Abstract
Simple SummaryThe honeybee Apis mellifera is one of the main pollinators in agricultural ecosystems and therefore they are exposed to pesticides and the reduction of floral diversity. Cytochrome P450 monooxygenases are enzymes involved in xenobiotic detoxification used by organisms, including insects. In this study, we evaluated honeybee foraging activity and the expression profiles of several cytochromes, before and after the administration of a mixture of three of the most used herbicides in the region during the summer season. Additionally, we investigated whether colonies located in three distinct agricultural environments with different crop/wild flora proportions are affected similarly or differently by herbicide administration. We found that the expression of several cytochrome P450 genes decreased significantly in larvae after post-emergence weed control and they showed significant differences between apiaries in the case of honeybee workers. Besides, we found significant positive correlations between pollen collection and some pesticide detoxification genes. Our results support that diversity and quality of resource availability as well as the presence of herbicides affect colonies’ nutritional state and bee health. Moreover, their detoxification response shows that larvae are more harmed than adults in these agricultural ecosystems.The honeybee Apis mellifera is exposed to agricultural intensification, which leads to an improved reliance upon pesticide use and the reduction of floral diversity. In the present study, we assess the changes in the colony activity and the expression profile of genes involved in xenobiotic detoxification in larvae and adult honeybees from three apiaries located in agricultural environments that differ in their proportion of the crop/wild flora. We evaluated these variables before and after the administration of a mixture of three herbicides during the summer season. The expression of several cytochrome P450 monooxygenases decreased significantly in larvae after post-emergence weed control and showed significant differences between apiaries in the case of honeybee workers. Principal component analysis (PCA) revealed that colonies located in the plot near to a wetland area exhibited a different relative gene expression profile after herbicide application compared with the other plots. Moreover, we found significant positive correlations between pollen collection and the pesticide detoxification genes that discriminated between plots in the PCA. Our results suggest that nutrition may modify herbicide impact on honeybees and that larvae are more harmed than adults in agroecosystems, a factor that will alter the colonies’ population growth at the end of the blooming period.
Highlights
Honeybees (Apis mellifera L.) are one of the main pollinators in natural and agricultural ecosystems [1]; their populations are growing at a slower pace than the demands for pollination services [2,3]
The statistical analysis revealed that total incoming rate, pollen foragers’ incoming rate and ratio of pollen/total incoming rate were significantly lower after herbicide administration (Wilcoxon paired test, N = 24, p < 0.001, Table S2), even though the availability of floral resources was increased in the second sampling moment
Pollen foragers’ incoming rate and ratio of pollen/total incoming rate showed significant differences between plots (Figure 2), with the collection of pollen and the proportion of pollen/total incoming rate being higher in the C plot apiary (Friedman rank sum test, N = 24, p < 0.001, Table S2)
Summary
Honeybees (Apis mellifera L.) are one of the main pollinators in natural and agricultural ecosystems [1]; their populations are growing at a slower pace than the demands for pollination services [2,3]. The declines of beehives in many countries have been attributed to multiple factors, including pathogens, parasites, habitat loss and fragmentation [4,5]. In addition to these factors, bees are exposed to agrochemicals in agricultural landscapes and intensive mono-cropping systems which lead to reduced floral resources and nutrition [4,6]. Since the buffer zone itself often contains flowers that attract pollinators, an additional in-field buffer zone can be used to protect pollinators from drifting pesticides and to offer them diverse food sources [9]
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