Morphological character evolution of Onosma (Boraginaceae) in Iran, based on nuclear and plastid DNA sequences.

Onosma is taxonomically a problematic genus and its infrageneric delimitation is not clear. Using nuclear (ITS) and two plastid (rpl32-trn L and trnH–psbA) markers on 87 species of Onosma throughout their distribution range, phylogenetic relationships within Onosma was reconstructed. Morphological character evolution was mapped on the previously studied nr DNA ITS tree. In the NeighborNet analaysis, the groups formed in the splits graph are correlated to the clades retrieved in the phylogenies. The results suggested that O. rostellata is more closely related to SinoIndian species of Onosma. Among 10 morphological characters selected, six characters including basic chromosome number, type of indumentum, corolla length, nectar trichome, sectioned calyx and calyx cleft represent the most important synapomorphies for Onosma species.