Phylogenetic analysis of the Triticeae (Poaceae) based on rpoA sequence data

A phylogenetic analysis was conducted on 31 diploid species representing 21 of the 24 monogenomic genera of the Triticeae. The data used were derived from a 1343- to 1358-bp region of the plastid genome spanning the entire rpoA gene plus minor parts of the petD and rps11 genes and the two intergenic spacers surrounding rpoA. Bromus inermis (Bromeae) was used as an outgroup. A total of 68 variable sites, 25 of them phylogenetically informative, and seven length mutations were detected. The length mutations occurred in the noncoding regions. Phylogenetic analyses were performed on the whole data set and on various subsets. The analysis of the unweighted data resulted in 48 equally parsimonious trees (length 98, CI = 0.88, RI = 0.92, ti = 0.25). A parsimony jackknife analysis proved several clades to be well supported. The effect of transition/transversion weighting was also investigated. In general, congruence with other data sets was negatively effected by weighting. The preferred phylogenetic hypothesis is congruent with a phylogeny based on plastid RFLP data including the same taxa, but it is largely incongruent with phylogenies derived from nuclear rDNA and morphology.