Beyond nectar: exploring the effects of ant presence on the interaction of flower visitors of a rosette in grassland

Abstract

Plants and ants engage in diverse mutualistic interactions that contribute to their adaptive fitness. However, the presence of ants in flowers can generate conflicts between plants and pollinators. These interactions are little studied in temperate grasslands, despite the ubiquitous interactions between ants and plants in this region. In this study, we investigated how the presence and mobility of Camponotus termitarius (Emery) ants on Eryngium chamissonis Urb. affect the frequency of insect visitation on the flowers of this plant. We constructed contrasts and tested using generalized linear mixed models (I) whether the presence of any organism in the inflorescences decreases insect visitation, (II) whether it is really the presence of ants that decreases visitor interaction, and (III) whether the ant behavior has a greater effect on potentially reducing visits. We showed that the interaction of ants with E. chamissonis affected the number of visits to flowers, mainly reducing the frequency of the two main groups, bees and flies. These effects were consistent regardless of the ants' behavior, indicating that the mere presence of these insects on flowers can alter the frequencies of floral visitors. Our work is one of the first to report the effects of the interaction between ants and flowers in temperate grasslands in southern South America. The observed effects may go beyond the simple risk of predation and competition for resources, involving broader ecological implications for this ant–plant interaction, including a negative impact on the reproduction of E. chamissonis.