Senckenberg Biodiversity and Climate Research Centre (SBiK-F), Senckenberganlage 25, 60325, Frankfurt am Main, Germany.
Department of Integrative Biology, University of Guelph, Guelph, 50 Stone Road East, N1G 2W1, Ontario, Canada.
Nat Commun. 2020 Mar 27;11(1):1582. doi: 10.1038/s41467-020-15438-y.
Downsizing of animal communities due to defaunation is prevalent in many ecosystems. Yet, we know little about its consequences for ecosystem functions such as seed dispersal. Here, we use eight seed-dispersal networks sampled across the Andes and simulate how downsizing of avian frugivores impacts structural network robustness and seed dispersal. We use a trait-based modeling framework to quantify the consequences of downsizing-relative to random extinctions-for the number of interactions and secondary plant extinctions (as measures of structural robustness) and for long-distance seed dispersal (as a measure of ecosystem function). We find that downsizing leads to stronger functional than structural losses. For instance, 10% size-structured loss of bird species results in almost 40% decline of long-distance seed dispersal, but in less than 10% of structural loss. Our simulations reveal that measures of the structural robustness of ecological networks underestimate the consequences of animal extinction and downsizing for ecosystem functioning.
由于动物物种灭绝导致的动物群落小型化在许多生态系统中很普遍。然而，我们对于其对生态系统功能（如种子传播）的影响知之甚少。在这里，我们使用在安第斯山脉采集的八个种子传播网络，并模拟鸟类食果动物小型化如何影响结构网络的稳健性和种子传播。我们使用基于特征的建模框架来量化相对于随机灭绝的小型化对（作为结构稳健性的衡量标准）的交互数量和次生植物灭绝的后果，以及长距离种子传播（作为生态系统功能的衡量标准）。我们发现，小型化导致功能损失大于结构损失。例如，鸟类物种规模结构损失 10%，长距离种子传播减少近 40%，而结构损失不到 10%。我们的模拟表明，生态网络结构稳健性的衡量标准低估了动物灭绝和小型化对生态系统功能的影响。
