Miocene Diversification and High-Altitude Adaptation of Butterflies (Lepidoptera: Papilionidae) in Qinghai-Tibet Plateau Revealed by Large-Scale Transcriptomic Data.

The early evolutionary pattern and molecular adaptation mechanism of alpine butterflies to high altitudes in Qinghai-Tibet Plateau are poorly understood up to now, due to difficulties in sampling, limited sequence data, and time calibration issues. Here, we present large-scale transcriptomic datasets of eight representative species to reveal the phylogenetic timescale and potential genetic basis for high-altitude adaptation with multiple analytic strategies using 476 orthologous genes. Our phylogenetic results strongly supported that the subgenus formed a well-resolved basal clade, and the subgenera and were closely related in the phylogenetic trees. In addition, molecular dating analyses showed that the began to diverge at about 13.0 to 14.3 million years ago (middle Miocene), correlated with their hostplant's spatiotemporal distributions, as well as geological and palaeoenvironmental changes of the Qinghai-Tibet Plateau. Moreover, the accelerated evolutionary rate, candidate positively selected genes and their potentially functional changes were detected, probably contributed to the high-altitude adaptation of species. Overall, our study provided some new insights into the spatiotemporally evolutionary pattern and high altitude adaptation of butterflies from the extrinsic and intrinsic view, which will help to address evolution, biodiversity, and conservation questions concerning and other butterfly species.