DOI: 10.5061/dryad.rfj6q57ct
title: Database from: Managed honey bees decrease pollination limitation in self-compatible but not in self-incompatible crops

description: Modern agriculture is becoming increasingly pollinator-dependent. However,
 the global stock of domesticated honey bees is growing at a slower rate
 than its demand while wild bees are declining worldwide. This uneven
 scenario of high pollinator demand and low pollinator availability can
 translate into increasing pollination limitation, reducing the yield of
 pollinator-dependent crops. However, overall assessments of crop
 pollination limitation and the factors determining its magnitude are
 missing. We assembled the first global database of pollination limitation
 in pollinator-dependent crops, encompassing 107 metadata comparing the
 quantity/quality of fruits/seeds produced by pollen supplemented vs
 naturally pollinated flowers. This database, based on 52 published
 studies, cover 30 crops in 52 crop systems. We conducted a meta-analysis
 comparing crop yield in pollen-supplemented vs. open-pollinated flowers.
 We assessed the overall magnitude of pollination limitation and whether
 this magnitude was influenced by (a) the presence/absence of managed honey
 bees, (b) crop compatibility system (i.e.,
 self-compatible/self-incompatible), and (c) the interaction between these
 two factors. 
description: Following the protocols and
 good practices stated by Nakagawa et al.  2017, we conducted a systematic literature search of
 published studies in SCOPUS, the largest abstract and citation
 multidisciplinary database of peer-reviewed literature, covering
 publications from 1900 to July 2021. We searched for studies reporting at
 least one estimate of crop yield (e.g., seed- and/or fruit-set, individual
 seed or fruit weight, fruit or seed production per plant or area unit)
 after natural (open) pollination and pollen supplementation (i.e., open
 flowers manually supplemented with outcross pollen) treatments in
 pollinator-dependent crops. A pollinator-dependent crop was defined as any
 crop that exhibits at least some yield reduction when pollinators are
 excluded.
  For a study to be
 included in the meta-analysis, it had to report the mean value, some
 measure of dispersion that could be ultimately transformed to standard
 deviation, and sample size for any of the above-mentioned measures of crop
 yield (“yield” hereafter) under both natural and supplemental pollination
 treatments in a pollinator-dependent crop. We only selected studies in
 which pollen supplementation was performed by adding outcross pollen
 manually or mechanically, at least once during flower lifespan, to the
 stigmas of otherwise open-pollinated flowers. For those studies reporting
 this information in figures, we extracted the data using
 WebPlotDigitalizer, an open web-based tool that extracts statistics from
 plots (https://automeris.io/WebPlotDigitizer/). For each selected study, we also gathered information regarding (i) the presence or absence of managed honey bees in the study crop, and (ii) crop compatibility system (i.e., SC or SI) (see Table S1 in Supporting Information). Studies that did not provide information regarding the presence/absence of managed honey bees were only considered for the evaluation of the overall pollination limitation (i.e., first question). Information regarding crop compatibility system (SC or SI) was gathered from each selected study when reported, and from Klein et al. 2007 or other literature sources when not reported in the selected study. Moreover, the crop <em>Actinia deliciosa</em> (kiwi) was included in the SI group, as it is dioecious and thus completely dependent on pollen transfer between plants for fruit production.