Environmental Sciences Department, Federal University of São Carlos, São Carlos, SP, Brazil.
School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK.
J Anim Ecol. 2024 Aug;93(8):1022-1035. doi: 10.1111/1365-2656.14121. Epub 2024 Jun 7.
Food webs depict the tangled web of trophic interactions associated with the functioning of an ecosystem. Understanding the mechanisms providing stability to these food webs is therefore vital for conservation efforts and the management of natural systems. Here, we first characterised a tropical stream meta-food web and five individual food webs using a Bayesian Hierarchical approach unifying three sources of information (gut content analysis, literature compilation and stable isotope data). With data on population-level biomass and individually measured body mass, we applied a bioenergetic model and assessed food web stability using a Lotka-Volterra system of equations. We then assessed the resilience of the system to individual species extinctions using simulations and investigated the network patterns associated with systems with higher stability. The model resulted in a stable meta-food web with 307 links among the 61 components. At the regional scale, 70% of the total energy flow occurred through a set of 10 taxa with large variation in body masses. The remaining 30% of total energy flow relied on 48 different taxa, supporting a significant dependency on a diverse community. The meta-food web was stable against individual species extinctions, with a higher resilience in food webs harbouring omnivorous fish species able to connect multiple food web compartments via weak, non-specialised interactions. Moreover, these fish species contributed largely to the spatial variation among individual food webs, suggesting that these species could operate as mobile predators connecting different streams and stabilising variability at the regional scale. Our results outline two key mechanisms of food web stability operating in tropical streams: (i) the diversity of species and body masses buffering against random and size-dependent disturbances and (ii) high regional diversity and weak omnivorous interactions of predators buffering against local stochastic variation in species composition. These mechanisms rely on high local and regional biodiversity in tropical streams, which is known to be strongly affected by human impacts. Therefore, an urgent challenge is to understand how the ongoing systematic loss of diversity jeopardises the stability of stream food webs in human-impacted landscapes.
食物网描绘了与生态系统功能相关的营养相互作用的复杂网络。因此，了解为这些食物网提供稳定性的机制对于保护工作和自然系统的管理至关重要。在这里，我们首先使用贝叶斯分层方法统一了三种信息来源（肠道内容物分析、文献汇编和稳定同位素数据）来描述热带溪流元食物网和五个单独的食物网。我们利用种群水平生物量和个体测量的体重数据，应用了一个生物能量模型，并使用洛特卡-沃尔泰拉系统的方程来评估食物网的稳定性。然后，我们使用模拟评估了系统对个别物种灭绝的恢复力，并研究了与更稳定系统相关的网络模式。该模型得出了一个稳定的元食物网，其中 61 个组成部分之间有 307 个链接。在区域尺度上，总能量流的 70%通过一组 10 个具有较大体重变化的类群发生。总能量流的其余 30%依赖于 48 个不同的类群，这表明对多样性社区有很大的依赖性。元食物网对个别物种灭绝具有较强的恢复力，具有能够通过弱的、非特化的相互作用连接多个食物网隔室的杂食性鱼类物种的食物网具有更高的恢复力。此外，这些鱼类物种对个体食物网之间的空间变化贡献很大，这表明这些物种可以作为移动捕食者连接不同的溪流，并在区域尺度上稳定变异性。我们的结果概述了热带溪流中两种关键的食物网稳定性机制：（i）物种和体重多样性缓冲随机和大小依赖干扰，（ii）高区域多样性和弱的杂食性捕食者相互作用缓冲物种组成的局部随机变化。这些机制依赖于热带溪流的高本地和区域生物多样性，而生物多样性已知受到人类影响的强烈影响。因此，一个紧迫的挑战是了解正在发生的多样性丧失如何危及受人类影响的景观中溪流食物网的稳定性。
