Drought reduces floral resources for pollinators
Wiley Open Access
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Currently under an indefinite embargo pending publication by Wiley Open Access. No embargo required on publication.
Climate change is predicted to result in increased occurrence and intensity of drought in many regions worldwide. By increasing plant physiological stress, drought is likely to affect the floral resources (flowers, nectar and pollen) that are available to pollinators. However, little is known about impacts of drought at the community level, nor whether plant community functional composition influences these impacts. To address these knowledge gaps, we investigated the impacts of drought on floral resources in calcareous grassland. Drought was simulated using rain shelters and the impacts were explored at multiple scales and on four different experimental plant communities varying in functional trait composition. First, we investigated the effects of drought on nectar production of three common wildflower species (Lathyrus pratensis, Onobrychis viciifolia and Prunella vulgaris). In the drought treatment, L. pratensis and P. vulgaris had a lower proportion of flowers containing nectar and O. viciifolia had fewer flowers per raceme. Second, we measured the effects of drought on the diversity and abundance of floral resources across plant communities. Drought reduced the abundance of floral units for all plant communities, irrespective of functional composition, and reduced floral species richness for two of the communities. Functional diversity did not confer greater resistance to drought in terms of maintaining floral resources, probably because the effects of drought were ubiquitous across component plant communities. The findings indicate that drought has a substantial impact on the availability of floral resources in calcareous grassland, which will have consequences for pollinator behaviour and populations.
We would like to thank Nigel Follett for use of the site, and Victoria Mallott, Rachel McDonald and Joanna Savage for assistance with fieldwork. BP would like to thank The Access & Achievement Foundation and the Haberdashers’ Educational Foundation for personal financial support. An earlier draft was greatly improved by comments from two anonymous reviewers. This study was part of the Wessex Biodiversity and Ecosystem Service Sustainability (BESS) project, funded under the BESS programme, and supported by the Natural Environment Research Council (Wessex BESS, ref. NE/J014680/1).
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