Much before the Indian tectonic plate merged with Eurasian one, there was an exchange of species between Indian sub-continent and China and south-east Asia. Land bridges between the two landmasses served as freeways for this exchange of species, says a new study.

Two land bridges connected the two lands around 35 to 40 million years ago, shows the paper from Jesse Grismer, doctoral student at the Biodiversity Institute at the University of Kansas.

"Our paper shows that as India was approaching Eurasia, it was connecting by ephemeral land bridges," Grismer said. "It was these land bridges that allowed for dispersal and exchange of all these species. There were two areas of suitable habitat separated by unsuitable oceans. But once that new area was exposed, species were allowed to disperse into mainland Asia or India, respectively, areas that these species had not been able to previously exploit."

For about 60 million years during the Eocene epoch, the Indian subcontinent was an island which broke off from the ancient continent of Gondwanaland, and drifting toward Eurasia. Even during the drift, the Indian subcontinent saw a blossoming of exceptional wildlife and plants which was exchanged more profusely after contact. While Asian freshwater crabs made their way from India to Asia, dragon lizards moved the other way.

The research appeared in the journal BMC Evolutionary Biology.

"This hypothesis is based on evolutionary relationships between the species used in this study," said Grismer. The study looked at a genomic analysis of Indian Dragon Lizards which revealed multiple origins in Southeast Asia. It merged new genomic data with previous studies and combined the analysis with new geologic studies about Eocene geology.

The Indian Dragon Lizards, or the Draconinae subfamily of the lizard family Agamidae, were an ideal species to study the exchange of biodiversity that took place due to the land bridges, said Grismer, calling for a protection of the species. "They're quite diverse as a group, distributed equally, and so they're great study system for testing a new hypotheses."