant species in grasslands, open habitats that cover around one fifth of the earth's terrestrial surface. [3] The C4 photosynthetic pathway has evolved at least 22 times independently in the grasses; C4 species are more competitive than C3 plants in open habitats with high light intensity and warm temperatures. [5]
The deeper relationships in the family have been resolved by recent molecular phylogenetic work. [5] This has been translated into a modern classification which divides the grasses into twelve subfamilies and a number of tribes, with large tribes further divided into subtribes. [1]
Anomochlooideae, Pharoideae and Puelioideae are early diverging lineages containing only a few species. Most of the diversity falls into the two big BOP and PACMAD clades, which each contain roughly half of the family's species. C4 lineages have only evolved in the PACMAD clade, whereas many lineages in the BOP clade have evolved adaptations to cold climate.
While the higher-level classification of the grasses is now relatively well understood, taxonomic efforts continue at the species and genera level, and with continuing phylogenetic research, a number of names is likely to change. [6] The list of genera below is therefore likely to evolve with further study.
793 genera are currently accepted: [7]
Calamagrostis is a genus of flowering plants in the grass family Poaceae, with about 260 species that occur mainly in temperate regions of the globe. Towards equatorial latitudes, species of Calamagrostis generally occur at higher elevations. These tufted perennials usually have hairless narrow leaves. The ligules are usually blunt. The inflorescence forms a panicle. Some may be reed-like.
Cenchrus is a widespread genus of plants in the grass family. Its species are native to many countries in Asia, Africa, Australia, the Americas, and various oceanic islands.
Deschampsia is a genus of plants in the grass family, commonly known as hair grass or tussock grass. The genus is widespread across many countries.
Muhlenbergia is a genus of plants in the grass family.
Setaria is a widespread genus of plants in the grass family. The name is derived from the Latin word seta, meaning "bristle" or "hair", which refers to the bristly spikelets.
Polypogon is a nearly cosmopolitan genus of plants in the grass family, commonly known beard grass or rabbitsfoot grass.
Axonopus is a genus of plants in the grass family, known generally as carpet grass. They are native primarily to the tropical and subtropical regions of the Americas with one species in tropical Africa and another on Easter Island. They are sometimes rhizomatous and many are tolerant of periodic submersion.
Urochloa is a genus of plants in the grass family, native to Eurasia, Africa, Australia, Mexico, and the Pacific Islands. Common names include signalgrass.
Leptochloa is a widespread genus of Asian, African, Australian, and American plants in the grass family.