The adaptive significance of sensory bias in a foraging context: floral colour preferences in the bumblebee Bombus terrestris.
Innate sensory biases could play an important role in helping naive animals to find food. As inexperienced bees are known to have strong innate colour biases we investigated whether bumblebee (Bombus terrestris) colonies with stronger biases for the most rewarding flower colour (violet) foraged more successfully in their local flora. To test the adaptive significance of variation in innate colour bias, we compared the performance of colour-naive bees, from nine bumblebee colonies raised from local wild-caught queens, in a laboratory colour bias paradigm using violet (bee UV-blue) and blue (bee blue) artificial flowers. The foraging performance of the same colonies was assessed under field conditions. Colonies with a stronger innate bias for violet over blue flowers in the laboratory harvested more nectar per unit time under field conditions. In fact, the colony with the strongest bias for violet (over blue) brought in 41% more nectar than the colony with the least strong bias. As violet flowers in the local area produce more nectar than blue flowers (the next most rewarding flower colour), these data are consistent with the hypothesis that local variation in flower traits could drive selection for innate colour biases. (+info)
Nectar, not colour, may lure insects to their death.
Nectar chemistry is tailored for both attraction of mutualists and protection from exploiters.
Plants produce nectar to attract pollinators in the case of floral nectar (FN) and defenders in the case of extrafloral nectar (EFN). Whereas nectars must function in the context of plant-animal mutualisms, their chemical composition makes them also attractive for non-mutualistic, exploiting organisms: nectar robbers and nectar-infesting microorganisms. We reviewed the chemical composition of both FNs and EFNs and found that nectar composition appears tailored to fulfil these ambivalent roles. Carbohydrates and amino acids usually function in the attraction of mutualists and appear adapted to the physiological needs of the respective mutualists. Volatiles are a further group of compounds that serves in the attractive function of nectars. By contrast, secondary compounds such as alkaloids and phenols serve the protection from nectar robbers, and most nectar proteins that have been characterised to date protect FN and EFN from microbial infestation. Nectar components serve both in attraction and the protection of nectar. (+info)
CELL WALL INVERTASE 4 is required for nectar production in Arabidopsis.