DOI: 10.5061/dryad.dj5f7kc
title: Data from: Impacts of honeybee density on crop yield: a meta-analysis

description: 1. There is increasing recognition that pollination deficits are limiting
 crop yields worldwide. However, management strategies for optimal insect
 pollination are still unclear for most crops. Current management focuses
 on providing high densities of honeybees, but recommended densities are
 highly variable, even within single crops and cultivars. 2. We performed
 an extensive literature search to record honeybee densities (colony
 density and/or flower visitation rates) and crop productivity (fruit set,
 seed set, fruit weight, and/or yield). Effect sizes were represented as
 the difference in crop productivity between the two most extreme levels of
 honeybee densities. 3. Out of 795 reviewed studies, only 22 analysed the
 effect of at least two levels of honeybee densities on crop productivity
 (reporting 60 resulting effect sizes in total). Moreover, few
 recommendations for crop pollination management are based on results from
 controlled experimental designs, and with comparable methodology. 4. We
 found that both colony density and visitation rates increased all the
 productivity variables. However, effects were non-linear for visitation
 rates, suggesting that there is an optimum (mean of 8-10 visits per
 flower) beyond which more honeybees are not beneficial (or even
 detrimental) for crop productivity. 5. Effect sizes for visitation rates
 were greater than that for colony densities, suggesting that visitation
 rates are a more direct measure of the pollination process. Data on the
 relation between colony density and visitation rates are lacking.
 Interestingly, effect sizes for visitation rates were greater for crops
 with separate sexes than those with hermaphroditic flowers; therefore, the
 benefits of honeybee pollination vary according to the crop biology. 6.
 Synthesis and applications. Current practices for crop pollination assume
 that more honeybees are always better for crop yield, even if the effect
 of this management on crop production still unclear. In contrast, our
 analyses suggest that there is an optimum for honeybee densities. Despite
 the importance of honeybees and pollinator-dependent crops worldwide,
 there is a lack of studies designed for finding such an optimal level of
 crop pollination. Our analyses further suggest that visitation rates could
 be used as a proxy to guide management recommendations such as colony
 density and spatial arrangement.
description: Effect sizes of 22
 studies included in the quantitative analysesThis file presents
 effect size (i.e. difference between two levels of honey bee densities, as
 measured by colony densities or flower visitation rates) on the crop
 productivity variables for one crop. Productivity variable are represented
 by fruit set, seeds per fruit, yield per plant (Kg) and fruit weight (g).
 When a study provided more than two levels of honey bee densities (which
 occurred in nine of the selected studies), we chose the two most extreme
 levels of these densities. "Study details" give the complete
 references of all the selected studies used in the
 analyses.Rollin & Garibaldi - Data
 from Impacts of honeybee density on crop yield - A meta
 analysis.xlsx