The acacia ants revisited: convergent evolution and biogeographic context in an iconic ant/plant mutualism

Phylogenetic and biogeographic analyses can enhance our understanding of multispecies interactions by placing the origin and evolution of such interactions in a temporal and geographical context. We use a phylogenomicapproach—ultraconserved element sequence capture—to investigate the evolutionary history of an iconic multispecies mutualism: Neotropical acaciaants ( Pseudomyrmexferrugineus group) and their associated Vachelliahostplants. In this system, the ants receive shelter and food from the host plant, and they aggressively defend the plant against herbivores and competing plants. We confirm the existence of two separate lineages of obligate acaciaants that convergently occupied Vachelliaand evolved plant-protecting behaviour, from timid ancestors inhabiting dead twigsin rainforest. The more diverse of the two clades is inferred to have arisen in the Late Miocenein northern Mesoamerica, and subsequently expanded its range throughout much of Central America. The other lineage is estimated to hav...