Reduced Water Negatively Impacts Social Bee Survival and Productivity Via Shifts in Floral Nutrition

Abstract

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 beehives 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 (Hymenoptera: Apidae) and bumble bees (Hymenoptera: Apidae). The results emphasize the importance of the nutritional effects of reduced water on bees when predicting shifts of pollination mutualisms under climate change.

A meta‐analysis of responses in floral traits and flower–visitor interactions to water deficit

“…In this context, only a few studies have explored floral scent emissions and floral color (Arista et al, 2013;Brunet & Van Etten, 2019). While the nutritional quality of nectar is essential for the reproductive success of pollen-collecting insects (Behmer, 2009;Vaudo et al, 2015), to our knowledge there are no studies exploring nectar sugar composition together with minor constituents such as amino acids and lipids, and only one study exploring pollen quality (Rankin et al, 2020), even though changes due to reduced water availability may lead to reduced pollinator reproduction and survival (Rankin et al, 2020).…”

“…With decreasing nectar volume under drought conditions, nectar sugar concentration might increase if the same amount of sugar is produced. Similarly, pollen production, quantity and quality is often resource-limited (Ashman, 1994;Obeso, 2002) and has been shown to change with abiotic factors such as soil nutrients (Lau & Stephenson, 1994;Young & Stanton, 1990) or water availability (Rankin et al, 2020). Thus, under resource limitation including water supply, pollen production may decline.…”

Pollinators and plant nurseries: how irrigation and pesticide treatment of native ornamental plants impact solitary bees

“…The lack of effect of irrigation could be due to our choice of native, drought-tolerant plants, though we had to ensure sufficient flowering even in our low irrigation treatment. Regardless, our low irrigation treatment is likely not as stressing as drought [22] or resource-limiting treatments in similar studies [12,36,67]. Rather, our low irrigation treatment mimicked a reduced watering regime, such as that which would be employed in a nursery, that avoids excessively water stressing plants.…”

“…Water availability can influence the rates of several physical and biological processes that could potentially affect the amount of a neonicotinoid present in floral resources [ 17 ]. These processes include, among others, plant transpiration [ 27 , 28 ], leaching of insecticide ingredients from soil [ 29 ], and production of flowers and floral resources by the plant [ 19 , 22 ]. Moreover, nursery plants are confined in containers, unlike plants in most other agricultural areas.…”

Gene flow in commercial alfalfa (Medicago sativa subsp. sativa L.) seed production fields: Distance is the primary but not the sole influence on adventitious presence

“…Environmental factors can affect flower density and duration, and pollinator behavior [ 20 – 22 , 36 , 40 – 43 ]. Low water availability decreases flower production which negatively impacts the resources provided by the plants to the bees [ 44 , 45 ]. According to Scorza et al [ 13 ], gene flow was correlated with distance and with weather conditions such as air temperature and rainfall.…”