Data from: Removing interactions, rather than species, casts doubt on the high robustness of pollination networks

In the last 15 years, a complex networks perspective has been increasingly used in the robustness assessment of ecological systems. It is therefore crucial to assess the reliability of such tools. Based on the traditional simulation of node (species) removal, mutualistic pollination networks are considered to be relatively robust because of their 1) truncated power-law degree distribution, 2) redundancy in the number of pollinators per plant and 3) nested interaction pattern. However, species removal is only one of several possible approaches to network robustness assessment. Empirical evidence suggests a decline in abundance prior to the extinction of interacting species, arguing in favour of an interaction removal-based approach (i.e. interaction disruption), as opposed to traditional species removal. For simulated networks, these two approaches yield radically different conclusions, but no tests are currently available for empirical mutualistic networks. This study compared this new robustness evaluation approach based on interaction extinction versus the traditional species removal approach for 12 alpine and subalpine pollination networks. In comparison with species removal, interaction removal produced higher robustness in the worst-case extinction scenario but lower robustness in the best-case extinction scenario. Our results indicate that: 1) these two approaches yield very different conclusions and 2) existing assessments of ecological network robustness could be overly optimistic, at least those based on a disturbance affecting species at random or beginning with the least connected species. Therefore, further empirical study of plant–pollinator interactions in disturbed ecosystems is imperative to understand how pollination networks are disassembled.近十五年来，复杂网络（complex networks）视角愈发频繁地被应用于生态系统（ecological systems）的鲁棒性评估（robustness assessment），因此评估这类工具的可靠性至关重要。基于传统的节点（物种）移除（node (species) removal）模拟，互利传粉网络（mutualistic pollination networks）被认为具有相对较强的鲁棒性，原因在于三点：1）截断幂律度分布（truncated power-law degree distribution），2）每种植物的传粉者数量存在冗余（redundancy），3）嵌套式交互模式（nested interaction pattern）。然而，物种移除仅为网络鲁棒性评估的多种可行路径之一。实证证据（empirical evidence）表明，交互物种在灭绝前会出现丰度（abundance）下降，这支持采用基于交互移除的方法（即交互中断（interaction disruption）），而非传统的物种移除法。对于模拟网络（simulated networks）而言，这两种方法会得出截然不同的结论，但目前尚无针对实证互利传粉网络的相关测试。本研究针对12组高山亚高山传粉网络（alpine and subalpine pollination networks），对比了这种基于交互灭绝的新型鲁棒性评估方法与传统物种移除法的差异。相较于物种移除法，交互移除法在最坏灭绝情景（worst-case extinction scenario）下展现出更高的鲁棒性，但在最佳灭绝情景（best-case extinction scenario）下鲁棒性更低。我们的研究结果显示：1）两种方法会得出差异显著的结论；2）现有生态网络鲁棒性评估结果或许过于乐观，至少那些基于随机干扰物种或从连接度最低的物种开始的干扰的评估是如此。因此，针对受干扰生态系统（disturbed ecosystems）中的植物-传粉者互作（plant–pollinator interactions）开展进一步实证研究，对于理解传粉网络的瓦解机制至关重要。