Wilmsen Saskia, Gottlieb Robin, Junker Robert R, Lunau Klaus
Department Biology Institute of Sensory Ecology Heinrich-Heine-University Düsseldorf Germany.
Department Biology Institute of Sensory Ecology Heinrich-Heine-University Düsseldorf Germany; Department of Ecology and Evolution University of Salzburg Salzburg Austria.
Ecol Evol. 2017 Feb 1;7(5):1384-1393. doi: 10.1002/ece3.2768. eCollection 2017 Mar.
Flower visits are complex encounters, in which animals are attracted by floral signals, guided toward the site of the first physical contact with a flower, land, and finally take up floral rewards. At close range, signals of stamens and pollen play an important role to facilitate flower handling in bees, yet the pollen stimuli eliciting behavioral responses are poorly known. In this study, we test the response of flower-naive bumblebees () toward single and multimodal pollen stimuli as compared to natural dandelion pollen. As artificial pollen stimuli, we used the yellow flavonoid pigment quercetin, the scent compound eugenol, the amino acid proline, the monosaccharide glucose, and the texture of pollen-grain-sized glass pellets as a tactile stimulus. Three test stimuli, dandelion pollen, one out of various uni- and multimodal stimulus combinations, and a solvent control were presented simultaneously to individual bumblebees, whose response was recorded. The results indicate that bumblebees respond in an irreversible sequence of behavioral reactions. Bumblebees approached the visual stimulus quercetin as often as natural dandelion pollen. An additional olfactory stimulus resulted in slightly more frequent landings. The multimodal stimulus combinations including visual, olfactory, gustatory, and tactile stimuli elicited approaches, antennal contacts, and landings as often as natural pollen. Subsequent reactions like proboscis extension, mandible biting, and buzzing were more often but not regularly observed at dandelion pollen. Our study shows that visual signals of pollen are sufficient to trigger initial responses of bumblebees, whereas multimodal pollen stimuli elicit full behavioral response as compared to natural pollen. Our results suggest a major role of pollen cues for the attraction of bees toward flowers and also explain, why many floral guides mimic the visual signals of pollen and anthers, that is, the yellow and UV-absorbing color, to direct bumblebees toward the site where they access the floral rewards.
访花是复杂的行为，在此过程中动物被花朵信号吸引，被引导至首次与花朵进行身体接触的位置，着陆并最终获取花蜜。在近距离时，雄蕊和花粉的信号在促进蜜蜂处理花朵方面起着重要作用，但引发行为反应的花粉刺激却鲜为人知。在本研究中，我们测试了从未接触过花朵的熊蜂对单一和多模式花粉刺激的反应，并与天然蒲公英花粉进行比较。作为人工花粉刺激物，我们使用了黄色类黄酮色素槲皮素、气味化合物丁香酚、氨基酸脯氨酸、单糖葡萄糖以及花粉粒大小的玻璃珠的质地作为触觉刺激物。将三种测试刺激物——蒲公英花粉、各种单模式和多模式刺激组合中的一种以及溶剂对照——同时呈现给单个熊蜂，并记录其反应。结果表明，熊蜂会以不可逆的行为反应序列做出反应。熊蜂接近视觉刺激物槲皮素的频率与天然蒲公英花粉一样高。额外的嗅觉刺激会导致着陆频率略有增加。包括视觉、嗅觉、味觉和触觉刺激在内的多模式刺激组合引发接近、触角接触和着陆的频率与天然花粉一样高。随后的反应，如喙伸展、下颌咬噬和嗡嗡声，在蒲公英花粉上更常出现，但并非总是如此。我们的研究表明，花粉的视觉信号足以触发熊蜂的初始反应，而与天然花粉相比，多模式花粉刺激会引发完整的行为反应。我们的结果表明花粉线索在吸引蜜蜂飞向花朵方面起着重要作用，也解释了为什么许多花朵引导物会模仿花粉和花药的视觉信号，即黄色和吸收紫外线的颜色，以引导熊蜂前往获取花蜜的位置。
