Molecular and morphological phylogenetic analysis of Brachiaria and Urochloa (Poaceae)

The taxonomic relationships of Brachiaria and Urochloa have been questioned based on previous morphological studies. In this paper, we reconsider the phylogenetic relationships of these genera using 22 species of Brachiaria and Urochloa and six species of Paniceae as out-groups. The ITS1, 5.8S, and ITS2 region (internal transcribed spacer) of nuclear ribosomal DNA and eight morphological characters of the inflorescence were compiled into a data matrix. The cladistic analyses suggest that Urochloa-Brachiaria as a complex is paraphyletic with Eriochloa and Melinis. Species of all these genera share molecular synapomorphies and belong to the same monophyletic groups. The results confirm the continuous gradation between those genera previously found in several morphological studies. Therefore, the following eight new combinations are made: Urochloa bovonei (Chiov.) A.M. Torres & C.M. Morton, Urochloa dura (Stapf) A.M. Torres & C.M. Morton, Urochloa dura var. dura (Stapf) A.M. Torres & C.M. Morton, Urochloa dura var. pilosa (J.G. Anderson) A.M. Torres & C.M. Morton, Urochloa lachnantha (Hochst.) A.M. Torres & C.M. Morton, Urochloa leersioides (Hochst.) A.M. Torres & C.M. Morton, Urochloa nigropedata (Munro ex Ficalho & Hiern) A.M. Torres & C.M. Morton, and Urochloa subulifolia (Mez) A.M. Torres & C.M. Morton.