Pollen source gathered by managed honey bees and unmanaged wild bees: implications for wild bees’ conservation in the insular ecosystems of the Tuscan Archipelago National Park.

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Abstract
Insect pollination supports biodiversity in natural and agricultural systems. However, increasing beekeeping activity raises concerns about the impacts of managed Apis mellifera on wild bees, already threatened by land-use change, agricultural intensification, pesticides, climate change, and invasive species. Understanding interspecific interactions is therefore essential to inform wild bee conservation and management strategies. This study investigated pollen resource use and trophic niche overlap between managed honey bees and wild bee communities on Capraia, Elba, and Giglio islands, within the Tuscan Archipelago National Park, through morphological and molecular pollen analyses. Pollen-use overlap with managed honey bees was recorded in 58.7% of the interactions with wild bee species, with an overall medium–low niche overlap (α ≤ 0.59), while only 16.7% of interactions showed high overlap. Significant differences in pollen composition were detected between honey bees and the genera Andrena, Bombus, Ceratina, Colletes, Heriades, Megachile and Seladonia. These patterns may suggest limited trophic competition between honey bees and wild bees, but low niche overlap does not necessarily imply its absence. The negative relationship observed between honey bee density and pollen overlap suggests that wild bees may increasingly rely on alternative pollen sources under higher honey bee densities, indicating trophic repartition as a potential response to competitive pressure. Since National Parks play a key role in conserving pollinators, precautionary approaches towards a low-intensity beekeeping management and further research on the mechanisms underlying these interactions that may potentially threat the survival of wild bee communities are essential for their conservation.

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