Summary Hybrid zones provide natural experimental settings to test hypotheses about species divergence. We concentrated on a hybrid swarm in which oil‐collecting bees and flower‐pecking birds act as pollinators of two Calceolaria species. We asked whether both pollinators contributed to flower divergence by differentially promoting prezygotic fitness at the phenotypic extremes that represent parentals. We studied pollinator‐mediated selection on phenotypic traits critical in plant–pollinator mechanical interaction, namely plant height, reward‐to‐stigma distance, and flower shape. We utilised the quantity and quality of pollen deposited as fitness measures and distinguished between the contribution of the two pollinator types. Results showed uni‐ and bivariate disruptive selection for most traits through pollen grains deposited by both pollinators. Bird‐mediated fitness favoured low plants with a long reward‐to‐stigma distance and a straight corolla, while bee‐mediated fitness favoured tall plants with a short reward‐to‐stigma distance and curved corolla. In addition, stabilising selection at one end of the phenotypic range showed a bird‐mediated reproductive asymmetry within the swarm. The disruptive pattern was countered, albeit weakly, by hybrids receiving higher‐quality pollen on the stigmas. Results suggest that pollinator‐mediated selection promotes divergence of integrated flower phenotypes mechanically adjusted either to bees or birds underscoring the importance of pollinator specialisation in diversification.

中文翻译：

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具有对比传粉媒介的两种蒲包花物种之间的杂交区的表型选择模式：实地调查和适应性评估的见解

概括 杂交区提供了自然的实验环境来检验有关物种分化的假设。我们集中研究了一个混合群，其中采油蜂和啄花鸟充当两种昆虫的传粉者蒲包花物种。我们询问这两种传粉媒介是否通过在代表亲本的表型极端上差异性地促进合子前的适应性而导致花的分化。 我们研究了传粉媒介介导的对植物与传粉媒介机械相互作用至关重要的表型性状的选择，即株高、奖赏到柱头距离和花形。我们利用沉积花粉的数量和质量作为适应性指标，并区分两种传粉媒介类型的贡献。 结果表明，通过两种传粉者沉积的花粉粒，大多数性状发生单变量和双变量破坏性选择。鸟类介导的适应性有利于具有较长奖励到柱头距离和直花冠的低矮植物，而蜜蜂介导的适应性则有利于具有较短奖励到柱头距离和弯曲花冠的高大植物。此外，表型范围一端的稳定选择显示了群体内鸟类介导的生殖不对称性。通过在柱头上接受更高质量的花粉，这种破坏性的模式得到了抵消，尽管效果很弱。 结果表明，传粉媒介介导的选择促进了机械调整到蜜蜂或鸟类的综合花表型的分化，强调了传粉媒介专业化在多样化中的重要性。