Farbpräferenzen stachelloser Bienen - Charakteristika einer außergewöhnlichen visuellen Ökologie
Zusammenfassung der Projektergebnisse
Social bees are known as important pollinators in their respective habitats, however, concerning many aspects of plant-pollinator interactions single species such as Apis mellifera or Bombus terrestris are investigated and general conclusions are drawn for social bees. Stingless bees are by far the most speciose and diverse tribe of social bees, with more than 500 described species. In comparison to the domesticated Western honey bee, stingless bees produce less honey, but they have proven to be effective pollinators for many crops, including unsuitable crops for honey bees like buzz-pollinated plants in greenhouses. In this project, we investigated colour preferences of stingless bees to analyse whether all social bees prefer similar colours or if their choice behaviour is divergent. Previous studies investigated the close association between floral colour reflectance and bee colour perception. Based on these information, we assumed that colour perception in bees should be similar in means of preferences for specific colour traits of flowers, like bluish hues and high values of saturation because both parameters can be associated with higher nectar rewards. First, innate preferences of the Australian native stingless bee Tetragonula carbonaria were analysed by offering small groups of foragers a choice between ten differently coloured broadband stimuli under laboratory conditions. The workers chose bluish colours more often and were influenced by higher green contrast and an interaction between green contrast and saturation. In an additional reciprocal experiment with T. carbonaria, experienced workers were individually trained to forage in an arena. They were given the choice between stimuli of the same blue colour hue that either differed in saturation or brightness. Neither brightness nor saturation influenced their colour choices. The same experiment was conducted with A. mellifera that chose high saturated colours significantly more frequent, while showing no preferences based on brightness. Two experiments concerning colour preferences of stingless bees were executed in Brazil. In the first experiment, workers of two Melipona species had to make quadruple choices of different colour hues or of the same colour hue with different variations of the colour parameters brightness and saturation. M. quadrifasciata preferred yellow, whereas M. mondury preferred UV-reflecting blue. In the second experiment, M. bicolor and Partamona helleri were individually trained and had to make 57 dual choices, in which colours with differing hues or differing values of brightness and saturation were offered. While M. bicolor generalized all colours, workers of P. helleri chose bluish colour hues significantly more frequent and also preferred high values of saturation. The results obtained for P. helleri refer to known preferences of honey bees and bumble bees, while the results for the other tested stingless bee species do not resemble those of other social bees. One reason for the divergence of colour preferences between most stingless bees and honey bees could be the communication via olfactory signals by stingless bees, so called scent marks. Stingless bees are known to use scent marks for the recruitment of nestmates. The last experiment of this project explored the importance of deposited scent marks, colour and location on the bees’ selection of food sources. M. subnitida and Plebeia flavocincta were trained to forage on mass feeders in Brazil, whereas honey bees were trained the same way in Germany. All three species significantly preferred the feeder that was previously scent marked by conspecifics. When given the choice between a blue and a yellow feeder honey bees chose the blue feeder with strong fidelity, while the stingless bees preferred the feeder they were trained to in most cases. M. subnitida additionally preferred feeders with closer proximity to their hive. In total, the results of this project suggest that colour preferences in social bees have some similarities, but overall colour seems to be less important to stingless bees. The recruitment via scent marks or adaptations to their respective habitat could be responsible for the differences of colour preferences in social bees. Ambient light conditions as well as physiological characteristics, like the size of the bees’ eyes that correlate with body size which is smaller in many stingless bees compared to honey bees, could be reasons for poorer colour vision or a weaker dependence on visual cues.
Projektbezogene Publikationen (Auswahl)
- (2016) Colour is more than hue: preferences for compiled colour traits in the stingless bees Melipona mondury and M. quadrifasciata. Journal of Comparative Physiology A 202: 615-627
Koethe S, Bossems J, Dyer AG and Lunau K
(Siehe online unter https://doi.org/10.1007/s00359-016-1115-y) - (2016) Innate colour preferences of the Australian native stingless bee Tetragonula carbonaria Sm. Journal of Comparative Physiology A 202: 603-613
Dyer AG, Boyd-Gerny S, Shrestha M, Lunau K, Garcia JE, Koethe S and Wong BBM
(Siehe online unter https://doi.org/10.1007/s00359-016-1101-4) - (2018) Spectral purity, intensity and dominant wavelength: Disparate colour preferences of two Brazilian stingless bee species. PLoS ONE 13(9): e0204663
Koethe S, Banysch S, Alves-dos-Santos I and Lunau K
(Siehe online unter https://doi.org/10.1371/journal.pone.0204663) - Dissertation “Impact of colour preferences on the foraging behaviour of tropical stingless bees”
Sebastian Köthe
