Experimental warming increases herbivory by leaf-chewing insects in an alpine plant community.

Climate warming is predicted to affect species and trophic interactions worldwide, and alpine ecosystems are expected to be especially sensitive to changes. In this study, we used two ongoing climate warming (open-top chambers) experiments at Finse, southern Norway, to examine whether warming had an effect on herbivory by leaf-chewing insects in an alpine heath community. We recorded feeding marks on the most common vascular plant species in warmed and control plots at two experimental sites at different elevations and carried out a brief inventory of insect herbivores. Experimental warming increased herbivory on and also experienced increased herbivory at the lower and warmer site, indicating an overall positive effect of warming, whereas experienced an increased herbivory at the colder and higher site indicating a mixed effect of warming. The Lepidoptera and were the two most common leaf-chewing insects in the heath. Based on the observed patterns of herbivory, the insects life cycles and feeding preferences, we argue that is the most important herbivore on and the most important herbivore on . We conclude that if the degree of insect herbivory increases in a warmer world, as suggested by this study and others, complex interactions between plants, insects, and site-specific conditions make it hard to predict overall effects on plant communities.