Eocene out-of-India dispersal of Asian dipterocarps

The Dipterocarpaceae, a well known and economically important family of trees of the tropical rain forests of Asia, comprise over 470 species. These angiosperm trees contribute to 30% of the total area in typical lowland evergreen forests in Southeast Asia. Despite their remarkable diversity and regional ecological dominance, the origins and phytogeographical evolution of the family are poorly understood. The earliest dipterocarp fossils recorded in SE Asia come from Oligocene (34–23 Ma) sediments of Borneo. Here, we report an occurrence of Asian dipterocarps from approximately 53 Ma old sediments from western India based on fossil resin chemistry and palynological data. An important implication of our finding is that Asian dipterocarps must have originated in Gondwana and dispersed from India into Asia once the land connection between the Indian and Asian plate was well established during the middle Eocene (49–41 Ma). Moreover, the present study supports the hypothesis which suggests that many angiosperms did not originate in the SE Asian region, but dispersed into the area from western Gondwanaland.

Research highlights
► Dipterocarpaceae contribute to 30% of the total area in lowland evergreen forests in Southeast Asia.
► The earliest dipterocarp fossils recorded in SE Asia come from Oligocene.
► We report an occurrence of dipterocarps from 53 Ma sediments of western India based on resin chemistry and pollen data.
► Asian dipterocarps were originated in Gondwana and dispersed out-of-India into Asia during the middle Eocene.