Ant-mediated seed dispersal: A few ant species (Hymenoptera: Formicidae) benefit many plants

Ants are ecosystems engineers, keystone species and incredibly abundant worldwide. A major cosmopolitan interaction between ants and plants is ant-mediated seed dispersal (myrmecochory). The interaction involves more than 11,000 plant species, but far fewer ant species, possibly just a few dozen keystone species worldwide. Researchers only began recognizing this degree of asymmetry in ant-mediated seed dispersal in recent years, and we explore the ecological and evolutionary implications of the changed perspective. We review what makes ants effective dispersers, how plants coevolve with ant partners, and how the interaction may benefit both participants. We suggest that morphological adaptations for myrmecochory have evolved repeatedly and independently in many plants lineages worldwide, and these trait adaptations likely select for effective seed dispersing ants. We propose that myrmecochory evolves and spreads only in ecosystems where the ant community includes potentially effective seed dispersers in high abundance. Furthermore, we hypothesize that the evolution and maintenance of the interaction only is possible where the distribution of traits between beneficial and antagonistic ants can fall under plant selection for the best partners.