Evolutionary history of the angiosperm flora of China

A dated phylogeny and spatial distribution data for Chinese angiosperms show that eastern China has tended to act as a refugium for older taxa whereas western China has acted as a centre for their evolutionary diversification. A blossoming history of Chinese flora China is home to a vast range of flowering plants and has been seen as both a refuge for ancient lineages and a cradle for recent ones. Zhi-Duan Chen and colleagues examine the evolutionary history of Chinese flora and conclude that it is indeed both refuge and birthplace, but with a geographical twist. They find that 66% of Chinese flowering plant genera did not originate until the early Miocene (23 million years ago), but also uncover a distinct split between western and eastern China. Whereas lush, lowland eastern China tends to offer refuge for older genera, the rugged heights and harsh deserts of the west tend to be cradles for new evolutionary diversity. High species diversity may result from recent rapid speciation in a ‘cradle’ and/or the gradual accumulation and preservation of species over time in a ‘museum’ 1 , 2 . China harbours nearly 10% of angiosperm species worldwide and has long been considered as both a museum, owing to the presence of many species with hypothesized ancient origins 3 , 4 , and a cradle, as many lineages have originated as recent topographic changes and climatic shifts—such as the formation of the Qinghai–Tibetan Plateau and the development of the monsoon—provided new habitats that promoted remarkable radiation 5 . However, no detailed phylogenetic study has addressed when and how the major components of the Chinese angiosperm flora assembled to form the present-day vegetation. Here we investigate the spatio-temporal divergence patterns of the Chinese flora using a dated phylogeny of 92% of the angiosperm genera for the region, a nearly complete species-level tree comprising 26,978 species and detailed spatial distribution data. We found that 66% of the angiosperm genera in China did not originate until early in the Miocene epoch (23 million years ago (Mya)). The flora of eastern China bears a signature of older divergence (mean divergence times of 22.04–25.39 Mya), phylogenetic overdispersion (spatial co-occurrence of distant relatives) and higher phylogenetic diversity. In western China, the flora shows more recent divergence (mean divergence times of 15.29–18.86 Mya), pronounced phylogenetic clustering (co-occurrence of close relatives) and lower phylogenetic