Cenozoic vertebrate evolution and paleoenvironment in Tibetan Plateau: Progress and prospects

摘要

Due to its lofty height, the Tibetan Plateau features some of the harshest environments in the world with extreme coldness, low oxygen, high UV radiation, and in places, severe aridity. These harsh environments have served as the main driver of vertebrate evolution during the Cenozoic that produced a low productivity, low diversity, high endemicity community environmental forcing seems to be a dominant mechanism for mammalian evolution in marginal habitats. Mammals have acquired special adaptations for thermal insulation, oxygen transport, DNA damage repair, and others. While broadly similar to faunal assemblages in North China and Central Asia, Tibetan faunas often show initiation of cold-adapted lineages that predate Ice Age megafauna. Our "out of Tibet" hypothesis thus postulates that cold-tolerant species in Pliocene high Tibet were pre-adapted to conditions that were to become widespread during the subsequent Pleistocene Ice Age and Tibet had thus become a cradle for Ice Age megafauna. The best examples of the "out of Tibet" scenario include the Tibetan woolly rhinoceros (Coelodonta thibetana), Tibetan bharal (Pseudois), Asian hunting dog (Sinicuon), and ancestral snow leopard (Panthera blytheae). Our "Third Pole to North Pole" linkage of an extinct Pliocene Tibetan fox, Vulpes qiuzhudingi, with the late Pleistocene and extant arctic fox, Vulpes lagopus, is a subset of the "out of Tibet" hypothesis. One of the iconic Tibetan mammals, the endemic Tibetan antelope (Pantholops) has the longest residence in Tibet going back to the late Miocene, suggesting a long history of perfecting its adaptations to cold environments.