Aristidoideae. -- This subfamily has a morphological synapomorphy of a spikelet with one floret and three lemma awns joined basally in a column. It consists of only 3 genera, Aristida L. (315 species), Stipagrostis Nees (55 species) and Sartidia De Winter (4 species) (GrassWorld). All three genera of the subfamily are monophyletic, based on chloroplast and nuclear DNA sequence data (Cerros, Columbus & Barker 2008), but the sections of Henrard are not monophyletic (Henrard 1926-1933, Henrard 1929-1933). Aristida and Stipagrostis both have a C4 NADP-ME photosynthetic pathway, whereas Sartidia is C3. There are 4 centres of diversity for Aristida – North America, Central & South America, Australia and Africa. Geographically, only the Australian species represent a distinct lineage, whereas species from the other 4 areas are present in all the other lineages. In the case of Stipagrostis the Asian species are interspersed between two groups of African species on the cladogram.
Rosa Cerros-Tlatilpa, J. Travis Columbus, and Nigel P. Barker (2011). American J. Bot. 98 (11): 1875, fig.4A.
Rosa Cerros-Tlatilpa, J. Travis Columbus, and Nigel P. Barker (2011). American J. Bot. 98 (11): 1876, fig.4B.