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.

植物和蚂蚁进行多种互惠互动，有助于它们的适应性。然而，花朵中蚂蚁的存在可能会引起植物和传粉媒介之间的冲突。尽管蚂蚁和植物之间的相互作用在该地区无处不在，但在温带草原上对这些相互作用的研究很少。在这项研究中，我们调查了Eryngium chamissonis Urb上弓背蚁 (Emery) 蚂蚁的存在和活动性。影响昆虫造访该植物花朵的频率。我们构建了对比并使用广义线性混合模型进行了测试（I）花序中任何生物体的存在是否会减少昆虫的访问，（II）是否真的是蚂蚁的存在减少了访客的互动，以及（III）蚂蚁的行为是否对潜在减少访问量有更大的影响。我们发现，蚂蚁与E. chamissonis的相互作用影响了对花朵的访问次数，主要是减少了蜜蜂和苍蝇这两个主要群体的频率。无论蚂蚁的行为如何，这些影响都是一致的，这表明这些昆虫在花朵上的存在就可以改变花朵访客的频率。我们的工作是最早报告南美洲南部温带草原上蚂蚁和花朵之间相互作用的影响的工作之一。观察到的影响可能超出了捕食和资源竞争的简单风险，涉及这种蚂蚁与植物相互作用的更广泛的生态影响，包括对E. chamissonis繁殖的负面影响。