Asking the pikas politely…
Pollinating bees visit flowers in order to forage for nectar and pollen, their major sources of nutrition. The plant communities that a bee interacts with vary across time and space, as different flower species dominate different habitats. One key driver of the spatial variation in plant communities is soil moisture, which creates distinct wet and dry habitats in the subalpine meadows around the Rocky Mountain Biological Laboratory (RMBL). These different flower species provide different nutritional rewards for visiting bees by producing varying amounts of sugar. Relatedly, flower species have differential responses to drought, and the very dry summer of 2018 represented a significant water challenge to flowering plants. We found that over the course of the season, wet and dry meadows contained the same amount of nectar sugar, based on the 13 species we measured. At certain time points, however, dry meadows contained more nectar owing to higher flower abundances. As expected, we also found species-specific responses to precipitation, with 3 of 4 species increasing their nectar volume and decreasing their nectar concentration once regular summer rains began, ending a period of extreme dryness. In 2 cases, D. barbeyi and M. ciliata, the volume and concentration responses counteracted each other, meaning that flowers produced the same amount of sugar during the drier and wetter periods. These responses may have implications for bee foraging because highly concentrated nectar in small volumes constitutes a poorer food source for bees, and bees are sensitive to sugar and viscosity cues.
Knowledge graph centered on Characterizing nectar content in wet and dry subal with 45 nodes and 119 connections. Top connected: Bombus, Ipomopsis, Delphinium, I. aggregata, Bombus terrestris.
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