We present here a molecular phylogenetic study of Plantago L.(Plantaginaceae) that analysed nucleotide variation in the internal transcribed spacers (ITS) of nuclear ribosomal and plastid trnL-F regions. We include 57 Plantago species and two Aragoa species as the ingroup and three Veronica species as the outgroup. Phylogenetic analysis using maximum parsimony identified five major clades, corresponding to the taxonomic groups Plantago subgenera Plantago, Coronopus, Psyllium, Littorella and Bougueria. Aragoa is sister to genus Plantago.Plantago subgenus Littorella is sister to the other subgenera of Plantago. The results are in general correlated with a morphological phylogenetic study and iridoid glucoside patterns, but Plantago subgenus Albicans is paraphyletic and should be included in Plantagosubgenus Psyllium sensu lato to obtain a monophyletic clade with six sections. Plantago section Hymenopsyllium is more closely related to section Gnaphaloides than to section Albicans. Plantago subgenus Bougueria is sister to subgenus Psyllium s.l..Section Coronopus in Plantago subgenus Coronopus is subdivided in two series. Only some of the sections can be resolved into series. DNA variation within genus Plantago is high, a result that would not have been predicted on the basis of morphology, which is relatively stereotyped. If we calibrate a molecular clock based on the divergence of P. stauntoni, endemic to New Amsterdam in the Southern Indian Ocean, we calculate the age of the split between Plantago and Aragoa to be 7.1 million years ago, which is congruent with the fossil record.

Additional keywords: Aragoa, Bougueria, iridoid glucosides, Littorella, molecular systematics, Veronicaceae.