Preference divergence is thought to contribute to reproductive isolation. Ecology can alter the way selection acts on female preferences, making them most likely to diverge when ecological conditions vary among populations. We present a novel mechanism for ecologically dependent sexual selection, termed ‘the ecological stage’ to highlight its ecological dependence. Our hypothesized mechanism emphasizes that males and females interact over mating in a specific ecological context, and different ecological conditions change the costs and benefits of mating interactions, selecting for different preferences in distinct environments and different male traits, especially when traits are condition dependent. We test key predictions of this mechanism in a sympatric three-spine stickleback species pair. We used a maternal half-sib split-clutch design for both species, mating females to attractive and unattractive males and raising progeny on alternate diets that mimic the specialized diets of the species in nature. We estimated the benefits of mate choice for an indicator trait (male nuptial colour) by measuring many fitness components across the lifetimes of both sons and daughters from these crosses. We analysed fitness data using a combination of aster and mixed models. We found that many benefits of mating with high-colour males depended on both species and diet. These results support the ecological stage hypothesis for sticklebacks. Finally, we discuss the potential role of this mechanism for other taxa and highlight its ability to enhance reproductive isolation as speciation proceeds, thus facilitating the evolution of strong reproductive isolation.

This article is part of the theme issue ‘Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers'.

偏好差异被认为是导致生殖隔离的原因。生态可以改变选择对女性偏好的作用方式，当生态条件因种群而异时，它们最有可能发生分歧。我们提出了一种新的生态依赖性选择机制，称为“生态阶段”，以突出其生态依赖。我们的假设机制强调雄性和雌性在特定的生态环境中通过交配相互作用，不同的生态条件会改变交配相互作用的成本和收益，在不同的环境和不同的雄性特征中选择不同的偏好，尤其是当特征依赖于条件时。我们在同域三刺棘鱼物种对中测试了这种机制的关键预测。我们为这两个物种使用了母系半同胞分裂离合器设计，将雌性与有吸引力和没有吸引力的雄性交配，并在模仿自然界物种特殊饮食的替代饮食中饲养后代。我们通过测量来自这些杂交的儿子和女儿一生中的许多健康成分来估计配偶选择对指示性特征（男性婚礼颜色）的好处。我们使用 aster 和混合模型的组合分析了健身数据。我们发现与高颜色雄性交配的许多好处取决于物种和饮食。这些结果支持棘鱼的生态阶段假说。最后，我们讨论了这种机制对其他分类群的潜在作用，并强调了它在物种形成过程中增强生殖隔离的能力，

本文是主题问题“走向物种形成的完成：超越第一道障碍的生殖隔离的进化”的一部分。