Data from: Condition-dependent expression of pre- and postcopulatory sexual traits in guppies

These are phenotypic data collected for male guppies fed different diets to expose condition dependence in sexually selected traits.

Female choice can impose persistent directional selection on male sexually selected traits, yet such traits often exhibit high levels of phenotypic variation. One explanation for this paradox is that if sexually selected traits are costly, only the fittest males are able to acquire and allocate the resources required for their expression. Furthermore, because male condition is dependent on resource allocation, condition dependence in sexual traits is expected to underlie trade-offs between reproduction and other life-history functions. In this study we test these ideas by experimentally manipulating diet quality (carotenoid levels) and quantity in the guppy (Poecilia reticulata), a livebearing freshwater fish that is an important model for understanding relationships between pre- and post-copulatory sexually selected traits. Specifically, we test for condition dependence in the expression of pre- and postcopulatory sexual traits (behavior, ornamentation, sperm traits) and determine whether diet manipulation mediates relationships among these traits. Consistent with prior work we found a significant effect of diet quantity on the expression of both pre- and postcopulatory male traits; diet-restricted males performed fewer sexual behaviors and exhibited significant reductions in color ornamentation, sperm quality, sperm number, and sperm length than those fed ad libitum. However, contrary to our expectations, we found no significant effect of carotenoid manipulation on the expression of any of these traits, and no evidence for a trade-off in resource allocation between pre- and postcopulatory episodes of sexual selection. Our results further underscore the sensitivity of behavioral, ornamental, and ejaculate traits to dietary stress, and highlight the important role of condition dependence in maintaining the high variability in male sexual traits.

本数据集为饲喂不同饮食的雄性孔雀鱼采集的表型数据，旨在揭示性选择性状（sexually selected traits）的条件依赖性（condition dependence）。雌性选择可对雄性性选择性状施加持续的定向选择，但这类性状往往表现出极高的表型变异水平。针对这一悖论的一种解释是：若性选择性状存在演化成本，则仅健康状态最优的雄性能够获取并分配其表达所需的资源。此外，由于雄性健康状态依赖于资源分配，因此性性状的条件依赖性被认为是繁殖与其他生活史功能之间权衡关系的基础。本研究以胎生淡水鱼类孔雀鱼（*Poecilia reticulata*）——作为研究交配前（pre-copulatory）与交配后（post-copulatory）性选择性状关系的重要模式物种——为研究对象，通过实验操控其饮食质量（类胡萝卜素（carotenoid）水平）与摄入量，对上述假说进行验证。具体而言，本研究旨在检验交配前与交配后性性状（行为、装饰性状、精子性状）表达的条件依赖性，并明确饮食操控是否会介导这些性状之间的关联。与先前研究结果一致，我们发现饮食摄入量对雄性交配前与交配后性性状的表达均存在显著影响：饮食受限的雄性表现出更少的性行为，且其体色装饰、精子质量、精子数量及精子长度均显著低于自由采食（ad libitum）组个体。但与我们的预期相悖的是，类胡萝卜素操控对上述所有性状的表达均无显著影响，且未发现交配前与交配后性选择阶段之间存在资源分配权衡的证据。本研究结果进一步证实了行为性状、装饰性状与精液性状对饮食胁迫的敏感性，并凸显了条件依赖性在维持雄性性性状高变异水平中的重要作用。