Diversification in Ancient and Nutrient-Poor Neotropical Ecosystems: How Geological and Climatic Buffering Shaped Plant Diversity in Some of the World’s Neglected Hotspots

South America harbors the highest plant diversity on Earth. The causes of such exceptionally high diversity remain poorly understood, despite great attention devoted to the ecology and evolution of biota in productive and geologically recent ecosystems such as the Amazon forest and the Andes. Evidence suggests ancient and extremely nutrient-poor landscapes are major centers of plant diversity and endemism, and acted as interglacial refugia, but singularities of their evolutionary history have been overlooked. Here, we examine to what extent Ocbil theory (old, climatically-buffered, infertile landscapes) may prove useful in explaining diversification patterns in some of the most diverse Neotropical ecosystems. We propose a theoretical framework that encompasses a mechanistic explanation for the predictions of Ocbil theory, and links ecological and evolutionary processes to vegetation patterns and functional traits. We review diversification patterns and population genetics in campos rupestres vegetation in light of Ocbil theory. We propose areas of future research that will accelerate and improve our understanding on the ecology and evolution of Neotropical biota on ancient, nutrient-poor vegetation. This knowledge is expected to shed light on the complex history of Neotropical plant diversification and, ultimately, provide tools for their sustainable use and conservation.