Species diversity and food web structure jointly shape natural biological control in agricultural landscapes

Land-use change and agricultural intensification concurrently impact
natural enemy (e.g., parasitoid) communities and their associated
ecosystem services (ESs), i.e., biological pest control. However, the
extent to which (on-farm) parasitoid diversity and food webs mediate
landscape-level influences on biological control remains poorly
understood. Here, drawing upon a 3-year study of quantitative
parasitoid-hyperparasitoid trophic networks from 25 different
agro-landscapes, we assess the cascading effects of landscape composition,
species diversity and trophic network structure on ecosystem functionality
(i.e., parasitism, hyperparasitism). Path analysis further reveals
causality leading to the biological control of a resident crop pest, i.e.,
Aphis gossypii. Functionality is dictated by (hyper)parasitoid diversity,
with its effects modulated by food web generality and vulnerability.
Non-crop habitat cover directly benefits biological control, whereas
secondary crop cover indirectly lowers hyperparasitism. Our work
underscores a need to simultaneously account for on-farm biodiversity and
trophic interactions when investigating ESs within dynamic
agro-landscapes.