Data from: Effect of expanded variation in anther position on pollinator visitation to wild radish, Raphanus raphanistrum

Background and Aims: Plant-pollinator interactions shape the evolution of flowers. Floral attraction and reward traits have often been shown to affect pollinator behavior, but the possible effect of efficiency traits on visitation behavior has rarely been addressed. Here we tested for the effect of anther position, usually considered a trait that influences efficiency of pollen deposition on pollinators, on pollinator visitation rates and visit duration in flowers of wild radish, Raphanus raphanistrum. Methods: We used artificial selection lines from two experiments that expanded the naturally-occurring phenotypic variation in anther position. In one experiment, plant lines were selected to either increase or decrease anther exsertion. The other experiment decreased anther dimorphism, which resulted in increased short stamen exsertion. We hypothesized that increased exsertion will increase visitation of pollen foragers due to increased visual attraction. We also hypothesized that exsertion of anthers above the corolla would interfere with nectar foragers and increase time of visit per flower. Key Results: In the exsertion selection experiment, increased exsertion of both short and long stamens resulted in an increased number of fly visits per plant, and in the dimorphism experiment bee visits increased with increased short stamen exsertion. Duration of nectar feeders declined significantly with increasing long stamen exsertion, as opposed to the hypothesis. Conclusions and synthesis: Until now, anther position was considered an efficiency trait to enhance pollen uptake and deposition. We show that anther position in wild radish has an ecological significance also in attracting pollen foragers. This study suggests an additional adaptive role for anther position beyond efficiency, and highlights the multiple ecological functions of floral traits in plant-pollinator interactions.研究背景与目的：植物-传粉者互作（Plant-pollinator interactions）塑造了花的演化历程。已有大量研究表明，花的吸引与奖励性状会影响传粉者行为，但效率性状对访花行为的潜在影响却极少被关注。本研究以野萝卜（Raphanus raphanistrum）为研究对象，探讨花药位置（anther position）——通常被视为影响花粉向传粉者体内沉积效率的性状——对其访花率与单次访花时长的影响。 研究方法：我们采用两项实验中获得的人工选择品系（artificial selection lines），以扩增花药位置的自然表型变异。其中一项实验中，我们通过人工选择提高或降低了花药伸出度（anther exsertion）；另一项实验则降低了花药二态性（anther dimorphism），从而提高了短雄蕊的伸出度。我们提出两项假设：其一，花药伸出度提升会通过增强视觉吸引，增加花粉采集者（pollen foragers）的访花频次；其二，伸出花冠之上的花药会干扰花蜜采集者（nectar foragers）的取食，从而延长单次访花时长。 主要结果：在花药伸出度选择实验中，短雄蕊与长雄蕊的伸出度提升均显著增加了单株植物的蝇类访花次数；而在花药二态性实验中，短雄蕊伸出度提升则提高了蜂类的访花频次。与假设相悖的是，长雄蕊伸出度越高，花蜜采食者的单次访花时长反而显著降低。 结论与综合分析：此前，花药位置仅被视为提升花粉获取与沉积效率的效率性状。本研究表明，野萝卜的花药位置在吸引花粉采集者方面同样具有重要生态意义。本研究揭示了花药位置除效率优化之外的另一项适应性功能，并凸显了花部性状在植物-传粉者互作中的多重生态功能。