Classification and Biogeography of New World Grasses: Anomochlooideae, Pharoideae, Ehrhartoideae, and Bambusoideae

Molecular data support Anomochlooideae and Pharoideae as the two most basal extant clades within Poaceae. Anomochlooideae are endemic to the New World and have two tribes and two genera including the widespread Streptochaeteae (3–4 spp.) and the critically endangered Anomochloeae (1 sp.) of coastal Bahia, Brazil. Pharoideae are pantropical with one tribe, three genera, and 14 species; all eight species of Pharus occur only in the New World. Bambusoideae and Ehrhartoideae are sister groups and together form a clade sister to Pooideae, although support for this set of relationships is low. Ehrhartoideae are a worldwide subfamily represented in the New World by three tribes (Ehrharteae [as several introduced species], Oryzeae, and Streptogyneae), eight genera, and 33 species. Bambusoideae, also worldwide, include two tribes, Bambuseae (woody bamboos) and Olyreae (herbaceous bamboos). The native New World members of Bambuseae (21 genera, 359 spp.) are divided into four subtribes (Arundinariinae, Arthrostylidiinae, Chusqueinae, Guaduinae), including the genera Chusquea (136 spp.), Merostachys (46 spp.), Aulonemia (34 spp.), Arthrostylidium (32 spp.), and Guadua (25 spp.). Together they are most diverse in the central and northern Andes and southeastern Brazil (from Santa Catarina to Bahia), with secondary centers of diversity in tropical Mexico, the West Indies, Costa Rica, and the Guayana Highlands of South America, and all (especially Chusquea) have a number of undescribed species especially in the Andes, Guayana Highlands, and mountainous southeastern Brazil. Olyreae (21 genera, 116–120 spp.) are almost exclusively American and are dominated by Olyra (23 spp.) and Pariana (several to 38 spp.), with one monotypic genus endemic to New Guinea (for which a new subtribe, Buergersiochloinae, is proposed) and with one species (Olyra latifolia) occurring in Africa as well as tropical America.