AN OVERVIEW OF THE PHYLOGENETIC RELATIONSHIPS OF BROMUS PUMILIO (POACEAE) AND ALLIES BASED ON nrDNA ITS AND trnL-F SEQUENCES

According to various taxonomic treatments, Bromus has been divided into 8 to 9 sections, subgenera or even separate genera. The relationship of Bromus pumilio (syn.: Boissiera squarrosa) with other species of Bromus has long been a matter of dispute. To clarify this problem, the nuclear ribosomal DNA ITS and chloroplast DNA trnL-F sequences for 31 and 28 species respectively were used to reconstruct the phylogenetic relationship and reveal the infrageneric boundaries. Molecular analysis performed by Maximum Parsimony analyses and Bayesian method. The results based on nrDNA ITS show that sects. Bromus, Ceratochloa, Genea, Mexibromus and Neobromus are monophyletic, while the plastid data doesn’t support the monophyly of any sections in the genus Bromus.Evidence based on the nrDNA ITS data doesn’t show any close relationships between B. pumilio (sect. Boissiera) and B. danthoniae or B. lanceolatus (sect. Bromus) and instead robustly supports B. pumilio as the sister group of B. gracillimus (sect. Nevskiella), while in the plastid data B. pumilio is the sister group of a clade comprising B. inermis (sect. Pnigma), B. gunckelii (sect. Neobromus)and species of sect. Ceratochloa.