Herbivory on the pedunculate oak along an urbanization gradient in Europe: effects of impervious surface, local tree cover and insect feeding guild

Urbanization is recognized as an important driver of the diversity and abundance of tree associated insect herbivores, but its consequences for insect herbivory are controversial. A likely source of variability among studies is the insufficient consideration of intra-urban variability in forest cover. With the help of citizen scientists, we investigated the independent and interactive effect of urbanization and local canopy cover on insect herbivory in the pedunculate oak (Quercus robur) throughout most of its geographic range in Europe. We found that the damage caused by chewing insect herbivores as well as the incidence of leaf-mining and gall-inducing herbivores consistently decreased with increasing urbanization around focal oaks. Herbivory by chewing herbivores increased with increasing forest cover, regardless of urbanization. In contrast, an increase in local canopy cover buffered the negative effect of urbanization on leaf-miners and strengthened its effect on gall-inducers. The...城市化被公认为调控树木关联昆虫植食者多样性与种群丰度的重要驱动因子，但其对昆虫植食作用的影响仍存在争议。现有研究间结论存在差异的一个关键诱因，是未充分考量城区内森林覆盖度的空间异质性。本研究借助公民科学家的力量，针对欧洲境内绝大多数分布区域内的夏栎（Quercus robur），探究了城市化与局部冠层覆盖度对昆虫植食作用的独立效应与交互效应。研究发现，围绕样株栎树的城市化水平提升时，咀嚼式昆虫植食者造成的叶片损伤，以及潜叶性、虫瘿诱导性植食者的发生比例均持续下降。无论城市化水平如何，咀嚼式植食者的植食作用均随森林覆盖度提升而增强。与之相反，局部冠层覆盖度的提升可缓解城市化对潜叶性植食者的负面影响，并强化其对虫瘿诱导性植食者的作用效应。