Palaeotropical intercontinental disjunctions revisited using a dated phylogenetic hypothesis with nearly complete species level sampling of Ficus subsect. Urostigma (Moraceae)

Aim: Using a dated phylogenetic hypothesis with nearly complete species-level sampling of Ficus subsect. Urostigma with several samples per species, spatiotemporal diversification patterns are clarified, and alternative hypotheses for repeated Palaeotropical intercontinental disjunctions (PIDs) are revisited. Location: (Sub) tropics of Africa, Madagascar, Asia and Australia. Methods: Estimates of divergence times were obtained using a Bayesian relaxed clock analysis via the program BEAST with three calibration points. The output was used to analyse the historical biogeographical patterns via the program RASP (S-DIVA option). The results were compared with existing geological knowledge. Results: The subsection probably originated in Madagascar or Madagascar and India, and dispersed once (or twice) to Africa and once to Asia (1st PID). From Asia the taxa dispersed all over Southeast Asia and finally to the west Pacific. Wallace's Line was relatively recently crossed several times independently by widespread species. One dispersal event back from Asia to Africa is inferred (2nd PID). Main conclusions: The combination of dates and area optimizations for the ancestral nodes of Ficus subsect. Urostigma agree with the tectonic history of the various areas and divergence dates published for Ficus. The first PID is explained by species rafting on India to Asia, after which the majority of species evolved in Asia-Australia. The second PID probably involved dispersal from India via south Asia and Arabia to Africa in the early Miocene before the world-wide climate cooled down and areas became drier. Dispersal over Wallace's Line is by widespread species from which only a few local endemics in east Malesia-Australia developed. The biogeographical history of F. subsect. Urostigma supports a complex picture of several crossings of PIDs and it confirms that the route between Asia and Africa via south Asia and Arabia is often favoured. This route was available during a long period from Oligocene to mid-Miocene and perhaps even up to 2 Ma.