Data from: Trophic interactions in an ant nest microcosm: a combined experimental and stable isotope (δ13C/δ15N) approach.

Living in close association with other organisms has proven to be a widespread and successful strategy in nature. Some communities are completely driven by symbiotic associations and therefore, intimate relationships among the partners can be expected. Here, we analyzed in-depth the food web of a particularly rich community of arthropods found in strict association with European red wood ants (Formica rufa group). We studied the trophic links between different ant-associated myrmecophiles and food sources associated with the host ant, but also tested predator-prey links among myrmecophiles themselves. Our approach combined direct feeding tests and stable carbon and nitrogen isotope analyses for a large number of myrmecophiles. The results of the direct feeding tests reveal a complex food web. Most myrmecophiles were found to parasitize on ant brood. Moreover, we encountered multiple trophic predator-prey links among the myrmecophiles. The results of the stable isotope analyses complement these findings and indicate the existence of multiple trophic levels and trophic isotopic niche compartmentalization. δ15N values were strongly correlated with the trophic levels based on the direct tests, reflecting that δ15N values of myrmecophiles increased with higher trophic levels. This strong correlation underlines the strength of stable isotopes as a powerful tool to assess trophic levels. In addition, the stable isotope data suggest that most species only facultatively prey on ant brood. The presence of numerous trophic interactions among symbionts clearly contrasts with the traditional view of social insects nests as offering an enemy-free space for symbionts. Interestingly, the ant host can indirectly benefit from these interactions because brood predators are also preyed upon by other myrmecophiles. Overall, this study provides unique insights into the complex interactions in a small symbiont microcosm system and suggests that the interactions between host and symbiont might be mediated by other symbionts in the same community.

与其他生物形成紧密共生关联，已被证实是自然界中广泛存在且行之有效的生存策略。部分生物群落完全由共生关系主导，因此其群落成员间可预期存在紧密的互作关系。本研究针对一类与欧洲红褐林蚁（Formica rufa group）形成严格共生关系的丰富节肢动物群落，深入解析了其食物网结构。我们不仅探究了不同蚁栖生物（myrmecophile）与宿主蚁相关食物源之间的营养联系，还检测了蚁栖生物彼此间的捕食-被捕食关系。本研究结合了针对大量蚁栖生物的直接饲喂实验与稳定碳、氮同位素分析技术。直接饲喂实验结果表明该食物网结构复杂，多数蚁栖生物被证实以寄生方式取食蚁类幼虫。此外，我们还观测到蚁栖生物间存在多条营养级捕食-被捕食联系。稳定同位素分析结果佐证了上述发现，并表明该群落存在多个营养级以及营养同位素生态位的分隔现象。蚁栖生物的δ15N值与直接实验得出的营养级呈显著正相关，这表明其δ15N值随营养级升高而升高。这一显著相关性进一步证实了稳定同位素技术作为评估营养级有效工具的可靠性。此外，稳定同位素数据显示，多数蚁栖生物仅兼性捕食蚁类幼虫。共生体间存在大量营养互作的现象，与传统认知中"社会性昆虫巢穴为共生体提供无天敌生存空间"的观点形成鲜明对比。值得注意的是，宿主蚁可通过这些互作间接获益：因为捕食蚁幼虫的生物同时也会被其他蚁栖生物捕食。综上，本研究为解析小型共生体微宇宙系统中的复杂互作关系提供了独特视角，并表明宿主与共生体间的互作可能由群落内其他共生体所介导。