Stable‐ and radio‐isotopes and a bait‐choice experiment reveal changes in feeding habits of the ant community during primary succession

Abstract

Abstract Ants play important roles in trophic dynamics through their functions, ranging from herbivores to predators. However, little is known about whether the ant community modifies diet preferences and feeding habits during primary succession. We performed a bait‐choice experiment and analyses of stable carbon and nitrogen isotopes (δ13C and δ15N) and radiocarbon (Δ14C) of ants at four study sites that underwent primary succession on lava flows created by four volcanic eruptions approximately 70, 100, 230, and 540 years ago in Sakurajima, Japan. The ant community increasingly preferred plant‐based diets over animal‐based diets as the primary succession proceeded, likely because the ants attempted to balance nutrition through compensatory feeding according to diet availability. The δ13C values showed that the ants depended largely on carbon from C4 plants at the young sites with no canopy trees. The δ15N values of ants consistently differed among the species, suggesting that each species maintained the proportion of plant‐ and animal‐based diets during succession. The baseline‐corrected δ15N values of the ants were significantly higher at the youngest site than at the older sites; this probably reflects intraguild predation or reliance on aerial prey from surrounding older sites, which exhibited a higher δ15N‐baseline partly due to the colonisation of nitrogen‐fixing plants. The Δ14C values show that the two ant species examined had older diet ages, by approximately 2 years, at the old sites than those at the young sites, indicating their greater dependence on the detritus food web.