Data from: Experimental manipulation reveals a trade-off between weapons and testes

Theory predicts a trade-off between sexually-selected weapons used to secure mates and post-copulatory traits used to maximize fertilization success. However, individuals that have a greater capacity to acquire resources from the environment may invest more in both pre- and post-copulatory traits, and trade-offs may not be readily apparent. Here, we manipulate the phenotype of developing individuals to examine allocation trade-offs between weapons and testes in Mictis profana (Hemiptera: Coreidae), a species where the hind legs are sexually selected weapons used in contests over access to females. We experimentally prevented males from developing weapons by inducing them to autotomize their hind legs before the final molt to adulthood. We compared trait expression in this group to males where autotomy was induced in the mid legs, which are presumably not under sexual selection to the same extent. We found males without weapons invested proportionally more in testes mass than those with their mid legs removed. Males that developed to adulthood without weapons did not differ from the mid leg removal group in other traits potentially under pre-copulatory sexual selection, other post-copulatory traits, or naturally selected traits. In addition, a sample of adult males from the same population in the wild revealed a positive correlation between investment in testes and weapons. Our study presents a critical contribution to a growing body of literature suggesting the allocation of resources to pre- and post-copulatory sexual traits is influenced by a resource allocation trade-off and that this trade-off may only be revealed with experimental manipulation.理论预测，用于争夺配偶的性选择武器（sexually-selected weapons）与用于最大化受精成功率的交配后性状（post-copulatory traits）之间存在资源权衡。然而，具备更强环境资源获取能力的个体，可同时在交配前与交配后性状上投入更多资源，因此这类权衡往往难以被直接观测到。本研究通过调控发育个体的表型，探究广腹同缘蝽（Mictis profana，Hemiptera: Coreidae）的性选择武器与精巢（testes）间的资源分配权衡——该物种的后足为用于雌性配偶争夺的性选择武器。我们通过诱导雄性在最后一次蜕皮（final molt）至成虫前自切其后足，使其无法发育出性选择武器，并将该组雄性的性状表达与另一组（诱导自切中足，这类足通常认为不受同等程度的性选择作用）进行对比分析。结果显示，缺失性选择武器的雄性，其精巢质量的相对投入显著高于中足自切组雄性。未发育出性选择武器的雄性，在其他可能受交配前性选择、其他交配后性状或自然选择作用的性状上，与中足自切组并无显著差异。此外，对该野生种群成年雄性的抽样调查表明，精巢投入与武器投入之间呈正相关关系。本研究为日益增长的相关学术文献提供了关键佐证：资源向交配前与交配后性性状的分配，受资源权衡机制调控，且这类权衡仅能通过实验操控得以揭示。