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High rates of nectar depletion in summer grasslands indicate competitive conditions for pollinators
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  • Douglas Sponsler,
  • Christophe Dominik,
  • Carolin Biegerl,
  • Hanna Honchar,
  • Oliver Schweiger,
  • Ingolf Steffan-Dewenter
Douglas Sponsler
University of Würzburg

Corresponding Author:douglas.sponsler@uni-wuerzburg.de

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Christophe Dominik
Helmholtz Centre for Environmental Research - UFZ
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Carolin Biegerl
University of Würzburg
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Hanna Honchar
Helmholtz-Centre for Environmental Research - UFZ
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Oliver Schweiger
Helmholtz Centre for Environmental Research - UFZ
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Ingolf Steffan-Dewenter
University of Würzburg
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Abstract

Competition among pollinators for floral resources is a phenomenon of both basic and applied importance. While competition is difficult to measure directly under field conditions, it can be inferred indirectly through the measurement of floral resource depletion. In this study, we conducted a pollinator exclusion experiment to calculate nectar depletion rates in summer across 16 grassland sites in the German regions of Franconia and Saxony-Anhalt. Overall depletion rates were estimated at 95% in Franconia and 79% in Saxony-Anhalt, indicating strong nectar limitation and, by implication, competition among pollinators. Despite being ubiquitous in our study regions, honey bees were scarce at our sites at the time of nectar sampling. This demonstrates that wild pollinators alone are capable of massive nectar depletion, and the addition of managed honey bees to wild pollinator communities may intensify already competitive conditions. Nevertheless, the manifest diversity of the pollinator communities at our sites indicates that other factors, such as non-trophic constraints or temporal variation in food limitation, can mitigate competitive exclusion despite immediate conditions of acute food scarcity.
20 Oct 2023Submitted to Oikos
23 Oct 2023Submission Checks Completed
23 Oct 2023Assigned to Editor
23 Oct 2023Review(s) Completed, Editorial Evaluation Pending
11 Mar 20241st Revision Received
11 Mar 2024Submission Checks Completed
11 Mar 2024Assigned to Editor
12 Apr 2024Editorial Decision: Accept