The phylogenetic placement of the Old World Gesneriaceae genera Ramonda, Conandron, Bournea, Thamnocharis, and Tengia, all characterized by actinomorphic flowers, has been the subject of much debate. Actinomorphy in Gesneriaceae is rare, with most species exhibiting zygomorphic flowers. The actinomorphic genera have historically been considered “primitive” and lumped in the tribe Ramondeae separate from the remaining Old World Gesneriaceae. In this study, we used nuclear (ITS) and plastid (trnL‐F) DNA for molecular phylogenetic analysis of these five genera along with representative species across the Cyrtandroideae. Our results show that the actinomorphic genera are scattered over several otherwise zygomorphic clades within Cyrtandroideae, and along with previous data, indicate that Ramondeae is an unnatural group. Floral actinomorphy has evolved convergently in different alliances of Old World Gesneriaceae. Ramonda is sister to Haberlea, Bournea is apparently paraphyletic, Conandron seems rather isolated, and Tengia is close to Petrocodon and sister to a group of Chirita sect. Gibbosaccus together with Calcareoboea. We hypothesize that the evolution from zygomorphy to actinomorphy with novel combinations of characters is possibly due to shifts in pollination strategies, such as a switch from nectar‐ to pollen‐rewards.
Origin and phylogenetic relationships of the Old World Gesneriaceae with actinomorphic flowers inferred from ITS and trnL-trnF sequences
Genera: Bournea, Conandron, Ramonda, Tengia, Thamnocharis