Data from: Sexually antagonistic evolution caused by male-male competition in the pistil

While sexual selection and sexual conflict are important evolutionary forces in animals, their significance in plants is uncertain. In hermaphroditic organisms, such as many plants, sexual conflict may occur both between mating partners (inter-locus conflict) and between male and female sex roles within an individual (intra-locus conflict). We performed experimental evolution, involving lines that were crossed with either one or two pollen donors (monogamous or polyandrous lines), in the hermaphroditic plant (<i>Collinsia heterophylla</i>) where early fertilizations are associated with female fitness costs (reduced seed set). Artificial polyandry for four generations resulted in enhanced pollen performance and increased female fitness costs compared to the monogamous and source (starting material) lines. Female fitness was also reduced in the monogamous line, indicating a possible trade-off between sex roles, resulting from early pollination. We performed a second experiment to investigate a potential harming effect of pollen performance on seed set. We found that high siring success of early-arriving pollen competing with later-arriving pollen was associated with high female fitness costs, consistent with an inter-locus sexual conflict. Our study provides evidence for the importance of sexual selection in shaping evolution of plant reproductive strategies, but also pinpoints the complexity of sexual conflict in hermaphroditic species.

尽管性选择（sexual selection）与性冲突（sexual conflict）是动物界重要的进化动力，但二者在植物类群中的重要性仍尚不明确。对于多数植物这类雌雄同体（hermaphroditic）生物而言，性冲突既可发生于交配伴侣之间（即位点间冲突，inter-locus conflict），也可存在于个体内雄性与雌性生殖功能之间（即位点内冲突，intra-locus conflict）。本研究以早期受精会引发雌性适合度代价（结籽率降低）的雌雄同体植物异色柯林草（Collinsia heterophylla）为实验材料，开展实验进化研究：将实验株系分别与1个或2个花粉供体（pollen donors）杂交，构建单配系（monogamous lines）与多配系（polyandrous lines）。经4代人工多配处理后，与单配系及原始起始株系（source lines）相比，多配系的花粉性能显著提升，但雌性适合度代价也同步升高。单配系的雌性适合度同样出现下降，这表明早期授粉可能引发不同生殖功能间的权衡效应。为进一步探究花粉性能对结籽率的潜在伤害效应，我们开展了第二项实验。结果发现，当早到花粉与晚到花粉竞争时，早到花粉的高父本成功率（siring success）与较高的雌性适合度代价显著相关，这与位点间性冲突的理论预期相符。本研究证实了性选择在塑造植物生殖策略演化过程中的重要性，同时也凸显了雌雄同体物种中性冲突的复杂性。