Background and aims: The monophyly of Valerianaceae and the precise delimitation of the family are not totally resolved. Our knowledge on the phylogeny of the group is only partial: on a morphological basis, some contradicting taxonomic proposals have been published, which demonstrates the difficulties in establishing a natural classification of the family and especially in proposing a relevant treatment of the large genus Valeriana. The aims of this study are to contribute to the phylogeny and generic delineation of the Valerianaceae on the basis of molecular data.
Methods: A cladistic analysis of the sequences of one plastid (matK) and one nuclear (ITS) molecular marker was carried out, both individually and in combination.
Key results: The results of the analyses of both regions confirm that the family is monophyletic, with the exclusion of Triplostegia. The tribe Patrinieae is monophyletic, and the tribe Valerianeae is also a natural group. Two of the subtribes of Valerianeae, Fediinae and Centranthinae, are also monophyletic, with the exclusion of the genus Plectritis from Fediinae. The subtribe Valerianinae, on the other hand, is paraphyletic.
Conclusions: Our results confirm, for the first time on a molecular basis, the suggested paraphyly of Valeriana in its present circumscription, with profound nomenclatural and taxonomic implications. The correlation between molecular phylogeny and biogeography is close. In the course of the plastid DNA sequencing, a polymorphism concerning the matK gene was found, a fact that should be carefully evaluated in phylogenetic analyses.