The impact of dietary breadth on bumblebee colony fitness

The current decline of pollinators may disrupt ecosystems and ecosystem services with potentially harmful effects on nature and human society. While the importance of habitat loss and fragmentation, pollution and increased disease risk in driving pollinator decline has been clearly demonstrated, the impact of resource diversity is less well understood. In this study, we investigated the effect of pollen diversity and composition on reproductive success and fitness of Bombus terrestris colonies. We asked the question whether a higher plant diversity results in a more diverse diet, lower pathogen incidence and a higher colony fitness. To answer these questions, colonies of lab-reared bumblebees were placed in species-poor heathland and species-rich semi-natural grasslands that strongly differed in plant community composition and diversity. We examined pollen loads on the bodies of foragers and identified the plant taxa present in the realized diet via DNA metabarcoding of the ITS2 marker...., Colony performance
After collection of the hives at the end of the experiment, all bumblebees were killed and stored at -20°C to conserve the hives’ structure. All hives were dissected, and individual caste members were counted. The number of queens, workers, males, regular pupae and queen pupae were counted to assess colony development. The production of sexuals is mainly indicative for colony performance and directly related to fitness. Therefore, the total number of queens (emerged and pupae), the number of males, and the ratio of gynes:males was used as proxy for colony performance. A higher ratio in the latter indicates better colony performance because of the higher overall investment in queens than males (Duchateau et al, 2004). In addition, we recorded other information such as colony net weight gain, presence of involucrum, and the weight of the pollen mass stored in the pollen pots inside the colony.
DNA metabarcoding of pollen samples
Pollen DNA was extracted using the Norgen..., See README file. There are separate files for each section above. R code refers to any of these sections and datasets.