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.背景与研究目的：植物与传粉者的互作塑造了花的演化。花的吸引性状与奖励性状通常已被证实会影响传粉者行为，但效率性状对访花行为的潜在影响却极少被探讨。本研究以野萝卜（Raphanus raphanistrum）的花为研究对象，测试了通常被认为是影响传粉者花粉沉积效率的性状——花药着生位置（anther position），对传粉者访花频率及单次访花时长的影响。 研究方法：我们利用两项实验的人工选择系（artificial selection lines），以拓展野萝卜花药着生位置的自然表型变异范围。其中一项实验通过人工选择培育出花药伸出度（anther exsertion）升高或降低的株系；另一项实验则通过降低花药二态性（anther dimorphism），使短雄蕊的伸出度得以提升。我们提出两项假设：其一，花药伸出度升高会通过增强视觉吸引力，提升花粉采食者（pollen foragers）的访花频次；其二，伸出花冠（corolla）之上的花药会干扰花蜜采食者（nectar foragers）的访花行为，并延长单次访花时长。 主要研究结果：在花药伸出度选择实验中，短雄蕊与长雄蕊的伸出度同时升高，均会导致单株植株的蝇类访花次数增加；而在花药二态性实验中，短雄蕊伸出度升高则会提升蜂类的访花次数。与假设相悖的是，随着长雄蕊伸出度的升高，花蜜采食者的单次访花时长显著缩短。 结论与综合分析：此前，花药着生位置一直被视为提升花粉摄取与沉积效率的效率性状。本研究表明，野萝卜的花药着生位置在吸引花粉采食者方面同样具有生态学意义。本研究揭示了花药着生位置除效率功能外的另一重适应性角色，并强调了花部性状在植物-传粉者互作中的多重生态功能。