CHENGDU, Oct. 29 (Xinhua) -- A new study has reconstructed the evolutionary history of terrestrial animals on the Qinghai-Xizang Plateau, offering a clearer picture of how the unique fauna of Earth's "Third Pole" took shape over millions of years.
The research, led by a team from the Chengdu Institute of Biology (CIB) under the Chinese Academy of Sciences, was recently published in the journal Proceedings of the National Academy of Sciences (PNAS).
"Overall, the study deepens understanding of how mountain animal life evolves and provides a framework for studying how biodiversity forms in mountain regions worldwide," said Li Jiatang, a researcher at CIB.
Home to many species found nowhere else, the Qinghai-Xizang Plateau is one of the world's biodiversity hotspots, covering about 3.07 million square kilometers and ranging in elevation from 88 to 8,848 meters, according to the researchers.
The plateau platform, the Himalayas and the Hengduan Mountains are the plateau's three major subregions.
Scientists have long been interested in how the plateau's tectonic history and monsoon systems shaped the evolution of local biodiversity. However, earlier studies mostly looked at plants or single animal groups, leaving the overall development of the plateau's land animals poorly understood.
To fill this gap, the researchers combined time-calibrated evolutionary trees covering more than 20,000 species across invertebrates, amphibians, reptiles, birds and mammals. They then reconstructed the evolutionary history of 527 endemic terrestrial animal species on the plateau.
The study found that most of the plateau's endemic land animals did not arrive from elsewhere and then become new species. Instead, many evolved locally, splitting into new species right where they were, something scientists call in situ diversification.
The plateau was also a major receiver of species. The study found that animals moved in nearly twice as often as they moved out. The Qinghai-Xizang Plateau therefore played two roles at once: it was a place where new species formed, and a biogeographic sink that took in more species than it sent out.
The three subregions played very different roles. The Hengduan Mountains were the main source of local species formation, producing many new species. The Himalayas were both a source and a sink, producing new species locally and receiving species from elsewhere. The plateau platform produced very few new species locally, with most of its animal life coming from immigration, making it an important sink and a major receiver of species.
The researchers also examined how geology and climate shaped this evolutionary history. They found that a major climate transition about 34 million years ago marked the onset of sustained species diversification and biological exchange. However, the timing of these processes varied across the three subregions, reflecting differences in their uplift histories and monsoon systems.
The study also found a consistent "plants first, animals later" pattern. By comparing animal evolution with plant studies, the researchers identified this pattern across the plateau and its subregions. Early-colonizing plant groups created suitable ecological niches, laying the foundation for later animal immigration and diversification. ■
