Temporal variation has been one remarkable feature of ecological interactions. In ant–plant mutualism, this variation is widely known, although little is understood about the mechanisms that shape these variations. This study tested whether or not the phenology of extrafloral nectaries (EFNs) influences the temporal variation of two properties of an ant–plant interaction network. The network under investigation exhibited a nested pattern and low specialisation over most months. Monthly nestedness and specialisation in the network were negatively correlated, both being influenced by temporal variations in extrafloral nectar production of the plant community. The months of highest activity in the nectaries (August–November) were those when the level of generalisation in the network was at its highest. Although there were temporal variations in the properties of the network, the generalist core of the species remained the same over time. The stable core enhances the coevolutionary importance of ant–plant interactions for the community. Thus, it can be concluded that the phenology of EFNs is one effective mechanism shaping the temporal variation in ant–plant interaction.

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Extrafloral nectar is the main food source offered by plants to predatory ants in most land environments. Although many studies have demonstrated the importance of extrafloral nectaries (EFNs) to plant defense against herbivores, the influence of EFNs secretory activity pattern on predatory ants remains yet not fully understood. Here, we verified the relation between the extrafloral nectar production of a plant community in Cerrado in different times of the day, and its attractiveness to ants. The extrafloral nectaries (EFNs) of seven plant species showed higher productivity overnight. Ant abundance was higher in times of large extrafloral nectar production, however, there was no positive relation between ant richness on plants and EFNs productivity. There was temporal resource partitioning among ant species, and it indicates strong resource competition. The nectar productivity varied among plant species and time of the day, and it influenced the visitation patterns of ants. Therefore, EFNs are a key ant-plant interaction driver in the studied system.

Plant-animal interactions occur in a community context of dynamic and complex ecological interactive networks. The understanding of who interacts with whom is a basic information, but the outcomes of interactions among associates are fundamental to draw valid conclusions about the functional structure of the network. Ecological networks studies in general gave little importance to know the true outcomes of interactions and how they may change over time. We evaluate the dynamic of an interaction network between ants and plants with extrafloral nectaries, by verifying the temporal variation in structure and outcomes of mutualism for the plant community (leaf herbivory). To reach this goal, we used two tools: bipartite network analysis and experimental manipulation. The networks exhibited the same general pattern as other mutualistic networks: nestedness, asymmetry and low specialization and this pattern was maintained over time, but with internal changes (species degree, connectance and ant abundance). These changes influenced the protection effectiveness of plants by ants, which varied over time. Our study shows that interaction networks between ants and plants are dynamic over time, and that these alterations affect the outcomes of mutualisms. In addition, our study proposes that the set of single systems that shape ecological networks can be manipulated for a greater understanding of the entire system.

Interactions between ants and plants bearing extrafloral nectaries (EFNs) are among the most common mutualisms in Neotropical regions. Plants secrete extrafloral nectar, a carbohydrate‐rich food that attracts ants, which in return protect plants against herbivores. This ant–plant mutualism is subjected to temporal variation, in which abiotic factors can drive the establishment and frequency of such mutualistic interaction. However, studies investigating how abiotic factors (e.g. climate) directly and indirectly influence ant–plant–herbivore interactions are incipient. In this study, we investigated direct and indirect (via plant phenology) effects of temperature and rainfall on ant–plant–herbivore interactions. To address these goals, each month we estimated six plant phenophases (newly flushed leaves, fully expanded leaves, deciduousness, floral buds, flowers and fruits), the activity of EFNs and abundance of ants and herbivores in 18 EFN‐bearing plant species growing in a markedly seasonal region (the Brazilian Cerrado) during a complete growing season. Our results showed that (a) there were marked seasonal patterns in all plant phenophases, EFN activity and the abundance of ants and herbivores; (b) the peak of EFN activity and ant and herbivore abundance simultaneously occurred at the beginning of the rainy season, when new leaves flushed and (c) rainfall directly and indirectly (via changes in the production of new leaves) influenced EFN activity and this in turn provoked changes in ant abundance (but not on herbivores). Synthesis. Overall, our results build towards a better understanding of how climate drives seasonal patterns in ant–plant–herbivore interactions, explicitly considering plant phenology over time.

Plants allocate defences in order to decrease costs and maximize benefits against herbivores. The Optimal Defense Theory (ODT) predicts that continuously expressed (i.e. constitutive) defences are expected in structures of high value, whereas defences that are expressed or that increase their expression only after damage or upon risk of damage (i.e. induced defences) are expected in structures of low value. Although there are several studies evaluating ODT predictions, few studies have successfully tested them as a way of measuring ecological investment in extrafloral nectary (EFN)‐mediated ant–plant interactions. Here we compared extrafloral nectar production and ant attractiveness to EFNs located on vegetative versus reproductive plant structures on Qualea multiflora plants subjected to different levels of simulated herbivory. We then addressed the following predictions emerging from the ODT: (a) extrafloral nectar produced in inflorescence EFNs will have higher volumes and calories and will attract more ants than extrafloral nectar produced in leaf EFNs; (b) extrafloral nectar production (volume and calories) and ant attendance will increase after simulated herbivory in leaf EFNs but not in inflorescence EFNs; (c) higher simulated leaf herbivory will induce higher extrafloral nectar production in EFNs on leaves and (d) more attractive extrafloral nectar (higher volume and calories) will attract more ants. Extrafloral nectar volume and calorie content, as well as ant abundance, were higher in EFNs of inflorescences compared to EFNs of leaves both before and after simulated herbivory, consistent with one of our predictions. However, EFNs on both leaves and inflorescences, not on leaves only, were induced by simulated herbivory, a pattern opposite to our prediction. Plants subjected to higher levels of leaf damage produced more and higher calorie extrafloral nectar, but showed similar ant abundance. Finally, more attractive extrafloral nectar attracted more ants. Synthesis. Our results show that extrafloral nectar production before and after simulated herbivory, as well as ant recruitment, varies according to the plant structure on which EFNs are located. Our study is the first to show that ant recruitment via extrafloral nectar follows predictions from Optimal Defense Theory, and that the ant foraging patterns may be shaped by the plant part attacked and the level of damage it receives.

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