Wróbel Aleksandra, Zduniak Milena, Neuschulz Eike Lena, Zwolak Rafał
Department of Zoology, Poznań University of Life Sciences, Poznań, Poland.
Mammal Research Institute, Polish Academy of Sciences, Białowieża, Poland.
J Anim Ecol. 2025 Jul 2. doi: 10.1111/1365-2656.70101.
Abiotic factors have traditionally been considered the primary determinants of species' range limits and responses to climate change. However, growing evidence shows that biotic interactions, such as seed predation and dispersal, also play crucial roles in shaping plant distributions and influencing range shifts. We investigated how scatterhoarding rodents affect the recruitment of Swiss stone pine (Pinus cembra) at its upper altitudinal limits in the Swiss Alps. We focused on interactions between the pine and the rodent community, exploring how these interactions can potentially affect the effectiveness of seed dispersal by the spotted nutcracker (Nucifraga caryocatactes). We conducted seed crop estimation, rodent live-trapping, seed tracking experiments and seedling emergence trials across an altitudinal gradient over 3 years. We tested three hypotheses: (1) rodents cache a considerable portion of removed seeds, including those pilfered from nutcracker caches, in favourable microsites; (2) rodents consume seeds from nutcracker caches, impeding pine recruitment; and (3) the role of rodents varies with seed availability and rodent abundance, shifting between mutualism and antagonism. Rodents acted consistently as seed predators and cache pilferers. In seed tracking experiments, they consumed 97% of the seeds they removed and cached only 3%. In cache pilferage experiments, rodents reduced seedling emergence from simulated caches by two-thirds. These findings support hypothesis (2), indicating that rodents suppress Swiss stone pine recruitment by reducing the effectiveness of nutcracker-mediated seed dispersal. The negative impact was most pronounced when rodent populations were high and seed availability was low, aligning with the concept of predator satiation. Our study suggests that climate warming, which is expected to increase rodent abundances at higher altitudes, may intensify the negative effects of rodents on pine recruitment, impeding the upward migration of Swiss stone pine. These findings stress the importance of including biotic interactions, particularly seed predation and interspecific seed pilferage, into ecological models to improve predictions of ecosystem responses to environmental changes. Understanding these dynamics is crucial for developing effective conservation strategies in the face of climate change.
传统上，非生物因素一直被视为物种分布范围限制和对气候变化响应的主要决定因素。然而，越来越多的证据表明，生物相互作用，如种子捕食和传播，在塑造植物分布和影响分布范围变化方面也起着关键作用。我们研究了分散贮藏种子的啮齿动物如何影响瑞士阿尔卑斯山海拔上限处瑞士石松（Pinus cembra）的更新。我们重点关注了松树与啮齿动物群落之间的相互作用，探讨了这些相互作用如何可能影响斑尾榛鸡（Nucifraga caryocatactes）种子传播的有效性。我们在三年时间里，沿着海拔梯度进行了种子产量估计、啮齿动物活体诱捕、种子追踪实验和幼苗出土试验。我们测试了三个假设：（1）啮齿动物会将相当一部分被搬走的种子，包括从榛鸡贮藏处偷来的种子，贮藏在适宜的微生境中；（2）啮齿动物会吃掉榛鸡贮藏处的种子，从而阻碍松树的更新；（3）啮齿动物的作用会随着种子可获得性和啮齿动物数量的变化而变化，在互利共生和拮抗作用之间转变。啮齿动物一直充当种子捕食者和贮藏处偷窃者。在种子追踪实验中，它们吃掉了97%被搬走的种子，只贮藏了3%。在贮藏处偷窃实验中，啮齿动物使模拟贮藏处的幼苗出土率降低了三分之二。这些发现支持了假设（2），表明啮齿动物通过降低榛鸡介导的种子传播有效性来抑制瑞士石松的更新。当啮齿动物数量多且种子可获得性低时，负面影响最为明显，这与捕食者饱足的概念相符。我们的研究表明，预计会使高海拔地区啮齿动物数量增加的气候变暖，可能会加剧啮齿动物对松树更新的负面影响，阻碍瑞士石松向上迁移。这些发现强调了将生物相互作用，特别是种子捕食和种间种子偷窃纳入生态模型以改善对生态系统对环境变化响应预测的重要性。了解这些动态对于在面对气候变化时制定有效的保护策略至关重要。
