Tectonic and climatic controls on plant biodiversity in the Hengduan Mountains, China

Mountainous regions contain some of the most dynamic landscapes in the world and host a majority of the world's biodiversity hotspots. The Hengduan Mountains, located at the syntax of Eurasia and India, have a complex geological history associated with a hyperdiverse assemblage of species. Tectonic, geomorphic and climatic processes in the Hengduan Mountains may have jointly caused the emergence of high biodiversity. We propose three mechanisms that may promote high-level montane biodiversity: habitat creation, habitat disruption and habitat oscillations. We mapped species richness patterns for seed plants and computed phylogenetic endemism across the entire Hengduan region. We developed a set of geomorphic metrics regarding these mechanisms to link plant richness and phylogenetic endemism patterns. By estimating the component of species richness that is attributable to habitat heterogeneity, we isolate the component that is the result of tectono-geomorphic processes. We found that regions of exceptionally high species richness are explained by a combination of habitat heterogeneity and tectono–geomorphic processes, whereas glaciation and high climate change velocity are associated with low richness, thus contributing to extinctions. We interpret the richness of biodiversity hotspots in the Hengduan Mountains in terms of climatic and tectonic processes.