Urban bumblebees diversify their foraging strategy to maintain nutrient intake

Anthropogenic ecosystems can alter individual functions and ecological processes such as resource use and species interactions. While variability of morphological traits involved in diet and resource use has been observed between urban and non-urban populations of pollinators, the consequences on the dietary and pollen-transport patterns remain poorly understood. Here, we investigate the variability in the diet breadth of rural and urban individuals of two bumblebee species and the consequences for nutrient intake and pollen transport. We show that urban bumblebees exhibit a larger diet breadth than their rural counterparts, driven by the enhanced floral diversity in cities. However, we found that the nutrient intake remained similar across urban and rural ecosystems, indicating that bumblebees' foraging strategies can be adapted in terms of diet breadth to maintain intake and ratios of critical nutrients. We also found distinct pollen-transport patterns between urban and rural individuals, with urban individuals being more dissimilar than rural ones in the transported pollen both in the body and in the leg baskets. Our findings highlight the importance of considering complementary facets of species' diet and interactions when assessing the effects of anthropogenic ecosystems.