title: Amino acid and carbohydrate tradeoffs by honey bee nectar foragers and their implications for plant-pollinator interactions.
abstract: Honey bees are important pollinators, requiring floral pollen and nectar for nutrition. Nectar is rich in sugars, but contains additional nutrients, including amino acids (AAs). We tested the preferences of free-flying foragers between 20 AAs at 0.1% w/w in sucrose solutions in an artificial meadow. We found consistent preferences amongst AAs, with essential AAs preferred over nonessential AAs. The preference of foragers correlated negatively with AA induced deviations in pH values, as compared to the control. Next, we quantified tradeoffs between attractive and deterrent AAs at the expense of carbohydrates in nectar. Bees were attracted by phenylalanine, willing to give up 84units sucrose for 1unit AA. They were deterred by glycine, and adding 100 or more units of sucrose could resolve to offset 1unit AA. In addition, we tested physiological effects of AA nutrition on forager homing performance. In a no-choice context, caged bees showed indifference to 0.1% proline, leucine, glycine or phenylalanine in sucrose solutions. Furthermore, flight tests gave no indication that AA nutrition affected flight capacity directly. In contrast, low carbohydrate nutrition reduced the performance of bees, with important methodological implications for homing studies that evaluate the effect of substances that may affect imbibition of sugar solution. In conclusion, low AA concentrations in nectar relative to pollen suggest a limited role in bee nutrition. Most of the 20 AAs evoked a neutral to a mild deterrent response in bees, thus it seems unlikely that bees respond to AAs in nectar as a cue to assess nutritional quality. Nonetheless, free choice behavior of foraging bees is influenced, for instance by phenylalanine and glycine. Thus, AAs in nectar may affect plant-pollinator interactions and thereby exhibit a selective pressure on the flora in the honey bee habitat.
authors: B. Triwaks Bee Research Center, Department of Entomology, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel. Electronic address: harmenhendriksma@gmail.com.
authors: Harmen P
authors: HP
authors: Hendriksma
authors: B. Triwaks Bee Research Center, Department of Entomology, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
authors: Karmi L
authors: KL
authors: Oxman
authors: B. Triwaks Bee Research Center, Department of Entomology, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
authors: Sharoni
authors: S
authors: Shafir
mesh_terms: D000596:Amino Acids / Q000502:physiology*; D000818:Animals; D001516:Bees / Q000502:physiology*; D004040:Dietary Carbohydrates; D005426:Flight, Animal; D005518:Food Preferences; D006702:Homing Behavior; D009747:Nutritional Physiological Phenomena; D057048:Plant Nectar / Q000502:physiology*; D054817:Pollination; D013395:Sucrose
chemical_list: D000596:Amino Acids; D004040:Dietary Carbohydrates; D057048:Plant Nectar; D013395:Sucrose
keywords: Equivalence point; Essential amino acids; Homing; Nutrient balance; Pollination ecology; pH deviation