Plants other than animal-pollinated herbs provide wild bees with vital nutrients

Abstract

Adult pollinators that forage primarily for energy have traditionally guided our understanding of plant–pollinator interactions, leading to assumptions about the importance of different plants to pollinators. Consequently, pollinator conservation strategies potentially overlook plants that balance juvenile diets. I studied a representative bee, Osmia bicornis, to explore the contributions of various plants to the nutritional quality of a pollinator diet. Using ecological stoichiometry and micronutrient ecology, I investigated the proportions of vital body-building chemical elements (C, N, P, S, K, Na, Ca, Mg, Fe, Zn, Mn and Cu; henceforth “nutrients”) in larval pollen loads. I considered botanical origin, location and sexual dimorphism in the nutritional niche as factors potentially influencing nutrient proportions in larval diets. Redundancy analysis indicated that the main factor determining nutrient proportion was pollen botanical origin, which accounted for 70.17% of the variation; location contributed 20.21%, and larval sex contributed 8.43%. Among the 30 taxa composing pollen loads, the main determinants of nutrient content were oak, maple, chestnut, the cabbage family, buttercup, and grasses. Trees and wind-pollinated plants provided important nutrients. Oak and maple were the main contributors of nutrients essential for growth and body development (N, P, S, Cu, and Zn). Grasses and buttercups were the main contributors of Na, which is vital for bees. Complex habitat management schemes extending beyond traditional seed mixes are essential for pollinator conservation, as non-obvious plant species provide important nutrients. Trees and wind-pollinated plants should be included in pollinator conservation efforts to create a complex nutritional landscape enabling balanced diets.

Keywords

• Agri-environment scheme
• Diet
• Weed
• Nutrition
• Wildflowers
• Resource