Data from: An experimental evaluation of traits that influence the sexual behaviour of pollinators in sexually deceptive orchids

Pollination by sexual deception of male insects is perhaps one of the most remarkable cases of mimicry in the plant kingdom. However, understanding the influence of floral traits on pollinator behaviour in sexually deceptive orchids is challenging, due to the risk of confounding changes in floral odour when manipulating morphology. Here, we investigated the floral traits influencing the sexual response of male Zaspilothynnus nigripes (Tiphiidae) wasps, a pollinator of two distantly related sexually deceptive orchids with contrasting floral architecture, Caladenia pectinata and Drakaea livida. In D. livida the chemical sexual attractant is emitted from the labellum, while in C. pectinata it is produced from the distal sepal tips, allowing manipulative experiments. When controlling for visual cues there was no difference in long distance attraction, though the floral odour of D. livida induced copulation more frequently than that of C. pectinata. The role of colour in pollinator sexual attraction was equivocal, indicating that colour may not be a strong constraint on the initial evolution of sexual deception. The frequency of wasp visitors landing on C. pectinata decreased when the amount of floral odour was reduced, but attempted copulation rates were enhanced when the source of floral odour was associated with the labellum. These latter variables may represent axes of selection that operate across many sexually deceptive species. Nonetheless, the observed variation in floral traits suggests flexibility in how sexual deception can be achieved.

雄性昆虫的性欺骗传粉，或许是植物界中最引人注目的拟态案例之一。然而，在操控花部形态时，花香会产生混杂性变化，这使得探究性欺骗兰科植物的花部性状对传粉者行为的影响极具挑战。本研究针对两种亲缘关系疏远、花部结构迥异的性欺骗兰科植物——梳状蜘蛛兰（Caladenia pectinata）与淡色锤兰（Drakaea livida）的传粉者黑刺土蜂（Zaspilothynnus nigripes，土蜂科Tiphiidae）雄性个体的性反应相关花部性状展开了调查。淡色锤兰的化学性引诱物质由唇瓣释放，而梳状蜘蛛兰的该物质则产自萼片远端尖端，这为控制性实验提供了可行条件。在控制视觉信号的前提下，两种兰科植物的长距离引诱能力并无显著差异，但淡色锤兰的花香诱导交配的频率显著高于梳状蜘蛛兰。颜色在传粉者性吸引中的作用尚无定论，这表明颜色或许并非性欺骗传粉初始演化的强约束因子。当花香释放量降低时，停靠在梳状蜘蛛兰上的土蜂访花频率有所下降，但当花香来源与唇瓣关联时，土蜂的尝试交配率反而有所提升。上述变量或许代表了跨多个性欺骗兰科物种起作用的选择压力轴。尽管如此，观测到的花部性状变异表明，性欺骗传粉的实现路径具有灵活性。