Vertebrate predators as hidden players in ant-plant mutualisms: costs, resistance, and recovery.

Ant-plant mutualisms are typically framed as two-species exchanges in which plants provide food and shelter in return for herbivore defense. Yet ants are themselves valuable prey, potentially attracting vertebrate predators that impose hidden structural costs on host plants. Here, I argue that such interactions incur partner-associated indirect costs: plants may suffer damage not from their partners directly, but because those partners attract vertebrate predators. Using the Azteca-Cecropia mutualism as a focal example, I synthesize evidence that anteaters and woodpeckers excavate ant-occupied stems and internodes, producing mechanical damage while targeting the ants. I then develop a framework for understanding how ant-plant systems respond to recurrent predator disturbance through resistance (traits that reduce attack success) and recovery (traits that restore function after damage). Resistance traits include aggressive colony defense and protective architecture, whereas recovery traits include plant regrowth, ant-mediated wound repair, and microbial reinforcement of nest structures. Integrating these responses across ecological and evolutionary timescales generates predictions linking individual attack outcomes to population dynamics, ecosystem processes, and the diversification of convergent ant-plant lineages.