Timing, origins, and drivers of floristic diversity within a global biodiversity hotspot in eastern Asia

The Gaoligong Mountains (GLGM), forming the westernmost part of the Hengduan Mountains, is renowned for the high levels of plant species richness and endemism. However, the timing, biogeographic origins and underlying mechanisms that shaped the GLGM flora remain poorly understood. Here, we integrated molecular phylogenetic and historical biogeographic evidence from 197 well-studied genera to determine the temporal framework and biogeographic origins of this flora. To further resolve the evolutionary dynamics of its floristic elements, we assembled a comprehensive meta-phylogeny encompassing all 6205 taxa in the GLGM. Our results indicate that the GLGM flora originated no earlier than the Early Miocene. Notably, the accelerated diversification during the Late Miocene was profoundly driven by the intensification of the Asian monsoon. The flora developed from lineages of complex biogeographic origins, characterized by close affinities to both Gondwanan and Laurasian paleofloras. Furthermore, the GLGM flora had a tropical origin, accompanied with an increasing proportion of temperate elements under the climatic fluctuations since the Pliocene. Overall, Asian monsoon intensification and uplift of the Qinghai-Tibet Plateau since the Neogene have been key drivers of both lineage colonization and diversification, ultimately shaping the present GLGM flora. This study highlights the unique role of the GLGM in floristic interchange and provides new insights into the evolution of mountain biodiversity in Asia.