Effect of diet on incipient colony success for two long-tongued bumblebee species in the laboratory

Abstract

Bumblebees (Bombus spp.) are ecologically and economically important pollinating insects and nutritional stress is one of the most significant factors causing their decline. However, our knowledge of the nutritional requirements of bumblebees is largely limited to just a small number of species that can be easily reared in the laboratory, so there is an important need to understand the nutritional requirements of a greater range of bumblebee species. In particular, the long-tongued, pocket maker species that have been intractable to laboratory rearing, yet are often of greatest conservation concern. Here, we compare the development and success of incipient colonies in two species of pocket maker bumblebees (B. pascuorum and B. hortorum) when fed either a less diverse or more diverse pollen diet. Our results show that both diets were sufficiently good for queens of both species to rear workers, but they performed significantly better for some variables on the less diverse diet. Our findings support previous work that suggests that a less diverse diet can be as good as a highly diverse mix in some respects. We also observed significant differences between species, demonstrating why we must not rely only on one or two model species to understand the effects of nutritional stress on bumblebee communities.

Using physiology to better support wild bee conservation

“…It is now well established that the protein and lipid contents of pollens have a significant impact on bumblebee immunity, development and survival ( Vanderplanck et al, 2014 ; Roger et al, 2017 ). If pollen diversity might not provide an added value per se (as compared to higher quality monofloral pollens), it might help to mitigate the negative effect of unfavourable pollens ( Moerman et al, 2017 ; Carnell et al, 2020 ). The benefit of pollen mixing was notably demonstrated by Eckhardt et al in the pollen-generalist solitary bee Osmia cornuta ( Eckhardt et al, 2014 ).…”