Dispersal and Paleoecology of Tropical Podocarps

Abstract

The paleoecology of tropical Podocarpaceae is reviewed for Africa and Southeast Asia. The family first appeared in the Triassic of Gondwana, after which it diversified through the Cretaceous and earliest Tertiary, and although some Northern Hemisphere Jurassic records are known, it has essentially remained a southern or southern-derived family until the present day. It seems to show a preference for areas of wet climate throughout its history. Podocarpus sensu lato dispersed into Southeast Asia during the late Eocene, and its present distribution is best explained by dispersal from India and possibly multiple long-distance dispersal events from Australia. Dacrydium reached Southeast Asia during the early Oligocene, presumably by island hopping, via the Ninety East Ridge and India and subsequently expanded its range to Japan during the middle Miocene climatic optimum. It is likely that the dispersal pathway was via low-altitude heath forests. Dacrycarpus and Phyllocladus dispersed into New Guinea as the island became established during the late Miocene and then island hopped to Borneo during the mid-Pliocene. Dacrycarpus subsequently reached Sumatra and the Malay Peninsula during the Pleistocene. In Africa, Podocarpus sensu lato was probably present in upland areas during the mid-Tertiary but dispersed by island hopping between montane areas to West Africa in the late Pliocene. In both Africa and Southeast Asia, the Podocarpaceae have clearly increased their range within the low latitudes following mid-Pliocene global climate deterioration and the Northern Hemisphere ice expansion.