Exaggerated and conspicuous sexually selected traits are often costly to produce and maintain. Costly traits are expected to show resource-dependent expression, since limited resources prevent animals from investing maximally in multiple traits simultaneously. However, there may be critical periods during an individual’s life where the expression of traits is altered if resources are limited. Moreover, costly sexual traits may arise from sexual selection acting both before (pre-copulatory) and after mating (post-copulatory). Gaining a robust understanding of resource-dependent trait expression therefore requires an approach that examines both episodes of sexual selection after resource limitation during different times in an individual’s life. Yet few studies have taken such an approach. Here, we examine how resource restriction influences a set of pre- and post-copulatory traits in male pygmy halfbeaks (Dermogenys collettei), which invest in sexual ornaments and routinely engage in male–male contests and sperm competition. Critically, we examined responses in males when resources were restricted during development and after reaching sexual maturity. Both pre- and post-copulatory traits are resource-dependent in male halfbeaks. Body size, beak size, courtship behavior, and testes size were reduced by diet restriction, while, unexpectedly, the restricted-diet group had a larger area of red color on the beak and fins after diet treatment. These patterns were generally consistent when resources were restricted during development and after reaching sexual maturity. The study reinforces the role of resource acquisition in maintaining variation among sexual traits.

中文翻译：

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胎生鱼雄性性状的资源依赖性投资

夸大和显眼的性选择特征往往需要高昂的生产和维持成本。昂贵的性状预计会表现出资源依赖性表达，因为有限的资源会阻止动物同时最大程度地投资于多种性状。然而，如果资源有限，个人生命中可能存在关键时期，此时特征的表达会发生改变。此外，昂贵的性特征可能来自交配前（交配前）和交配后（交配后）的性选择。因此，要深入了解资源依赖性特征表达，就需要一种方法来检查个体生命中不同时期资源限制后性选择的两个阶段。然而，很少有研究采用这种方法。这里，我们研究了资源限制如何影响男性侏儒半喙 (Dermogenys collettei) 的一组交配前和交配后特征，它们投资于性装饰品并经常参与雄性竞赛和精子竞争。至关重要的是，我们检查了雄性在发育过程中和达到性成熟后资源受到限制时的反应。交配前和交配后的特征在雄性半喙中都依赖于资源。体型、喙的大小、求偶行为和睾丸的大小都因饮食限制而减小，而出乎意料的是，饮食限制组在饮食治疗后的喙和鳍上出现了更大面积的红色。当资源在发育过程中和达到性成熟后受到限制时，这些模式通常是一致的。