Herbivory on the pedunculate oak along urbanization range in Europe:
effects of local forest cover and insect feeding guild
Abstract
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. 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. These results show the complexity of plant-herbivore
interactions in urbanized areas, highlighting that the presence of local
canopy cover within cities has the potential to attenuate or modify the
effect of urbanization on biotic interactions.