Ant–Plant Mutualisms

Abstract

Abstract Ants and plants are engaged in thousands of mutualisms, which can be categorised in two major groups: dispersal and defence mutualisms. Myrmecochory, the dispersal of plant seeds by ants, is usually facilitated by the elaiosome, an appendix of the seed that is used as a reward. Because elaiosomes represent a nutritional supplement rather than a full diet, dispersal mutualisms are facultative ones. Only in ant‐gardens, the ants use the dispersed epiphytes as support to construct their carton nests, and these mutualisms tend to be obligate ones. In facultative defensive mutualisms, plants provide ant rewards, such as cellular food bodies (FBs) or extrafloral nectar (EFN), to foraging ants that serve as an indirect defence against herbivores. Obligate defensive mutualisms, by contrast, are based on the provisioning of nesting space. Ants dominate most terrestrial ecosystems. Owing to their mobility and social structure, they appear perfect partners for plant dispersal and defence. Key Concepts: Plants can benefit from indirect defence that is mediated through the third trophic level. Ants are the dominant animal group in terrestrial ecosystem and – being common predators – have a high potential to defend plants against herbivores. Plants can provide food resources or nesting space to ants in order to increase their presence and capacity to function as defenders. Ants can also transport seeds and thereby function in dispersal. Obligate ant–plant mutualisms reach high levels of reciprocal specialisations. The evolutionary origins of most interactions remain to be investigated.