Induced biotic response in Amazonian ant-plants: the role of leaf damage intensity and plant-derived food rewards on ant recruitment

Abstract

Although plant-ants respond to cues indicating the presence of herbivores, it remains unclear how ant workers are stimulated by herbivory cues with varying intensity. I hypothesized that ants respond more quickly to intense foliar damage, and ants inhabiting myrmecophytes that provide food resource recruit workers to any intensity of foliar damage. I tested the induced response in three ant-plant systems: two that provide food resources and another one that does not provide. I simulated leaf damage using different concentrations of foliar extracts. In all systems the plant-ant recruitment increased after damage simulations. In food providing system ants did not distinguish between different intensity damages, although one system have shown a mixed response to that intensity. This result indicates that ants defend more intensely their host plant to avoid damages that diminish food provisioning. In the non-food providing system ants responded more quickly to simulation of high foliar damage. This faster recruitment to leaves with high damage suggests that ants are searching for hot spots that potentially have more insects for feeding on. I suggested that future works could manipulate plant size and quality, and food provisioning to better understand why mutual ant-plant systems with very distinct characteristics are evolutionarily stabilized.

Keywords

• myrmecophytes
• herbivory
• protective mutualism
• Ant–plant interaction