Drought reduces floral resources for pollinators

Abstract

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.

Local adaptation mediates floral responses to water limitation in an annual wildflower

“…Pollinators often prefer plants with larger floral displays (number of flowers), or flower size (signals to pollinators; Eckhart, 1991;Thompson, 2001;Goulson, 2010;Sletvold et al, 2017). However, decreased water availability is often associated with smaller floral display or flower size (Carroll et al, 2001;Opedal et al, 2016;Gallagher and Campbell, 2017;Descamps et al, 2018;Phillips et al, 2018). Decreased water availability is also often associated with lower volumes of nectar produced (a pollinator reward; Carroll et al, 2001;Halpern et al, 2010;Waser and Price, 2016;Gallagher and Campbell, 2017;Descamps et al, 2018).…”

Quantifying the relative predation pressure on bumblebee nests by the European badger (Meles meles) using artificial nests

“…The hotter summers predicted for the UK under future climate change scenarios (Committee on Climate Change, ) could lead to an increase in insect predation. Such predation would increase stress to bumblebee populations at a time when food availability is already compromised from drought‐induced reductions in floral diversity, floral abundance, and nectar production (Phillips et al, ). During the current study, only one transect block did not receive any nights of rainfall, while the remaining transects experienced two or three nights of rainfall.…”

Diversity matters: Effects of density compensation in pollination service during rainfall shift

“…These affect crop pollination by disrupting ovary development, increasing pollen grain sterility, and decreasing nectar volume, flower attractiveness, and seed set percentage (Alqudah, Samarah, & Mullen, ). Rainfall decline has also been shown to shift the phenology of forests (Peñuelas et al, ) and floral abundances (Phillips et al, ; Thomson, ).…”

“…Any sudden shift in climatic zones can thus create a drastic shift in pollinator community and plant–pollinator interaction across the globe (Hegland, Nielsen, Lázaro, Bjerknes, & Totland, ). Additionally, the rainfall decline can also indirectly impact the pollinator populations by affecting the availability of floral resources (Phillips et al, ). However, different pollinator species can respond to resource fluctuations differently, some being more sensitive than others.…”