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

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 whet...

雌性选择可对雄性性选择性状（sexually selected traits）施加持续的定向选择（directional selection），但这类性状往往呈现出高水平的表型变异（phenotypic variation）。针对这一悖论的一种解释为：若性选择性状存在发育成本，则仅健康状况最优的雄性能够获取并调配其性状表达所需的资源。此外，由于雄性健康状况依赖于资源分配，因此性性状的健康状况依赖性被认为是繁殖与其他生活史功能（life-history functions）之间权衡关系（trade-offs）的核心基础。本研究以孔雀鱼（guppy，Poecilia reticulata，一种胎生淡水鱼类，亦是探究交配前（pre-copulatory）与交配后（post-copulatory）性选择性状关联的重要模式生物）为实验对象，通过人为操控其日粮的质量（类胡萝卜素水平，carotenoid levels）与数量来验证上述假说。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）的表达是否存在健康状况依赖性，并探究……