Large and thin leaves are compromised more by chewers

A major proportion of primary production is lost to insect herbivory. Leaf functional traits representing defense costs and palatability explain the intensity of herbivory at local scales. However, whether leaf traits explain herbivory at large scales needs clarification. By combining a leaf herbivory database and the TRY plant-trait database, we compared 190 species from 65 families across 45 sites in nine countries. We hypothesized that defensive and/or nutrient-poor leaves would compromise herbivory less globally. Both the absolute and percentage of maximum leaf-area loss were higher in the tropical zone. Larger leaves lost more disproportionate areas to chewer herbivores whenever phylogenetic signals were considered. Thin leaves with low leaf mass per area (LMA) and short lifespan were compromised more by herbivory based on the leaf trait syndrome. Although thin leaves were rich in nitrogen, phosphorus, and calcium, only leaf nitrogen marginally explained the loss of leaf area. The contribution of leaf area dominated the herbivory intensity among all other morphological and chemical traits. Overall, the benefits of chewers on herbivory were based on leaf area, because the loss of leaf biomass and nitrogen increased proportionally with its loss. Leaf construction costs, but not nutrient content, determined the intensity of herbivory globally. However, the overall percentage of loss in leaf area was not high, demonstrating the importance of elucidating the relationship between leaf functional traits and induced defense in future studies.