Increasing social insect prevalence in the Cenozoic precipitated convergent dietary specialization among mammals

Ants and termites are ubiquitous members of most modern terrestrial ecosystems. These social insects have driven ecological change and evolution in disparate groups across the tree of life, acting as agents of selection among plants and animals. Even as individual ants and termites are rarely larger than a few millimeters, insect colonies make for highly concentrated population centers which can be exploited by predatory vertebrates. Because insects must be consumed in great numbers to sustain large predators, myrmecophages (obligate consumers of ants or termites) often exhibit dramatic morphological adaptations such as lengthened tongues and reduced teeth associated with efficiency achieving a bulk feeding strategy. To characterize the temporal and evolutionary history of myrmecophagy, we compiled dietary natural history data for 647 species of mammals, which we analyzed in a phylogenetic comparative framework. Specialized ant and termite feeding has arisen at least 12 times in mammals and through multiple pathways; transitions to myrmecophagy are equally common from insectivorous and omnivorous ancestors. The frequency and tempo of independent myrmecophagous origins increases following the K-Pg extinction and is concomitant with increases in diversity and relative abundance of ants and termites in the fossil record during the Cenozoic. Our results demonstrate the profound ecological impact of eusocial insects even through their own consumption.