Data from: Novel host plant leads to the loss of sexual dimorphism in a sexually-selected male weapon

In this time of massive global change, species are now frequently interacting with novel players. Greater insight into the impact of these novel interactions on traits linked to fitness is essential, because effects on these traits can hinder population existence or promote rapid adaptation. Sexually-selected weapons and ornaments frequently influence fitness and often have heightened condition-dependence in response to nutrition. Condition-dependence in response to different ecological conditions, a form of developmental plasticity, may be responsible for much of the intraspecific variation in sexually selected ornaments and weapons in wild populations. Here we examined the consequences of developing on a novel plant for the expression of size and shape in the leaf-footed cactus bug Narnia femorata (Hemiptera: Coreidae). The males of this species possess enlarged, sexually-dimorphic femurs on their hind legs. These legs are used as weapons in male-male contests. Females are typically larger in overall body size. Our study revealed that developing upon a novel host can lead to pronounced phenotypically plastic change in sexually-dimorphic traits. Male hind femurs were greatly impacted by the novel diet to the extent that the sexual dimorphism in hind femurs was lost. Further, dimorphism in body size increased, as males became tiny adults while females better maintained their body size. These patterns underscore the complex effects that novel species interactions may have on sexual phenotypes.在全球巨变的当下，物种正频繁与新兴交互对象产生接触。深入解析这些新型交互对与适合度相关性状的影响至关重要，因为这类影响既可能阻碍种群存续，也可能推动快速适应性演化。性选择塑造的武器与装饰结构通常会影响个体适合度，且往往对营养条件表现出更强的条件依赖性。响应不同生态条件的条件依赖性作为一种发育可塑性形式，或许是野生种群中性选择相关武器与装饰出现大量种内变异的主要原因。本研究以叶足仙人掌蝽（Narnia femorata，半翅目：姬缘蝽科）为对象，探究了其在新型寄主植物上发育时，体型与形状表达所受的影响。该物种的雄性后足腿节膨大，呈现典型的性二态性，这类后足会被用于雄性间的争斗；雌性的整体体型通常大于雄性。本研究发现，在新型寄主上发育会导致性二态性状出现显著的表型可塑性变化：雄性后足腿节受新寄主饮食的影响极为显著，甚至完全消除了后足腿节的性二态性；与此同时，体型的二态性反而增强——雄性成虫体型偏小，而雌性则较好维持了自身的体型大小。这些结果凸显了新型物种交互对性表型可能产生的复杂效应。