Wojcik Laurie Anne, Ceulemans Ruben, Gaedke Ursula
Ecology and Ecosystem Modelling Group University of Potsdam Potsdam Germany.
Ecol Evol. 2021 Nov 4;11(22):15639-15663. doi: 10.1002/ece3.8214. eCollection 2021 Nov.
Biodiversity decline causes a loss of functional diversity, which threatens ecosystems through a dangerous feedback loop: This loss may hamper ecosystems' ability to buffer environmental changes, leading to further biodiversity losses. In this context, the increasing frequency of human-induced excessive loading of nutrients causes major problems in aquatic systems. Previous studies investigating how functional diversity influences the response of food webs to disturbances have mainly considered systems with at most two functionally diverse trophic levels. We investigated the effects of functional diversity on the robustness, that is, resistance, resilience, and elasticity, using a tritrophic-and thus more realistic-plankton food web model. We compared a non-adaptive food chain with no diversity within the individual trophic levels to a more diverse food web with three adaptive trophic levels. The species fitness differences were balanced through trade-offs between defense/growth rate for prey and selectivity/half-saturation constant for predators. We showed that the resistance, resilience, and elasticity of tritrophic food webs decreased with larger perturbation sizes and depended on the state of the system when the perturbation occurred. Importantly, we found that a more diverse food web was generally more resistant and resilient but its elasticity was context-dependent. Particularly, functional diversity reduced the probability of a regime shift toward a non-desirable alternative state. The basal-intermediate interaction consistently determined the robustness against a nutrient pulse despite the complex influence of the shape and type of the dynamical attractors. This relationship was strongly influenced by the diversity present and the third trophic level. Overall, using a food web model of realistic complexity, this study confirms the destructive potential of the positive feedback loop between biodiversity loss and robustness, by uncovering mechanisms leading to a decrease in resistance, resilience, and potentially elasticity as functional diversity declines.
生物多样性下降导致功能多样性丧失，这通过一个危险的反馈回路威胁着生态系统：这种丧失可能会阻碍生态系统缓冲环境变化的能力，进而导致生物多样性进一步丧失。在此背景下，人为导致的营养物质过量负荷频率增加，给水生系统带来了重大问题。以往研究功能多样性如何影响食物网对干扰的响应时，主要考虑的是至多具有两个功能不同营养级的系统。我们使用一个三营养级（因而更现实）的浮游生物食物网模型，研究了功能多样性对稳健性（即抵抗力、恢复力和弹性）的影响。我们将一个在各个营养级内无多样性的非适应性食物链，与一个具有三个适应性营养级的更多样化食物网进行了比较。通过猎物的防御/生长率与捕食者的选择性/半饱和常数之间的权衡，平衡了物种适应性差异。我们发现，三营养级食物网的抵抗力、恢复力和弹性会随着干扰规模的增大而降低，并且取决于干扰发生时系统的状态。重要的是，我们发现更多样化的食物网通常更具抵抗力和恢复力，但其弹性则取决于具体情况。特别是，功能多样性降低了向不良替代状态发生状态转变的概率。尽管动态吸引子的形状和类型具有复杂影响，但基础-中间相互作用始终决定了对营养脉冲的稳健性。这种关系受到现有多样性和第三营养级的强烈影响。总体而言，本研究使用一个具有现实复杂性的食物网模型，通过揭示随着功能多样性下降导致抵抗力、恢复力以及潜在弹性降低的机制，证实了生物多样性丧失与稳健性之间正反馈回路的破坏潜力。
