Resource limitation in intensively managed agricultural ecosystems compromises reproductive success and increases wing asymmetry in bumble bees

Agricultural intensification reduces the diversity and continuity of floral resources, exposing pollinators to multiple stressors. Although resource limitation is a key driver of pollinator declines, the mechanisms linking environmental conditions to pollinator performance remain unclear. We tested whether alleviating food limitation improves bumble bee colony performance and whether agricultural intensification constrains worker development and reproduction. We hypothesised that supplemental nutrition would enhance colony performance, particularly by reducing developmental instability and enhancing reproductive success, whereas agricultural intensification would negatively affect worker development and reproduction. We placed Bombus terrestris colonies across 24 locations spanning a gradient of agricultural cover and experimentally supplemented a subset with pollen and nectar. We quantified worker body size, wing asymmetry, and reproductive output in relation to supplementation, agricultural cover and floral resources. Food supplementation did not increase body size but reduced wing asymmetry and enhanced reproductive output, indicating that nutritional stress constrains developmental stability and colony fitness. Worker body size declined with increasing agricultural cover across treatments, suggesting a consistent developmental cost of landscape intensification that was not alleviated by additional food provisioning. Furthermore, we found weak evidence for a positive effect of agricultural cover on wing asymmetry and of floral diversity on reproductive success across treatments. These results demonstrate trait-specific responses to environmental stress: nutritional limitation primarily constrains developmental stability and reproduction, whereas worker body size appears to be more strongly shaped by landscape-level conditions. This highlights the importance of maintaining sufficient and continuous floral resources to support pollinator populations in intensively managed agricultural systems.