121 research outputs found
Ensuring access to high-quality resources reduces the impacts of heat stress on bees
Pollinators are experiencing declines globally, negatively affecting the reproduction of wild plants and crop production. Well-known drivers of these declines include climatic and nutritional stresses, such as a change of dietary resources due to the degradation of habitat quality. Understanding potential synergies between these two important drivers is needed to improve predictive models of the future effects of climate change on pollinator declines. Here, bumblebee colony bioassays were used to evaluate the interactive effects of heat stress, a reduction of dietary resource quality, and colony size. Using a total of 117 colonies, we applied a fully crossed experiment to test the effect of three dietary quality levels under three levels of heat stress with two colony sizes. Both nutritional and heat stress reduced colony development resulting in a lower investment in offspring production. Small colonies were much more sensitive to heat and nutritional stresses than large ones, possibly because a higher percentage of workers helps maintain social homeostasis. Strikingly, the effects of heat stress were far less pronounced for small colonies fed with suitable diets. Overall, our study suggests that landscape management actions that ensure access to high-quality resources could reduce the impacts of heat stress on bee decline.info:eu-repo/semantics/publishedVersio
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Monitoring bee health in European agroecosystems using wing morphology and fat bodies
Current global change substantially threatens pollinators, which directly impacts the
pollination services underpinning the stability, structure and functioning of ecosystems.
Amongst these threats, many synergistic drivers, such as habitat destruction and
fragmentation, increasing use of agrochemicals, decreasing resource diversity, as well as
climate change, are known to affect wild and managed bees. Therefore, reliable indicators
for pollinator sensitivity to such threats are needed. Biological traits, such as phenotype
(e.g. shape, size and asymmetry) and storage reserves (e.g. fat body size), are important
pollinator traits linked to reproductive success, immunity, resilience and foraging efficiency
and, therefore, could serve as valuable markers of bee health and pollination service
potential.
This data paper contains an extensive dataset of wing morphology and fat body content for
the European honeybee (Apis mellifera) and the buff-tailed bumblebee (Bombus terrestris)
sampled at 128 sites across eight European countries in landscape gradients dominated
by two major bee-pollinated crops (apple and oilseed rape), before and after focal crop
bloom and potential pesticide exposure. The dataset also includes environmental metrics
of each sampling site, namely landscape structure and pesticide use. The data offer the
opportunity to test whether variation in the phenotype and fat bodies of bees is structured
by environmental factors and drivers of global change. Overall, the dataset provides
valuable information to identify which environmental threats predominantly contribute to the
modification of these traits
Dietetic constraint of host-plant specialisation in bee evolution (Hymenoptera, Apoidea).
Asteraceae Paradox: Chemical and Mechanical Protection of Taraxacum Pollen
Excessive pollen harvesting by bees can compromise the reproductive success of plants. Plants have therefore evolved different morphological structures and floral cues to narrow the spectrum of pollen feeding visitors. Among “filtering” mechanisms, the chemical and mechanical protection of pollen might shape bee-flower interactions and restrict pollen exploitation to a specific suite of visitors such as observed in Asteraceae. Asteraceae pollen is indeed only occasionally exploited by generalist bee species but plentifully foraged by specialist ones (i.e., Asteraceae paradox). During our bioassays, we observed that micro-colonies of generalist bumblebee (Bombus terrestris L.) feeding on Taraxacum pollen (Asteraceae) reduced their pollen collection and offspring production. Bees also experienced physiological effects of possible defenses in the form of digestive damage. Overall, our results suggest the existence of an effective chemical defense in Asteraceae pollen, while the hypothesis of a mechanical defense appeared more unlikely. Pre- and post-ingestive effects of such chemical defenses (i.e., nutrient deficit or presence of toxic compounds), as well as their role in the shaping of bee-flower interactions, are discussed. Our results strongly suggest that pollen chemical traits may act as drivers of plant selection by bees and partly explain why Asteraceae pollen is rare in generalist bee diets
Invasive plants as potential food resource for native pollinators: A case study with two invasive species and a generalist bumble bee
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
Spécialisation alimentaire chez les abeilles sauvages, contrainte physiologique ou comportementale?
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