Ant–Plant Mutualisms


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.

Keywords: ant‐garden; ant–plant; dispersal; domatium; elaiosome; extrafloral nectar; food body; indirect defence; myrmecophyte

Figure 1.

Obligate defensive ant–plant mutualisms. In the majority of obligate ant–plant mutualisms, specialised defensive ant species are housed and nourished by specialised myrmecophytes, which depend on the ant‐mediated defence for their survival. Ant‐exclusion experiments revealed similarly dramatic effects on leaf damage for Acacia hindsii in Mexico (a) with ants; (b) without ants; and for Macaranga bancana in Malaysia ((c), left plant with ants, right plant after six weeks of ant exclusion). Ants are nourished commonly by cellular food bodies (FBs) ((d), Pseudomyrmex gracilis worker harvesting an FB of Acacia cornigera) and extrafloral nectar (EFN) ((e), Pseudomyrmex peperi ants feeding on EFN of Acacia hindsii). FBs can be produced on different plant parts ((f), FBs on the pouches below leaf stalks of Cecropia mexicana; (g, i), FBs under recurved stipules of M. bancana and (h), FBs on upper surfaces of stipules of Macaranga hosei). In several systems where EFN is missing, scale insects are kept as a third partner ((g), Crematogaster sp. workers attending scale insects within the hollow twig of M. bancana, which serves as domatium in this species). Reproduced in part from Heil M , with permission from Wiley‐Blackwell.



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Heil, Martin(Sep 2010) Ant–Plant Mutualisms. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0022558]