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, we estimated six plant phenophases
(newly flushed leaves, fully-expanded leaves, deciduousness, floral buds,
flowers, and fruits) monthly, 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 (i) there were marked seasonal patterns in all
plant phenophases, EFN activity, and the abundance of ants and herbivores;
(ii) the peak of EFN activity and ant and herbivore abundance
simultaneously occurred at the beginning of the rainy season, when new
leaves flushed; and (iii) rainfall directly and indirectly (via changes in
theproduction of new leaves) influenced EFN activity and this in turn
provoked changes in ant abundance (but not on herbivores). Synthesis:
Overall, our results build toward a better understanding of how climate
drives seasonal patterns in ant-plant-herbivore interactions, explicitly
considering plant phenology over time.