Schiestl Florian P, Ayasse Manfred
Department of Evolutionary Biology, Institute of Zoology, Althanstr. 14, 1090, Vienna, Austria.
Oecologia. 2001 Feb;126(4):531-534. doi: 10.1007/s004420000552. Epub 2001 Feb 1.
The flowers of the sexually deceptive orchid Ophrys sphegodes are pollinated by pseudocopulating males of the solitary bee Andrena nigroaenea. We investigated the changes in odor emission and reduced attractiveness that occur after pollination in these plants. We analyzed floral odor of unpollinated and pollinated flowers by gas chromatography and compared relative and absolute amounts of electrophysiologically active compounds. Headspace odor samples of O. sphegodes flowers showed a significant increase in absolute and relative amounts of all-trans-farnesyl hexanoate after pollination. Flower extracts also indicated an increase of farnesyl hexanoate after pollination. The total amount of the other physiologically active odor compounds decreased slightly. Farnesyl hexanoate is a major constituent of the Dufour's gland secretion in females of the pollinator bees, A. nigroaenea, where it functions in the lining of the brood cells. Furthermore, this compound lowers the number of copulation attempts in males. In dual-choice tests, we showed that flowers artificially scented with an amount of farnesyl hexanoate equal to the increased amount after pollination were significantly less attractive than flowers treated with solvent only. We propose that the increased production of farnesyl hexanoate in pollinated flowers is a signal to guide pollinators to unpollinated flowers of the inflorescence, which represents a new mechanism in this pollination system.
性欺骗兰花奥菲莉亚（Ophrys sphegodes）的花朵由独居蜜蜂黑带隧蜂（Andrena nigroaenea）的雄蜂通过拟交配行为进行授粉。我们研究了这些植物授粉后气味释放的变化以及吸引力降低的情况。我们通过气相色谱分析了未授粉和授粉花朵的花香，并比较了电生理活性化合物的相对含量和绝对含量。奥菲莉亚花朵的顶空气味样本显示，授粉后反式法呢基己酸酯的绝对含量和相对含量均显著增加。花朵提取物也表明授粉后法呢基己酸酯有所增加。其他生理活性气味化合物的总量略有下降。法呢基己酸酯是授粉者黑带隧蜂雌蜂杜氏腺分泌物的主要成分，在育雏细胞的内衬中起作用。此外，这种化合物会减少雄蜂的交配尝试次数。在双选测试中，我们发现用与授粉后增加量相等的法呢基己酸酯人工加香的花朵，其吸引力明显低于仅用溶剂处理的花朵。我们提出，授粉花朵中法呢基己酸酯产量的增加是一种信号，可引导传粉者前往花序中未授粉的花朵，这代表了这种授粉系统中的一种新机制。
