Smith, James F. , Funke, Mindie M. , Woo, Vincent L. , Garnock-Jones, Philip J. .
A molecular phylogenetic analysis of Coronanthereae (Gesneriaceae) reveals two independent invasions of the Pacific.
THE origin of Pacific plant genera has been a topic of recent interest with a focus on the Hawaiian islands. Gesneriaceae are a family that is widely distributed in the tropics with representatives throughout the Pacific. Coronanthereae are unique among Gesneriaceae with nectaries adnate to ovaries, high chromosome counts, and a distribution bridging Old and New World tropics. The relationship of Coronanthereae to other Gesneriaceae has been difficult due to autapomorphic traits. In this analysis all genera of Coronanthereae and representatives from all other tribes of Gesneriaceae are included. Analyses are based on four chloroplast loci, ITS, and the nuclear low copy gene, GCYC. Duplicate copies of GCYC were found for nearly all Coronanthereae, probably a result of polyploidy. Phylogenetic analyses place Coronanthereae within subfamily Gesnerioideae indicating that the ancestor to Coronanthereae was from the New World tropics and its occurrence in Australia and the South Pacific is the result of two separate dispersal events. Three separate clades are identified within Coronanthereae. One comprises the fleshy-fruited South American genera as well as the Australian Fieldia. A second clade consists of three tree genera, Negria, Depanthus, and Lenbrassia. The third clade consists of Coronanthera and Rhabdothamnus. Estimates applied to the timing of nodes suggest the origin of Coronanthereae and diversification within this tribe are the result of long distance dispersal rather than vicariant events.