HISTORICAL BIOGEOGRAPHY OF THE PREDOMINANTLY NEOTROPICAL SUBFAMILY CINCHONOIDEAE (RUBIACEAE): INTO OR OUT OF AMERICA?

The Rubiaceae is the fifth largest plant family and is found on all continents, mostly in (sub-)tropical regions. Despite a large representation of Rubiaceae in the Paleotropics, the subfamily Cinchonoideae has its primary distribution in the Neotropics. Within the Cinchonoideae only two tribes, Naucleeae and Hymenodictyeae, have Paleotropical centers of distribution. In this study, we used information from five chloroplast DNA markers and fossil data to investigate when the subfamily was established in the Neotropics as well as major subsequent dispersal events within and out of the Neotropics and within the Paleotropics. Our results show that the ancestor of Cinchonoideae and its sister, Ixoroideae, was present in South America during the Late Cretaceous. Dispersal to Central America was estimated to occur during the Early Paleocene, and subsequent dispersals to the Caribbean islands occurred during the Oligocene-Miocene. The ancestor of Naucleeae and Hymenodictyeae dispersed to the Paleotropics no later than the Eocene, and the findings of fossils of Cephalanthus in Europe and western Siberia support its presence in the boreotropical forests. Long-distance, trans-Pacific dispersal during the Miocene was indicated for the remaining Paleotropical Cinchonoideae.