Global taxonomic, functional, and phylogenetic diversity of bees in apple orchards

An essential prerequisite to safeguard pollinator species is characterisation of the multifaceted diversity of crop pollinators and identification of the drivers of pollinator community changes across biogeographical gradients. The extent to which intensive agriculture is associated with the homogenisation of biological communities at large spatial scales remains poorly understood. In this study, we investigated diversity drivers for 644 bee species/morphospecies in 177 commercial apple orchards across 33 countries and four global biogeographical biomes. Our findings reveal significant taxonomic dissimilarity among biogeographical zones. Interestingly, despite this dissimilarity, species from different zones share similar higher-level phylogenetic groups and similar ecological and behavioural traits (i.e. functional traits), likely due to habitat filtering caused by perennial monoculture systems managed intensively for crop production. Honey bee species dominated orchard communities, while other managed/manageable and wild species were collected in lower numbers. Moreover, the presence of herbaceous, uncultivated open areas and organic management practices were associated with increased wild bee diversity. Overall, our study sheds light on the importance of large-scale analyses contributing to the emerging fields of functional and phylogenetic diversity, which can be related to ecosystem function to promote biodiversity as a key asset in agroecosystems in the face of global change pressures.

Methods
During the apple blooming season in 2019 (except Bhutan in 2020), we surveyed 177 commercial apple orchards in 33 countries covering six continents following a strict and standardised protocol combining netting and pan trapping (3 days). This datasets represents the all community matrix used in the article "Global taxonomic, functional, and phylogenetic diversity of bees in apple orchards.

Each site was sampled for three days (consecutive if weather permitting) during the peak blooming period. Netting collection incorporated surveying all bee specimens seen directly visiting the blossoms over two 90 min sessions (morning and afternoon) per day, while walking through orchard rows. Passive sampling consisted of deploying of painted pan traps at 9 h00 each day, in three trios (fluorescent yellow, fluorescent blue, and white) on cleared ground. The pan traps were filled with soapy water and were collected at 4 h00. All
pan traps were painted at the Agroecology Lab (ULB, Belgium) then dispatched to each collaborator to ensure comparability of the results.

In the present study, we only considered bee species as they are the
main pollinators of apple trees. Each bee specimen was identified by regional experts either to species or morphospecies level (except for the Bombus terrestris agg.
complex) depending on the available knowledge and identification tools in the specific country; this sometimes required sending of material for expert identification. We aggregated together the records of Andrena scotica and A. carantonica (named A. scotica in the dataset) due to taxonomic uncertainties. Morphospecies designations were specific to each country.