Pollinators provide a key ecosystem service vital for the survival and stability of the biosphere. Identifying factors influencing the plant-pollinator mutualism and pollinator management is necessary for maintaining a healthy ecosystem. Since healthy bee hives require substantial amounts of carbohydrates (nectar) and protein (pollen) from forage plants such as clover, we must assess how resources offered by plants change under limited water conditions in order to fully understand how drought modifies the pollination mutualism. Here we document how reduced water availability leads to decreased nectar quality and quantity and decreased protein quality of pollen. Furthermore, we provide conclusive evidence that these lower quality resources lead to decreased survival and productivity in both developing honey bees and bumble bees. The results emphasize the importance of the nutritional effects of reduced water on bees when predicting shifts of pollination mutualisms under climate change.

All plant data are for Tomcat clover (Trifolium willdenovii) grown in D-40 Deepots with UC Mix3 soil in a greenhouse with fertilized water and on one of two watering treatments: optimal and reduced (30% less). Optimal water conditions were assessed by determining how much water was required for the soil to be at field capacity.

We raised one-day old honey bee larvae, 76 microcolonies of Bombus impatiens, and four cull colonies of B. impatiens on artificial diets that represented the decreased nutritive quality of clover flowers when water was reduced by 30%. Please see main text for details. In short, for honey bees, The optimum water diet consisted of 53% (w/w) royal jelly, 6.5% sucrose, 3.1% glucose, 3.4% fructose and 34% water, while the reduced water diet was comprised of 47.6% royal jelly, 5.4% sucrose, 2.6% glucose, 2.9% fructose and 41.5% water. For bumble bees, the optimum water diet consisted of 0.250 g pollen and a sugar solution of 29.4% sucrose, 13.5% glucose, 15.9% fructose and 41.2% water, while the reduced water diet included 0.225g pollen and a sugar solution of 24.8% sucrose, 11.4% glucose, 13.4% fructose and 50.6% water. All bees were maintained in the lab and monitored daily.

This workbook contains the raw data for the paper Wilson Rankin et al (2020) Reduced water negatively impacts social bee survival and productivity via shifts in floral nutrition. Journal of Insect Science

All plant data are for Tomcat clover (Trifolium willdenovii) grown in D-40 Deepots with UC Mix3 soil in a greenhouse with fertilized water and on one of two watering treatments: optimal and reduced (30% less). Optimal water conditions were assessed by determining how much water was required for the soil to be at field capacity.