Phylogenetic and biogeographic analyses of the Sino-Himalayan endemic genus Cyananthus (Campanulaceae) and implications for the evolution of its sexual system.

ABSTRACT

Cyananthus (Campanulaceae) is a small genus consisting of ca. 20 species endemic to the Sino-Himalayan region. Based on phylogenetic analysis using nuclear ribosomal ITS and four plastid markers (matK, rbcL, psbA-trnH and trnG-S), our results strongly support the monophyly of Cyananthus and its close relationship with the Codonopsis clade of the platycodonoids. Three major clades are supported, corresponding to the three sections of the genus, with sect. Cyananthus, which mainly occurs in the Himalayas, being a sister to the clade comprising the other two sections (sect. Stenolobi and sect. Annui) distributed primarily in the Hengduan Mountain region. We also observed that Cyananthus exhibits variation in its sexual system, possessing both hermaphroditic and gynodioecious species. Character evolution analyses using Mesquite suggest that gynodioecy evolved from hermaphroditism only once in sect. Stenolobi, but that there is a reversal in C. formosus. Molecular dating and biogeographic analysis with LAGRANGE support dispersal from the Himalayas to the Hengduan Mountains during the early evolution of Cyananthus. The extensive uplift of the Qinghai-Tibetan Plateau and the Hengduan Mountains played an important role in the subsequent diversification of the genus.