Foraging ants on the extrafloral nectaries repel nectar thieves but not the effective pollinator of Vigna luteola (Fabaceae) in a Mexican coastal sand dune

While some studies have shown that ants that visit extrafloral nectaries may defend their host plants against potential herbivores, recent researches have shown that such ant-plant mutualism may be broken in some cases. For example, the presence of ants on plants could also drive away pollinators and seed dispersers. However, it is not yet known what mechanisms could favor that ant presence on plants does not affect other mutualistic interactions involving plants. In this work, we performed a series of field experiments to test the hypothesis that the presence of ants on EFNs located at the base of the inflorescences of Vigna luteola (Fabaceae) may have a negative effect on floral visitors but not on potential pollinators in a Mexican coastal sand dune. In general, we found that the presence of ants on the plants decreased the rate of flower visitation. However, we observed that the time of visitation of the effective pollinators the bee ( Pseudocentron) sp. on the flowers was less compared to that of other floral visitors. This strategy may allow that ants cannot aggressively scare away the effective pollinators. In summary, we show that the effective pollinators of V. luteola present strategies that allow them to visit the flowers without being aggressively attacked by the ants that visit the extrafloral nectaries (EFNs). Therefore, the presence of ants on plants could have a dual function: protecting plants against potential herbivores as well as, filtering flowers against nectar thieves.