Ant behaviour as a mediator of extrafloral nectary‐based mutualisms: Interactions with nectar chemistry and environmental conditions

Abstract Ant–plant mutualisms mediated by extrafloral nectaries (EFNs) play a major role in plant defence, yet outcomes of these interactions are highly context‐dependent. Here, I review recent empirical evidence on three interlinked dimensions of these mutualisms, EFN chemistry, ant behaviour and environmental drivers, and examine how their interactions shape whether ant attendance produces net benefits or costs for plants. EFN composition is chemically complex and labile, responding to herbivory, phenology and abiotic stressors (e.g., drought, nutrient limitation), and these chemical traits influence ant recruitment and foraging. Ant species vary in recruitment ability, aggressiveness and dietary breadth, behaviours that predict protective efficacy but also the potential for pollination interference or attraction of exploiters (e.g., honeydew‐associated hemipterans). Environmental factors such as temperature extremes, fire regimes and habitat fragmentation further shape nectar production and ant assemblages, filtering interaction outcomes across space and time. I highlight key trade‐offs (resource allocation to rewards), reproductive costs via pollinator disruption and competition with hemipterans—and identify priority research directions: standardised EFN sampling and chemical/microbial analyses; factorial field experiments manipulating nectar traits and abiotic conditions; behavioural‐based assays across representative ant taxa; long‐term monitoring; explicit studies of microbial modification and EFN–honeydew dynamics; expanded geographic coverage; and development of mechanistic predictive models. Addressing these research priorities will improve our capacity to predict when EFN‐mediated ant attendance benefits plants and to apply that knowledge in conservation and restoration strategies.