Data from: Looks matter: changes in flower form affect pollination effectiveness in a sexually-deceptive orchid

Many species of the sexually-deceptive genus Ophrys are characterized by insect-like flowers. Their form has been traditionally considered to play an important role in pollinator attraction and manipulation. Yet the evolution of the floral form remains insufficiently understood. We hypothesize that pollinator-mediated selection is essential for driving floral form evolution in Ophrys, but that form components are being subjected to varying selection pressures depending on their role in mediating interactions with pollinators. By using the Eucera pollinated Ophrys leochroma as a model, our aim has been to assess whether and in what manner pollination effectiveness is altered by experimental manipulation of the flower form. Our results show that the floral form plays an essential and, so far, underestimated role in ensuring effective pollination by mechanically guiding pollinators towards the reproductive structures of the flower. Pollinators are significantly less effective in interacting with flowers having forms altered to resemble those of species pollinated by different hymenopteran genera. Further, those components used by pollinators as gripping points were found to be more effective in ensuring pollinia transfer than those with which pollinators do not directly interact. Thus, mechanically-active and –inactive components appear to be under different selection pressures. As a consequence, mechanically-active components of the flower form could reflect adaptations to the interaction with particular pollinator groups, while inactive components can vary more freely. Disentangling selection patterns between the functionally different components of flower form may provide valuable insights into the mechanisms driving the morphological diversification of sexually-deceptive pollination-systems.

性欺骗眉兰属（Ophrys）的多数物种，其花朵具有类昆虫形态特征。传统观点认为，其花部形态在吸引、操控传粉昆虫方面发挥着关键作用。然而学界对该属植物花部形态的演化机制仍知之甚少。本研究提出假说：传粉昆虫介导的选择作用是驱动眉兰属花部形态演化的核心动力，而花部各组成部分因在传粉互作中发挥的功能不同，会承受差异化的选择压力。本研究以被长须蜂属（Eucera）传粉的眉兰物种Ophrys leochroma为研究模型，旨在探究通过实验操控花部形态后，传粉效率是否发生改变，以及具体的改变方式。研究结果表明，花部形态通过机械引导传粉昆虫抵达花的生殖结构，从而保障高效传粉——这一关键且此前被学界低估的作用，现已得到证实。当花部形态被改造为与被其他膜翅目昆虫属类传粉的物种相似时，传粉昆虫与花的互动效率会显著降低。进一步研究发现，传粉昆虫用作抓握位点的花部结构，相较于传粉昆虫未直接接触的结构，更能有效保障花粉块（pollinia）的传递。由此可见，具有机械活性与无机械活性的花部结构，承受着不同的选择压力。因此，花部形态中具有机械活性的结构，可反映出其对特定传粉昆虫类群的适应性演化，而无机械活性的结构则可发生更为自由的变异。厘清花部不同功能组分间的选择模式，可为揭示性欺骗传粉系统的形态多样化驱动机制提供重要的研究视角。