When the Indian subcontinent collided with the Eurasian plate, many animals and plants from Africa and Madagascar dispersed into Asia. The event triggered the biotic diversification of many species — one species of particular interest is the rhacophorid tree frog.

Early studies have suggested that the India–Asia collision occurred during the Paleocene or Early Eocene, around 66–56 million years ago, and many biogeographic studies have relied on this date. Jiatang Li and Yaping Zhang at the Chinese Academy of Sciences in Kunming, China, David Hillis at the University of Texas at Austin, USA and coworkers1 have now tracked the evolutionary path of rhacophorid tree frogs and found data that might move the collision to a more recent date.

The researchers sampled the entire distribution of rhacophorid tree frogs, from tropical Africa and Asia to temperate China and Japan. Their genetic analysis confirmed that rhacophorid tree frogs are close cousins of Madagascan tree frogs. The two clades separated around 59 million years ago, when India collided with Asia. The rhacophorid tree frogs, which migrated to the Indian subcontinent, quickly dispersed throughout Asia.

The researchers also identified multiple dispersal events from Asia back to the Indian subcontinent. This biotic exchange is a demonstration of the mechanisms underlying the rich biodiversity of present-day Southeast Asia. (Edward Duca, Nature China)

(By Su-Qing Liu)