Data from: Ants on flowers: Protective ants impose a low but variable cost to pollination, moderated by location of extrafloral nectaries and type of flower visitors

Throughout their lifetimes, individuals of most species engage in multiple
mutualistic interactions simultaneously. These mutualisms can interfere
with each other, leading to ecological costs that can influence the
outcome of these interactions. Identifying factors that modulate these
costs is pivotal to reaching a deeper understanding of the dynamics of
mutualistic interactions. We investigated the ecological costs of
protective ants on the pollination of plants with extrafloral nectaries
(EFNs) and how plant traits and the type of pollinator can modulate them.
We hypothesized that (1) ants negatively affect the patterns of flower
visitation and plant reproductive performance and that (2) this effect is
relatively higher for plants bearing EFNs close to inflorescences compared
to those bearing EFNs only on vegetative tissues. Additionally, we
hypothesized that (3) the effect of ants on flower visitation is
contingent upon the type of flower visitor. To evaluate these hypotheses,
we used a meta-analytical approach based on 27 studies that assessed the
effects of ants on patterns of floral visitation and plant reproductive
performance. We found that ants impose a low, yet highly variable, cost to
pollination. Specifically, ants have a strong negative effect on patterns
of flower visitation, especially when the visitors are bees, but this does
not translate into reduced plant reproductive performance. The
reproductive success of plants with EFNs close to vegetative tissue is
enhanced by ant presence. Finally, the negative effect of ants on flower
visitors is stronger when EFNs are closer to inflorescences. Synthesis:
Our results indicate that, in general, ants have a low impact on the
pollination of EFN-bearing plants. This pattern supports theoretical
predictions that natural selection acts to lower the costs of protection
mutualisms. Our macroscale evaluation further shows that plant traits such
as EFN location, as well as the type of flower visitors, modulate this
cost. The outcome of ant-pollinator interactions may affect the
evolutionary trajectory of traits mediating defense and pollination in
EFN-bearing plants.