A scientific note on the heavy metal contamination in the larval food of Xylocopa frontalis (Apidae) in the Brazilian savanna

Abstract

Heavy metals can naturally accumulate in the environment, but industrialization and the use of certain agrochemicals are associated with metal pollution. Despite the extensive use of pesticides in Brazilian croplands, little is known about heavy metal contamination in native bee species. Such contamination could potentially have negative consequences for both the ecosystem and the economy. In this study, we focused on Xylocopa frontalis, a facultative solitary bee that is an important pollinator of crops, especially yellow passion fruit (Passiflora edulis f. flavicarpa), which is economically significant in several regions of Brazil. We investigated the levels of essential elements and heavy metals in the larval food of X. frontalis nests from three fragments of native Brazilian savanna and three passion fruit crops. Our results indicated that samples from yellow passion fruit crops did not show higher levels of chemical contamination compared to those from Brazilian savanna areas. Our findings reveal that bee bread collected from nests of X. frontalis, a large, generalist, and facultatively social bee, contains elevated levels of Al, Zn, and Sn in both agricultural and preserved areas of the Cerrado. These results highlight the potential risk posed by environmental contamination even in areas considered relatively undisturbed and underscore the importance of monitoring multiple potentially toxic elements in wild bees to support the conservation of pollinator diversity and the continuity of their ecosystem services. Moreover, the analysis of such elements in pollen may serve as an effective bioindicator of heavy metal contamination in terrestrial ecosystems.