Format: ORAL

Alejandro Quintanar1, Robert J. Soreng2, Paul M. Peterson2, Konstantin Romaschenko2, Carlos Aedo1 , Patricia Barber3

1 Real Jardín Botánico de Madrid CSIC, Madrid, Spain 2 National Museum of Natural History, Smithsonian Institution, Washington DC, USA 3 Department of Africa and Madagascar, Missouri Botanical Garden, St. Louis, USA

Analyses of molecular data accumulated over nearly two decades have revealed extensive polyphyly affecting many of the genera that make up the oats subtribe, Aveninae, a group of subfamily Pooideae grasses of global economic importance. Within Aveninae, Koeleriinae clades A and B (koelerioid grasses) contain most of the biodiversity in the subtribe, including mostly perennial lineages, such as Trisetum s.l. or Koeleria (both worldwide) and other American genera like Sphenopholis and Graphephorum, and a series of annuals like Rostraria and Trisetaria from the Mediterranean (except Limnodea). We present our latest results on the systematic relationships of the koelerioids resulting from the largest sampling of these grasses carried out to date. Our new phylogenetic trees have improved our understanding of the evolution of this diverse group and led to drastic revisions of their classification. Amendments have involved the publication of new genera and the expansion, reduction or resurrection of others. A notable case of reduction is Trisetum, before considered to host ca. 70 perennial species, and now restricted to only three species, one of them annual. In contrast, Koeleria, another large perennial genus from cold or temperate regions of all hemispheres, has grown from 25 to nearly 100 species after absorbing part of the diversity of Trisetum. Aegialina, Acrospelion, and Cinnagrostis were resurrected. The detection of past reticulation events forming Graphephorum and parts of Rostrariasuggest the importance of the hybridization as driving force of evolution in these groups, a common feature with other lineages of supertribe Poodae.