Reduced water negatively impacts social bee survival and productivity via shifts in floral nutrition

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.