The establishment of Palaeotropical rainforests from Africa to Oceania in relation to plate tectonics and zonal tropical climates

Abstract

Old-world rainforests of the Palaeotropical kingdom became established at different times in different regions with changing opportunities for plant dispersals in relation to Late Cretaceous and Cenozoic plate movements and climate change. The Palaeotropical and Neotropical kingdoms differentiated in the Late Cretaceous. Maastrichtian records of fossil Dipterocarpus pollen from Sudan show that canopy-forming dipterocarp genera evolved in Africa and Dipterocarpoideae and other taxa dispersed to India with the Africa-India floristic interchange. As the Indian Plate drifted towards Asia in the Eocene multiple lineages dispersed to Southeast Asia from about 48 Myr onward, replacing a depauperate flora of East Asian affinity. Tectonic models for Southeast Asia are in conflict, and the different models impact strongly on how to interpret the subsequent evolution of Southeast Asian rainforests. The lowland floras of the islands of Eastern Indonesia and Oceania originated due to dispersals mainly from Southeast Asia and became established after those areas rose above sea level during the Neogene. Palaeotropical rainforests formed in equatorial Africa during the Campanian, India in the late Maastrichtian to Paleocene, Southeast Asia in the middle Eocene and Oceania in the Miocene. The current megadiverse Southeast Asian rainforests are essentially sourced from immigrants.