The Qinghai-Tibetan Plateau (QTP) is known as the Roof of the World, with an average altitude of 4,000 meters. Compared with low-elevation taxa, those species occurring on such high elevation experience extreme environmental conditions such as hypoxia, low temperatures and strong ultraviolet (UV) radiation. How these organisms adapt to the extreme environment of QTP has received great interests worldwide. Herein, we show that how the frogs (Amphibia, Dicroglossidae, Nanorana) and lizards (Reptilia, Agamidae, Phrynocephalus) have evolved a series of phenotypic, physiological and behavioral adaptations to counter the harsh condition on the QTP, i.e., the transition from oviparity to viviparity along the altitudes rises and the UV defense. By integrating omics data with functional validation research, we discovered genes related to UV defense and a corresponding temporal expression pattern in N. parkeri. Multiple defense genes (i.e., TYR for melanogenesis) exhibit positive selection with function-enhancing substitutions. By comparing differences in gene expression during the reproductive cycle, we revealed that the genetic basis of the evolution in reproductive behavior from oviparity to viviparity involved temporal and spatial changes in expression of appropriate genes (i.e., ESR1, PTGS2) that account for eggshell reduction or degeneration, placental development, delayed oviposition. Our work offers an improved understanding of evolution of organisms on the Roof of the world.
Adaptive evolution of amphibians and reptiles on the Qinghai-Tibetan Plateau (QTP)