Noah Just, Jana Eva Schön, Annemarie Wurz, Jürgen Homeier, Jörg Bendix, Nina Farwig, Roland Brandl

Arthropod herbivores modulate ecosystem structure, productivity, and nutrient cycling. While previous work has shown that plant-herbivore interactions for individual species are shaped by abiotic factors, traits, and the surrounding plant community, the relative contribution of abiotic and biotic factors for herbivory at the community level remains elusive. Here, we use a structural equation model to disentangle the relative impact of temperature, precipitation (i.e., abiotic factors), tree phylogenetic diversity, and chemical as well as morphological leaf traits on total leaf herbivory in the tree canopy. Leaf area loss was estimated along an elevational gradient from 1000 to 3000 m a.s.l. in a tropical rainforest in southern Ecuador using litter traps. Community leaf herbivory ranged from 2.5 % at 3000 m to 3.4 % at 1000 m. Community leaf herbivory decreased with elevation, indirectly linked to increasing phylogenetic diversity and directly to lower specific leaf area, calcium, and iron concentrations in plants. Our results suggest that community leaf herbivory depends primarily on biotic interactions, which implies that variations in these interactions, e.g., through climate or land-use change, could cause a shift in the structure or productivity of the whole ecosystem.