Tibet region had role in evolution of mammals

Environmental change when plateau created led to new species appearing, study finds

The tectonic movement that created the Tibetan Plateau – as well as subsequent climate change – have shaped the evolution of Asian mammals over the last 66 million years, a study has found.

The Tibetan Plateau reached an elevation similar to what it is now about 15 million years ago. Since then, major environmental changes and the diverse vegetation along the mountain slopes have triggered the creation of new species, according to the study.

Asia is the birthplace of many extant mammals and is home to 14 out of 36 of the world’s biodiversity hotspots. But previous studies have been limited and a comprehensive understanding of the origin and evolution of mammals in the region has been lacking.

For the study – published in peer-reviewed journal the Proceedings of the National Academy of Sciences on Monday – researchers built more than 2,000 historical biogeographic models comprising over 3,000 species in Asia and adjacent continents to investigate their evolution.

“Asia has desert up north, tropical forests in the south, temperate forests in the east,” Anderson Feijó, the study’s lead author and a researcher with the Chinese Academy of Sciences’ Institute of Zoology in Beijing, was quoted as saying on the website of the Field Museum of Natural History in Chicago, where he was previously a research fellow.

“My idea was to understand how all these regions were connected and how we ended up with different species of mammals in different areas,” Feijó said.

Bruce Patterson, study coauthor and a curator emeritus at the museum, said Asia did not have the most mammal species in the world, but it was a crossroads for connections to other continents. That was why it was critical to study historical mammal exchanges between Asian regions and other continents and to see if those changes could be linked to the region’s geologic and climate events, according to the paper.

The researchers found that the tropical forests of South Asia had served as the main cradle of Asia’s mammal diversity, and that the current high diversity in the region was mainly derived from the original place, or in situ speciation.

Meanwhile, mammal emigration from southern Asia has greatly increased over the past 23 million years, especially towards the Himalayas and the Hengduan Mountains, on the edge of the Tibetan Plateau.

The study found that colonisation – or mammals spreading from southern Asia to the Himalayas and the Hengduan area – had been the dominant mode of species accumulation over time from the two mountainous hotspots.

Compared to southern Asia, the species diversity of other Asian regions is also mainly derived from colonisation events, according to the researchers.