Genetic differentiation and evolutionary history of two medicinal gentians (Gentiana stipitata Edgew. and Gentiana szechenyii Kanitz) in the Qinghai-Tibet Plateau

Abstract

Understanding how alpine medicinal plants responded to environmental changes in the past may improve our ability to predict and mitigate the threats posed by global warming. The region of the Qinghai-Tibet Plateau (QTP) acted as a biogeographic source area and centre of diversification for Gentiana, but there, the genetic divergence and evolutionary processes underlying this diversification are still poorly understood. Focusing on two medicinal Gentiana species (Gentiana stipitata and G. szechenyii) in the QTP region, we assessed their genetic structure, demographic history and range shift to explore their genetic differentiation and evolutionary processes. Using both nuclear and plastid markers, high level of genetic differentiation was observed in both gentians. Both species showed signatures of recent population expansion. Furthermore, hybridization between G. stipitata and G. szechenyii was detected in one population. Species distribution modelling showed that both species continuously expanded range from the Last Interglacial to the present day. Divergence time estimates suggested that the onset of intraspecific diversification in the two gentians both occurred in the Late Miocene and the Pliocene. The results indicated that their intraspecific divergence should be related to topographical complexity and geological features of the Hengduan Mountains as well as geographical isolation in glaciations. This study outlines the patterns of genetic structure in two medicinal gentians, explores how these patterns are shaped, and provides insights into conservation management of medicinal gentians in the QTP region.