This study compiled a comprehensive database of 681 known ant-associated plant species. A model relying on GBIF-mediated occurrences estimates the real number of species at 1,140. An analysis of one type of ant-plant mutualism, in which plants have structures that hosts ants (domatia), suggests it may have evolved repeatedly due to parasitic relationships with scale insects. This adaptation may have started as early as the Miocene epoch, later than previously thought. The data also suggest that ant-plant symbioses have no straightforward effect on diversification rates in the host plants.
Chomicki, G., & Renner, S. S. (2015). Phylogenetics and molecular clocks reveal the repeated evolution of ant-plants after the late Miocene in Africa and the early Miocene in Australasia and the Neotropics. The New Phytologist, 207(2), 411–425. doi:10.1111/nph.13271