Geological and climatic histories likely shaped the origins of terrestrial vertebrates endemic to the Tibetan Plateau

Aim The Tibetan Plateau (TP) hosts many endemic species, but questions regarding when and from where these species originated have not been comprehensively answered. Here, we provide a synthesis of the biogeographical history of terrestrial vertebrates endemic to the TP and investigate the potential drivers of their spatio-temporal origins. Location Tibetan Plateau and its surrounding regions. Time period Cenozoic. Major taxa studied Terrestrial vertebrates. Methods We used dispersal-extinction-cladogenesis models based on time-calibrated phylogenies to reconstruct the ancestral ranges of 174 endemic TP species and compiled the ancestral ranges and age estimates of their dispersal events. We generated a possibility map of source areas for endemic TP species by counting the incidence of non-TP sister clades in 110 km x 110 km grid cells. We used generalized linear mixed models to assess the relative importance of historical processes and environmental factors in explaining the geographical variations in the source areas. We created subsets based on four vertebrate classes to test whether the dispersal events varied spatially and temporally among taxonomic groups. Results We found that the endemic species colonized the TP as early as 55 Ma, and that the main colonization phase started to increase around 15 Ma and peaked after 6 Ma. The major source areas of endemic TP species include the Hengduan Mountains, the Himalayas, and Central Asia. Elevation difference had the strongest effect on the source areas, followed by geographical distance. The spatio-temporal origins of species endemic to the TP and the potential drivers showed significant differences among vertebrate classes. Main conclusions Our study supports the hypothesis that endemic TP species originated from various zoogeographical regions at different times and highlights the important roles of the TP uplift and past climatic changes for determining the spatio-temporal origins of endemic TP species.

Automated summary

The study reveals that endemic species started to colonize the TP as early as 55 million years ago, with the main colonization phase increasing around 15 million years ago and peaking after 6 million years. The major source areas for endemic TP species include the Hengduan Mountains, the Himalayas, and Central Asia. Elevation difference has the strongest effect on the source areas, followed by geographical distance. Significant differences were found among vertebrate classes in terms of spatio-temporal origins and potential drivers of endemic TP species.