New World Origins of Southwest Pacific Gesneriaceae: Multiple Movements Across and Within the South Pacific

Coronanthereae is a tribe of ~20 species with a suite of unique morphological characters and a disjunct geographic distribution in the Southern Hemisphere. Three species are found in southern South America and the remainder in the southwest Pacific. It has been suggested, because of this distribution and disjunction, that Coronanthereae represents a relictual Gondwanan group from which the two major lineages in the family, the Old World Cyrtandroideae and the New World Gesnerioideae, originated. We tested this hypothesis by using phylogenetic analyses of nuclear and chloroplast DNA sequences, ancestral-area reconstruction, and molecular dating. The tribe is placed within the mostly Neotropical subfamily Gesnerioideae and comprises three lineages, treated here as subtribes. Two events of dispersal from South America explain the presence of the tribe in the South Pacific. Negriinae, newly recognized here, comprises arborescent genera: Australian Lenbrassia, New Caledonian Depanthus, and Negria from Lord Howe Island. Mitrariinae groups facultatively epiphytic Australian Fieldia with epiphytes from South America, a finding inconsistent with recent placement of Lenbrassia in synonymy of Fieldia. Coronantherinae consists of the arborescent Coronanthera from New Caledonia and the shrub Rhabdothamnus from New Zealand. Ancestral-area reconstruction and molecular dating of the clades support long-distance dispersal mechanisms, rather than Gondwanan vicariance, for explaining geographic distributions