NECTAR PRODUCTION, COMPOSITION, ENERGETICS AND POLLINATOR ATTRACTIVENESS IN SPRING FLOWERS OF WESTERN NEW YORK

Abstract

High Performance Liquid Chromatography (HPLC) was used to determine specific sugar ratios (fructose, glucose and sucrose) in nectars of nine families of flowering plants. All nectars contained all three sugars with the exception of that of Asclepias. Asclepias nectar was nearly a pure sucrose solution. Sucrose/hexose ratio was correlated with flower morphology, with tubular flowers having more sucrose and open flowers having more hexose. Open flowers contained nectar whose concentration was more affected by relative humidity than tubular flowers. Available nectar in unbagged flowers was found in volumes of 0.1 to 5 μl (17.5 to 68.2% sugar). Total sugar available per blossom amounted to 0.07 to 3.54 mg. We note that care must be taken in converting % concentration to mg sugar. Energetic yield was not as variable as the other measures and ranged from 0.72 to 3.58 cal/μl. Total daily nectar production was measured in five families and 24‐hr sugar production varied from 0.64 to 5.52 mg per flower. Insect nectar feeders frequently searched many blossoms with little or no reward, but were rewarded sufficiently at rare “lucky hit” blossoms which contained relatively large nectar rewards. Insect pollinators did not seek nectars of specific sucrose‐hexose ratios, but instead took nectar where caloric reward and accessibility made it most profitable.