Climate seasonality drives ant-plant-herbivore interactions via plant phenology in an extrafloral nectary-bearing plant community

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.

Automated summary

This study investigated the effects of temperature and rainfall on ant-plant-herbivore interactions, discovering that rainfall directly and indirectly influenced extrafloral nectar secretion activity, leading to changes in ant abundance, but not affecting herbivore levels. The results provide insight into how climate impacts seasonal patterns in these mutualistic interactions, emphasizing the importance of plant phenology.