Functional roles of ants in a temperate grassland.

Ants in temperate grasslands are consumers and ecosystem engineers, influencing biodiversity and potentially grassland productivity. However, the effects of ant exclusion or suppression on resource removal and the biological community in temperate grasslands have yet to be fully explored. We conducted ant-suppression experiments and evaluated the effects of ants on ground-dwelling arthropod communities in the field by using pitfall and bait traps. In the laboratory, we evaluated the effects of ants on the ant-attended aphid Aphis rumicis, which is a honeydew resource for ants, and the slug (Deroceras laeve), an aphid predator. Aboveground arthropod communities were not affected by the ant-suppression treatment. However, slugs (D. laeve and Ambigolimax valentianus) visited bait resources more frequently in the ant-suppression treatment area. In the ant-absence condition in the laboratory experiment, there were fewer aphids on the plants compared to the ant-presence condition owing to predation by D. laeve. Our results suggest that ant abundance in temperate grasslands influences the predation activity of slugs toward honeydew sources such as aphids.