The evolution and maintenance of biodiversity is largely determined by the interaction of genetics and environmental factors. Geological and climatic histories, which played pivotal roles in the evolution and maintenance of plant diversity in the Qinghai-Tibet Plateau (QTP) and adjacent regions, are the most important environmental aspects. We review the major effects of QTP environmental changes associated with geological uplift, Asian monsoon evolution, and Pleistocene climatic oscillation on the origin, evolution, population demography, and maintenance mechanisms of plant diversity in the QTP and adjacent regions across spatiotemporal scales. Furthermore, we summarize the current progress and knowledge gaps on mechanisms of diversification and maintenance of plant diversity, and outline the effect of climate change on plant genetic diversity, hybrid zone dynamics, plant diversity patterns, the effect of Asian Monsoon evolution on plant diversity maintenance, and mechanisms of community assembly, the five additional future research hotspots.