Miocene uplift and monsoon intensification coincided with avian diversification in the Himalaya-Hengduan Mountains

Mountains are well recognized for their exceptional high biodiversity, with rich aggregations of small-ranged species forming centers of endemism. The Himalaya- Hengduan Mountains adjacent to the Qinghai-Tibet Plateau, represent two of the world’s largest and most diverse temperate mountain systems, both categorized as global biodiversity hotspots. Previous studies have underscored its global importance in biodiversity conservation and the influence of environmental drivers on its current distribution patterns. However, a comprehensive understanding of avian assemblage dynamics over time in these regions remains elusive. In this study, we used the most up-to-date avian tree and reconstructed historical biogeographical models for 5392 species of 58 families, representing groups with distinct dispersal abilities, to examine the temporal patterns and avifaunal assembly mode (in situ speciation vs colonization) in these mountain systems, as well as their influence on the surrounding avifauna. We further estimate net diversification rates and compare them with palaeo-reconstructed East Asian summer monsoon precipitation trajectories. Our results revealed that modern avian assemblage in the Himalaya-Hengduan Mountains primarily began at the early-Oligocene and experienced rapid diversification during the Miocene, broadly overlapping with the inferred timing of the mountain uplift and the intensification of monsoon climates. In situ speciation has consistently remained the dominant driver of avian accumulation, but the speciation-colonization ratio varied across major clades and was associate with species’ dispersal ability. Our findings suggest that the Himalaya-Hengduan Mountains acted as a cradle for bird diversification, potentially driven by mountain uplift and the intensification of the Asian monsoon during the Neogene.