Mountains are among the most biodiverse areas on the globe. In young mountain ranges, exceptional plant species-richness is often associated to recent and rapid radiations linked to the mountain uplift itself. In ancient mountains, however, orogeny vastly precedes the evolution of vascular plants, so species-richness has been explained by species accumulation during long periods of low extinction rates. Here we evaluate these assumptions by analyzing plant diversification dynamicsin thecampo rupestre, an ecosystem associated to pre-Cambrian mountaintops and highlands of eastern South America, areas where plant species-richness and endemism are among the highest in the world. Analyses of 15 angiosperm clades show that radiations of endemics present fastest rates of diversification during the climatically unstable period of the last 5 million years. However, results from ancestral range estimations using different models disagree on the age of the earliest in situspeciation events and point to a complex floristic assembly. There is a general trend for higher diversification rates associated to these areas, but endemism may also increase or reduce extinction rates, depending on the group. Montane habitats, no matter their geological age, may lead to boosts in speciation rates by accelerating population isolation in archipelago-like systems, circumstances that can also result in higher extinction rates and fast species turnover, misleading age estimates of endemic lineages. 

14.05.20 Updated Mimosa dataset table (now this dataset also includes GenBank accession numbers)