Post K-Pg rise in ant and termite prevalence underlies convergent dietary specialization in mammals

Ants and termites are ubiquitous members of most modern terrestrial ecosystems. These insects act as agents of selection among plants and animals, driving ecological and evolutionary shifts in disparate groups across the tree of life. Obligate consumers of ants or termites, called myrmecophages, exhibit morphological adaptations such as lengthened tongues and reduced teeth that are associated with a bulk feeding strategy. Though a typifying feature of some mammal lineages, the macroevolutionary history of obligate myrmecophagy and its relationship to social insect evolution is unknown. We report large-scale patterns of myrmecophagous evolution through a synthesis of the social insect fossil record, ant and termite evolutionary history, and mammal natural history data spanning 4,099 species. Specialized ant and termite feeding has arisen at least 12 times in mammals and through multiple pathways; transitions to myrmecophagy stem from insectivorous and carnivorous ancestors. We recover one reversal out of social insect feeding, perhaps owing to food source stability or difficulty in regaining generalist features. Despite the contemporary ubiquity of social insects, their history suggests a recent capacity for specialist consumers. While both lineages originated in the Cretaceous, rising fossil prevalence of ants and termites and their acquisition of large colony sizes predominantly occurred in the Cenozoic.