Molecular phylogeny of the genus Pennisetum and Cenchrus (Poaceae)

CHEMISQUY, M. A., DONADIO, S., KELLOGG, E. & MORRONE, O

Ciudad Autónoma Buenos Aires, Argentina

Jornada; VIII Jornadas Multidisciplinarias de la Sociedad Argentina de Biología; 2006

Sociedad Argentina de Biología

The genus Pennisetum (Poaceae: Panicoideae: Paniceae) includes approximately 80 species distributed in tropical and subtropical regions worldwide, having its larger diversity in America and Africa. According to morphological characters, the genus is divided in seven sections: Penicillaria, Brevivalvula, Gymnotrix, Heterostachya, Pennisetum, Dactylophora and Beckeropsis. Cenchrus is close related to Pennisetum, and some species have been placed in both genera. They differ in the bristle shape, while in Pennisetum the bristles are free to the base, in Cenchrus are flattened and united below the base. Both genera belong to a monophyletic group together with Setaria, Ixophorus, Paspalidium, and Stenotaphrum, all characterized by having the inflorescence surrounded by an involucre of bristles ("Bristle clade"). The aims of this work were to analyze the monophyly of Pennisetum, Cenchrus and their relationship wthin the "Bristle clade". The monophyly of the sections of Pennisetum were also tested. The study includes 33 species of Pennisetum, 7 species of Cenchrus, and 7 outgroups. We amplified and sequenced the chloroplast markers ndhF and trnL-F. The sequences were aligned by eye. The matrices were combined and analyzed using maximum parsimony, by the program TNT. The support for the clades was assessed using jackknife and GC analyses. The strict consensus showed that Pennisetum, Cenchrus and Odontelytrum formed a monophyletic group, with high support values. Within this group, neither Pennisetum, nor Cenchrus were monophyletic, since both grouped together in a well-supported clade. Moreover, sections of Pennisetum were not monophyletic and need to be evaluated by a new morphological assessment.