Abstract:
Secondary metabolites produced by plants for herbivore defence are often found in floral nectar, but their
effect on the foraging behaviour and physiological performance of pollinators is largely unknown. Nicotine
is highly toxic to most herbivores, and nicotine-based insecticides may contribute to current pollinator
declines. We examined the effects of nectar nicotine on honeybee foraging choices and worker
longevity. Free-flying honeybee (Apis mellifera scutellata) workers from six colonies were given a choice
between multiple nicotine concentrations (0–1000 lM) in artificial nectar (0.15–0.63 M sucrose). The
dose-dependent deterrent effect of nicotine was stronger in lower sugar concentrations, but even the
highest nicotine concentrations did not completely repel honeybees, i.e. bees did not stop feeding on
these diets. Nicotine in nectar acts as a partial repellent, which may keep pollinators moving between
plants and enhance cross-pollination. In the second part of the study, newly emerged workers from 12
colonies were caged and fed one of four nicotine concentrations (0–300 lM) in 0.63 M sucrose for
21 days. Moderate (630 lM) nicotine concentrations had no significant detrimental effect, but high nicotine
concentrations reduced the survival of caged workers and their nectar storage in the honey comb. In
contrast, worker groups that survived poorly on sugar-only diets demonstrated increased survival on all
nicotine diets. In the absence of alternative nectar sources, honeybees tolerate naturally occurring nectar
nicotine concentrations; and low concentrations can even be beneficial to honeybees. However, high nicotine
concentrations may have a detrimental effect on colony fitness.
