The operation of sexual selection depends on ecological conditions. Thus, changes in environmental conditions because of human activities can alter the strength and direction of sexual selection, with implications for evolutionary trajectories and the viability of populations. We show that aquatic algal blooms can relax the operation of sexual selection by influencing which males are available to attract females. This is by influencing the ability of males to maintain a resource needed in mate attraction. When we exposed two competing threespine stickleback males Gasterosteus aculeatus, whose attractiveness to females was known, to either clear or algal‐turbid water, nest abandonment was more common in clear water, and it was usually the unattractive male that abandoned his nest. In turbid water, on the other hand, nest abandonments were less common and when they occurred, the probability increased that the attractive male abandoned his nest, and that the unattractive male subsequently occupied it. This change in the composition of nesting males increased the mating success of unattractive males. Thus, our results reveal a new mechanism through which habitat deterioration can influence sexual selection, by altering success in the competition for a resource critical in mate attraction, a territory with a nest in this case. This could be a common mechanism, considering the prevalence of resource competition in mate choice systems. On a broader level, our results emphasise the importance of considering the impact of environmental changes on the outcome of resource competition when investigating the influence that environmental disturbances have on the operation of sexual selection and thereby on evolutionary processes and population dynamics.

中文翻译：

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栖息地恶化减轻了三棘棘背鱼的资源竞争和性选择

性选择的操作取决于生态条件。因此，由于人类活动引起的环境条件的改变会改变性选择的强度和方向，从而影响进化轨迹和人口的生存能力。我们表明，水生藻华可以通过影响哪些雄性可吸引雌性而放松性选择的操作。这是通过影响雄性维持伴侣吸引所需资源的能力。当我们暴露了两只相互竞争的三脊棘背式雄性Gasterosteus aculeatus众所周知，它对雌性的吸引力是清澈的或藻类混浊的水，在清澈的水中，鸟巢的遗弃更为常见，通常是没有吸引力的雄性放弃了其巢穴。另一方面，在混浊的水中，鸟巢遗弃不那么常见，当它们发生时，有吸引力的雄性抛弃他的巢，而没有吸引力的雄性随后占领它的可能性增加。筑巢雄性的这种变化增加了没有吸引力的雄性的交配成功率。因此，我们的研究结果揭示了一种新的机制，通过改变对配偶吸引至关重要的资源（在这种情况下为带有巢穴的区域）争夺关键资源的竞争，栖息地恶化可以影响性别选择。考虑到配偶选择系统中资源竞争的普遍性，这可能是一种常见的机制。