Wild and managed bees are essential for global food security and the maintenance of biodiversity. At present, the conservation of wild bees is hampered by a huge shortfall in knowledge about the trends and status of individual species mainly due to their large diversity and variation in life histories. In contrast, the managed Western honey bee Apis mellifera is one of the best studied and monitored insects in existence. Since similar drivers may be relevant for the decline of wild bees and losses of managed honey bees, this raises the possibility that monitoring of honey bees may help to detect threatened regions for wild bees, thereby fostering urgently required conservation measures. However, this possible relationship has not yet been explicitly tested for. Moreover, research currently focused on honey bees as a model species may yield important insights into wild insect susceptibility to stressors and vice versa. Here we use the bees of Europe as a model to show that managed honey bees are not suitable surrogates for detecting declines in wild bees. A direct comparison of the response of wild bees and honey bees to the same threats (nutritional deficiencies, parasites and pathogens, pesticides, and a changing climate) shows that, whilst some of their responses may be similar at the individual level, when considered at the reproductive level (individuals versus colonies), many of their responses diverge. These results reinforce the need for basic research into wild bee biology, the need for national monitoring schemes for wild bee populations, and the call for conservation actions tailored to the individual ecologies of wild bee species.wild bees / indicator species / species specific / sociality / populations

Wild bees are facing a global decline mostly induced by numerous human factors for the last decades. In parallel, public interest for their conservation increased considerably, namely through numerous scientific studies relayed in the media. In spite of this broad interest, a lack of knowledge and understanding of the subject is blatant and reveals a gap between awareness and understanding. While their decline is extensively studied, information on conservation measures is often scattered in the literature. We are now beyond the precautionary principle and experts are calling for effective actions to promote wild bee diversity and the enhancement of environment quality. In this review, we draw a general and up-to-date assessment of the conservation methods, as well as their efficiency and the current projects that try to fill the gaps and optimize the conservation measures. Targeting bees, we focused our attention on (i) the protection and restoration of wild bee habitats, (ii) the conservation measures in anthropogenic habitats, (iii) the implementation of human made tools, (iv) how to deal with invasive alien species, and finally (v) how to communicate efficiently and accurately. This review can be considered as a needed catalyst to implement concrete and qualitative conversation actions for bees.

It is now well established that invasive plants may induce drifts in the quantity and/or quality of floral resources. They are then often pointed out as a potential driver of bee decline. However, their impact on bee population remains quite unclear and still controversial, as bee responses are highly variable among species. Here, we compared the amino acid composition of pollen from three native and two invasive plant species included in diets of common pollinators in NW Europe. Moreover, the nutritional intake (i.e., pollen and amino acid intakes) of Bombus terrestris colonies and the pollen foraging behaviour of workers (i.e., visiting rate, number of foraging trips, weight of pollen loads) were considered. We found significant differences in pollen nutrients among the studied species according to the plant invasive behaviour. We also found significant differences in pollen foraging behaviour according to the plant species, from few to several foraging trips carrying small or large pollen loads. Such behavioural differences directly impacted the pollen intake but depended more likely on plant morphology rather than on plant invasive behaviour. These results suggest that common generalist bumble bees might not always suffer from plant invasions, depending on their behavioural plasticity and nutritional requirements.

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