[Pollinator] apple pollination study

[David Inouye]

Weekers, T., et al. (2022). "Dominance of honey bees is negatively 
associated with wild bee diversity in commercial apple orchards 
regardless of management practices." Agriculture, Ecosystems & 
Environment 323: 107697.
     Commercial apple production relies on managed honey bees (Apis 
mellifera) for pollination, and on intensive management for pest 
control. Previous studies have highlighted the potentially detrimental 
effects of intensive crop management on wild bee diversity in 
agroecosystems, potentially jeopardizing the pollination services they 
provide. However, the extent to which honey bee dominance and crop 
management interact under field-realistic conditions and drive the 
structure of wild bee assemblages has not been investigated so far. In 
this study, we measured species richness, as well as the functional and 
phylogenetic diversity of wild bee assemblages in 36 paired organic and 
non-organic apple orchards during their flowering season and along a 
geographic gradient across western Europe. Our results show a strong 
significant and negative association between honey bee dominance and all 
wild bee diversity metrics, regardless of local management. Semi-natural 
habitats had a significant and positive effect on functional diversity, 
while urbanization and crop cover around the orchards showed no effect 
on all measured diversity metrics. A greater number of species exhibited 
less common, or frequent, combinations of functional traits at sites 
with high honey bee dominance, especially larger bee species with longer 
tongues. Collectively, we show that wild bee diversity decreases with 
increasing honey bee dominance, and that this negative association is 
not buffered by alternative (i.e., organic) management practices in 
commercial apple orchards. Although organic farming can bring about 
biodiversity benefits, our study demonstrates that, in the context of 
commercial apple production, other measures are needed to enhance and 
harness biodiversity for sustainable and profitable crop production. In 
particular, a lowered reliance on honey bees and a redesign of orchards 
through configurational crop heterogeneity and/or the restoration of 
in-field semi‐natural elements are required beyond agricultural input 
substitution.


-- 
Dr. David W. Inouye
Professor Emeritus
Department of Biology
University of Maryland

Principal Investigator
Rocky Mountain Biological Laboratory