Evolution of reproductive strategies in the sexually deceptive orchid Ophrys sphegodes:: How does flower-specific variation of odor signals influence reproductive success?
Evolution of reproductive strategies in the sexually deceptive orchid Ophrys sphegodes:: How does flower-specific variation of odor signals influence reproductive success?
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DOI：
10.1111/j.0014-3820.2000.tb01243.x
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发表时间：
2000-12-01
期刊：
影响因子：
3.3
通讯作者：
Francke, W
中科院分区：
文献类型：
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作者：
Ayasse, M;Schiestl, FP;Francke, W
兰花Ophrys sphegodes Miller是由性兴奋的雄性独居蜜蜂Andrena nigroaenea授粉的，它们被视觉线索和挥发性的半化学物质吸引到花朵上。在O. sphegodes中，传粉者的来访是罕见的。由于授粉频率较低，人们会期望策略的进化会增加雄性在同一株植物上访问多朵花的机会；这将增加植物上授粉事件的数量，从而增加产生的种子数量。采用气相色谱-质谱（GC-MS）分析方法，鉴定出了百余种化合物；通过气相色谱-触角电图检测（GC-EAD），发现24种化合物在男性嗅觉受体中具有生物活性。气相色谱（GC）分析表明，与非活性化合物相比，生物活性化合物的气味花束的种内变化较小。这可以解释为对吸引传粉者的通信信号有较高的选择压力。此外，我们还发现同一花序内不同茎位花的GC-EAD活性酯类和醛类以及不同居群植物的正构烷烃和正构烷烃具有特征性差异。在我们的行为现场测试中，我们发现雄性蜜蜂在交配过程中学会了单个花束的气味，并在随后的相遇中识别它们。因此，蜜蜂避免尝试与它们以前访问过的花朵交配，但不会避免不同或同一植物的其他花朵。通过改变不同茎位花中饱和酯类和醛类的相对比例，我们证明了植物可能利用传粉者的学习能力来影响访花行为。67%的雄蜂在拜访过同一花序上的一朵花后，会再次拜访同一花序上的第二朵花。然而，沉积在传粉媒介上的花粉完成其弯曲运动所需的时间（这是授粉发生所必需的），阻止了雌雄同体，并增加了异花受精的可能性。植物间高度的气味差异进一步促进了异花受精。这种变异最大限度地减少了对花朵的学习回避，并增加了给定传粉者访问一个种群中几种或多种不同植物的可能性。
The orchid Ophrys sphegodes Miller is pollinated by sexually excited males of the solitary bee Andrena nigroaenea, which are lured to the flowers by visual cues and volatile semiochemicals. In O. sphegodes, visits by pollinators are rare. Because of this low frequency of pollination, one would expect the evolution of strategies that increase the chance that males will visit more than one flower on the same plant; this would increase the number of pollination events on a plant and therefore the number of seeds produced. Using gas chromatography-mass spectrometry (GC-MS) analyses, we identified more than 100 compounds in the odor bouquets of labellum extracts from O. sphegodes; 24 compounds were found to be biologically active in male olfactory receptors based on gas chromatography with electroantennographic detection (GC-EAD). Gas chromatography (GC) analyses of odors from individual flowers showed less intraspecific variation in the odor bouquets of the biologically active compounds as compared to nonactive compounds. This can be explained by a higher selective pressure on the pollinator-attracting communication signal. Furthermore, we found a characteristic variation in the GC-EAD active esters and aldehydes among flowers of different stem positions within an inflorescence and in the n-alkanes and n-alkenes among plants from different populations. In our behavioral field tests, we showed that male bees learn the odor bouquets of individual flowers during mating attempts and recognize them in later encounters. Bees thereby avoid trying to mate with flowers they have visited previously, but do not avoid other flowers either of a different or the same plant. By varying the relative proportions of saturated esters and aldehydes between flowers of different stem positions, we demonstrated that a plant may take advantage of the learning abilities of the pollinators and influence flower visitation behavior. Sixty-seven percent of the males that visited one flower in an inflorescence returned to visit a second flower of the same inflorescence. However, geitonogamy is prevented and the likelihood of cross-fertilization is enhanced by the time required for the pollinium deposited on the pollinator to complete its bending movement, which is necessary for pollination to occur. Cross-fertilization is furthermore enhanced by the high degree of odor variation between plants. This variation minimizes learned avoidance of the flowers and increases the likelihood that a given pollinator would visit several to many different plants within a population.