Data from: Are pollinators the agents of selection on flower colour and size in irises?

Plant-pollinator interactions are believed to play a major role in the evolution of floral traits. Flower colour and flower size are important for attracting pollinators, directly influencing reproduction, and thus expected to be under pollinator-mediated selection. Pollinator-mediated selection is also proposed to play a role in maintaining flower colour polymorphism within populations. However, pigment concentrations, and thus flower colour, are also under selective pressures independent of pollinators. We quantified phenotypic pollinator-mediated selection on flower colour and size in two colour polymorphic Iris species. Using female fitness, we estimated phenotypic selection on flower colour and size, and tested for pollinator-mediated selection by comparing selection gradients between flowers open to natural pollination and supplementary pollinated flowers. In both species, we found evidence for pollen limitation, which set the base for pollinator-mediated selection. In the colour dimorphic Iris lutescens, while pigment concentration and flower size were found to be under selection, this was independent of pollinators. For the polymorphic Iris pumila, pigment concentration is under selective pressure by pollinators, but only for one colour morph. Our results suggest that pollinators are not the main agents of selection on floral traits in these irises, as opposed to the accepted paradigm on floral evolution. This study provides an opposing example to the largely-accepted theory that pollinators are the major agent of selection on floral traits.植物-传粉者互作被认为在花部性状的演化中发挥关键作用。花的颜色与花部大小是吸引传粉者的核心性状，可直接影响繁殖成功率，因此被认为处于传粉者介导的选择压力之下。传粉者介导的选择还被提出在维持种群内花颜色多态性方面发挥作用。然而，色素浓度进而决定的花色，同样会受到不依赖于传粉者的选择压力。我们针对两种花色多态的鸢尾属（Iris）物种，量化了其花颜色与花部大小受到的传粉者介导的表型选择。本研究以雌性适合度为指标，评估了花颜色与花部大小所受的表型选择，并通过对比自然传粉花朵与人工补充授粉花朵的选择梯度，检验了传粉者介导的选择效应。在两个物种中，我们均发现了花粉限制的证据，这为传粉者介导的选择提供了基础条件。在二态花色的黄花鸢尾（Iris lutescens）中，尽管色素浓度与花部大小受到选择，但该选择并不依赖于传粉者。而对于多态花色的矮鸢尾（Iris pumila），色素浓度受到传粉者介导的选择压力，但该效应仅存在于其中一种花色形态中。我们的研究结果表明，与目前被广泛接受的花部演化范式相反，传粉者并非这些鸢尾属植物花部性状选择的主要驱动因子。本研究为“传粉者是花部性状选择的主要驱动力”这一主流理论提供了一个反例。