Much effort has been devoted to understanding the function of extrafloral nectaries (EFNs) for ant-plant-herbivore interactions. However, the pattern of evolution of such structures throughout the history of plant lineages remains unexplored. In this study, we used the hypothesis of plant defense mediated by ants as a theoretical framework to test more specific hypotheses about the adaptive role of EFNs during plant evolution. Emphasis was given to different processes (neutral or adaptive) and factors (habitat...