jabbrv-ltwa-all.ldf jabbrv-ltwa-en.ldf Herbivory is one of the main biotic processes modulating plant diversity and productivity. In tropical forests, insects may remove up to 30% of total leaf biomass, but the effects on vegetation structure/productivity and biodiversity are poorly understood. Insect herbivory might promote or suppress plant growth, first reducing the photosynthetic area but also providing a rather direct path from nutrients in leaves to the plant-available soil pool. In this study, we used a trait-based Dynamic Global Vegetation Model (LPJ-GUESS-NTD), parameterized with unique field data from a tropical mountain forest gradient in southern Ecuador, to analyze how observed leaf-trait dependent insect herbivory influences the functional diversity and productivity of vegetation. According to the model, insect herbivory decreases net primary production by 6% and vegetation carbon storage by 26%. Herbivory also causes a vegetation community trait shift related to the leaf and wood economic spectrum, since with it specific leaf area (SLA) is reduced by 34% and wood specific gravity (WSG) increases by 10% respectively. This herbivory-induced change implies a shift towards a vegetation community with more conservative growth strategies, with negative effects on litter quality and nutrient availability. Accordingly, and in contrast to our expectations, herbivory reduces nutrient availability in the model. Finally, the inclusion of herbivory re-enforces gradients in nutrient availability and increases the community trait dissimilarity across altitudes (beta diversity). Our results suggest that insect herbivory has profound negative impacts on vegetation productivity and biomass in our study area, partly driven through feedbacks between soil processes and changes in plant traits. Furthermore, insect herbivory might be an important factor in shaping vegetation functional diversity.