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

Abstract

The early evolutionary pattern and molecular adaptation mechanism of alpine <i>Parnassius</i> 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 <i>Parnassius</i> 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 <i>Parnassius</i> formed a well-resolved basal clade, and the subgenera <i>Tadumia</i> and <i>Kailasius</i> were closely related in the phylogenetic trees. In addition, molecular dating analyses showed that the <i>Parnassius</i> 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 <i>Parnassius</i> species. Overall, our study provided some new insights into the spatiotemporally evolutionary pattern and high altitude adaptation of <i>Parnassius</i> butterflies from the extrinsic and intrinsic view, which will help to address evolution, biodiversity, and conservation questions concerning <i>Parnassius</i> and other butterfly species.