Phylogenetic relationships of Echinolaena and Ichnanthus within Panicoideae (Poaceae) reveal two new genera of tropical grasses.

Echinolaena and Ichnanthus are two tropical grass genera distributed mostly in the Americas, characterized by the presence of rachilla appendages in the shape of convex swellings, scars or wings at the base of the upper anthecium. However, recent studies have shown that rachilla appendages arose several times independently in several groups within Paniceae and Paspaleae (Panicoideae). Thus, this study aimed to assess the monophyly of Echinolaena and Ichnanthus and their relationship to other genera of Paniceae and Paspaleae, especially those including species with rachilla appendages. Parsimony and Bayesian analyses of the cpDNA regions ndhF, rpl16, trnH-(rps19)-psbA, trnL-trnF, trnS-(psbZ)-trnG, and the rDNA ITS region included 29 of the 39 known species of Echinolaena and Ichnanthus, 23 of which were sampled for the first time. The multiple loci analyses indicated that Echinolaena and Ichnanthus are polyphyletic in their current circumscriptions, with species in four distinct lineages within subtribe Paspalinae, each one characterized by a single type of rachilla appendage. Thus, Echinolaena and Ichnanthus are each circumscribed in a narrow sense, and the other two lineages excluded from them are proposed as the new genera Hildaea and Oedochloa, resulting in 15 new combinations and the restablishment of I. oplismenoides Munro ex Döll.