Abstract
Karst ecosystems in southern China are species-rich and have high levels of endemism,yet little is known regarding the evolutionary processes responsible for theorigin and diversification of karst biodiversity. The genus Primulina (Gesneriaceae)comprises ca. 170 species endemic to southern China with high levels of ecological(edaphic) specialization, providing an exceptional model to study the plant diversificationin karsts. We used molecular data from nine chloroplast and 11 nuclearregions and macroevolutionary analyses to assess the origin and cause of speciesdiversification due to palaeoenvironmental changes and edaphic specialization in Primulina.We found that speciation was positively associated with changes in pasttemperatures and East Asian monsoons through the evolutionary history of Primulina.Climatic change around the mid-Miocene triggered an early burst followed by aslowdown of diversification rate towards the present with the climate cooling. Wedetected different speciation rates among edaphic types, and transitions among soiltypes were infrequently and did not impact the overall speciation rate. Our findingssuggest that both global temperature changes and East Asian monsoons have playedcrucial roles in floristic diversification within the karst ecosystems in southern China,such that speciation was higher when climate was warmer and wetter. This is thefirst study to directly demonstrate that past monsoon activity is positively correlatedwith speciation rate in East Asia. This case study could motivate further investigationsto assess the impacts of past environmental changes on the origin and diversificationof biodiversity in global karst ecosystems, most of which are under threat.