A systematic analysis of Heliotropium, Tournefortia, and allied taxa of the Heliotropiaceae (Boraginales) based on ITS1 sequences and morphological data.

The relationships of Heliotropium, Tournefortia, Schleidenia, Ixorhea, and Ceballosia of the Heliotropiaceae (Boraginaceae in the traditional sense, Boraginales) are investigated using molecular data (ITS1). These genera form a monophyletic group. Five clades can be distinguished on the basis of molecular data, morphological traits, and distribution. In their current circumscription, Tournefortia is polyphyletic and Heliotropium is paraphyletic. Tournefortia section Cyphocyema is the sister group to all other ingroup taxa. Heliotropium section Orthostachys including Schleidenia sensu lato is the well supported sister group of a clade comprising the other species of Heliotropium sensu stricto (s.s.), Tournefortia section Tournefortia, and Ceballosia. Heliotropium s.s. forms two clades: one clade includes all species of the Old World and represents the only monophylum of Heliotropium s.s. The other clade consists of all Heliotropium s.s. species of the New World but also includes Tournefortia section Tournefortia and Ceballosia. The results suggest that taxonomic changes are inevitable.