Theoretical models suggest that species abundance plays a crucial role in mutualism; high densities can lead to overexploitation. Additionally, mutualistic benefits are expected to increase under abiotic stress. We investigated the interplay between density dependence and abiotic factors in conditional mutualism, focussing on the interactions between yellow‐necked mice (Apodemus flavicollis) and common oaks (Quercus robur) across 3 years. We controlled for seed abundance, while mouse densities varied. Our approach included monitoring mouse abundance, measuring seed removal, determining the fate of harvested seeds and conducting seedling emergence trials to assess the advantages of seeds caching. We found that mouse abundance exerted a strong influence on all studied aspects of seed dispersal. Higher densities led to increased seed removal and greater dispersal distances. However, they also decreased the probability of seed caching and increased seed consumption, degrading dispersal quality and shifting the interaction towards antagonism. Furthermore, the reliance of seedling recruitment on burial varied over time, likely becoming more critical during dry conditions. This indicates that plants face the worst conditions when high abundance of mice coincides with abiotic stress. Synthesis: Our results supports the notion that increased rodent abundance reduces plant recruitment, revealing the conflicting interests of the interacting species. However, the dynamics of rodent–oak interactions are shaped not only by the density‐dependent foraging decisions of rodents, but also by the benefits of seed burial under stress. These findings illustrate how the interplay between population density and abiotic factors jointly dictate the costs and benefits of mutualistic interactions.

中文翻译：

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散居者的丰度和种子埋藏的优势驱动树木与啮齿动物相互作用的动力学


理论模型表明，物种丰度在互利共生中发挥着至关重要的作用。高密度可能导致过度开发。此外，在非生物胁迫下，互惠互利预计会增加。我们研究了条件互利共生中密度依赖性和非生物因素之间的相互作用，重点关注黄颈鼠 (Apodemus flavicollis) 和普通橡树 (Quercus robur) 之间三年来的相互作用。我们控制了种子丰度，而小鼠密度则不同。我们的方法包括监测小鼠丰度、测量种子去除量、确定收获种子的命运以及进行幼苗出苗试验以评估种子缓存的优势。我们发现小鼠丰度对种子传播的所有研究方面都产生了强烈影响。较高的密度导致种子去除量增加和传播距离更大。然而，它们也降低了种子储存的可能性并增加了种子消耗，降低了传播质量并使相互作用转向拮抗。此外，幼苗补充对埋葬的依赖随着时间的推移而变化，在干旱条件下可能变得更加重要。这表明当大量老鼠与非生物胁迫同时发生时，植物面临着最糟糕的条件。综合：我们的结果支持这样的观点，即啮齿动物丰度的增加会减少植物的补充，揭示了相互作用的物种之间的利益冲突。然而，啮齿动物与橡树相互作用的动态不仅取决于啮齿动物密度相关的觅食决策，还取决于压力下种子埋藏的好处。这些发现说明了人口密度和非生物因素之间的相互作用如何共同决定互利相互作用的成本和收益。