The greater diversity of plant clades in the Neotropics compared to their relatives in Africa is a pervasive pattern in biogeography. To better understand the causes of this imbalance, Alcantara and colleagues studied the diversification dynamics of the monocot family Velloziaceae. In addition to being conspicuously richer in the Neotropics compared to the Palaeotropics, many species of Velloziaceae exhibit extreme desiccation tolerance (i.e. ‘resurrection’ behaviour), and other ecological specializations to life on rocky outcrops, poor sandy soils, open vegetation and seasonally dry climates. Velloziaceae is also ecologically dominant in the campos rupestres, a habitat having exceptionally high plant diversity and endemism in Brazil.
Using a time-calibrated molecular phylogeny, the authors estimate rates of diversification and test for the influence of geographic distribution and functional traits reflecting water-use strategies.
They find that high species richness of Velloziaceae in South America has been driven by faster diversification in lineages predominantly occurring in the campos rupestres. They propose this was the evolution of adaptive strategies in response to independent climatic events. The radiation of Vellozia in particular might have played a key role in the assembly of the campos rupestres vegetation.