Moderation is best: effects of grazing intensity on plant-flower visitor networks in Mediterranean communities

The structure of pollination networks is an important indicator of ecosystem stability and functioning. Livestock grazing is a frequent land use practice that directly affects the abundance and diversity of flowers and pollinators and, therefore, may indirectly affect the structure of pollination networks. Here we studied how grazing intensity affected the structure of plant-flower visitor networks along a wide range of grazing intensities by sheep and goats, using data from 11 Mediterranean plant-flower visitor communities from Lesvos Island, Greece. We hypothesized that intermediate grazing might result in higher diversity as predicted by the Intermediate Disturbance Hypothesis, which could in turn confer more stability to the networks. Indeed, we found that networks at intermediate grazing intensities were larger, more generalized, more modular, and contained more diverse and even interactions. Despite general responses at the network level, the number of interactions and selectivene...传粉网络（pollination networks）的结构是生态系统稳定性与功能运行的重要指示指标。牲畜放牧是一种常见的土地利用方式，可直接影响花卉与传粉者的丰度及多样性，进而间接改变传粉网络的结构。本研究依托希腊莱斯沃斯岛（Lesvos Island）11个地中海植物-访花者群落的调查数据，探究了绵羊与山羊的多梯度放牧强度对植物-访花者网络结构的影响。我们提出假说：依据中度干扰假说（Intermediate Disturbance Hypothesis），中度放牧可提升群落多样性，进而增强传粉网络的稳定性。研究结果证实了这一推测：中度放牧强度下的传粉网络规模更大、泛化程度更高、模块化结构更显著，且交互作用的多样性与均匀性均更为突出。尽管在网络整体层面呈现出一致的响应规律，但交互作用数量与选择性……