Data from: The tale of the shrinking weapon: seasonal changes in nutrition affect weapon size and sexual dimorphism, but not contemporary evolution

Sexually selected traits are often highly variable in size within populations due to their close link with the physical condition of individuals. Nutrition has a large impact on physical condition, and thus, any seasonal changes in nutritional quality are predicted to alter the average size of sexually selected traits as well as the degree of sexual dimorphism in populations. However, although traits affected by mate choice are well studied, we have a surprising lack of knowledge of how natural variation in nutrition affects the expression of sexually selected weapons and sexual dimorphism. Further, few studies explicitly test for differences in the heritability and mean-scaled evolvability of sexually selected traits across conditions. We studied Narnia femorata (Hemiptera: Coreidae), an insect where males use their hind legs as weapons and the femurs are enlarged, to understand the extent to which weapon expression, sexual dimorphism and evolvability change across the actual range of nutrition available in the wild. We found that insects raised on a poor diet (cactus without fruit) are nearly monomorphic, whereas those raised on a high-quality diet (cactus with ripe fruit) are distinctly sexually dimorphic via the expression of large hind leg weapons in males. Contrary to our expectations, we found little evidence of a potential for evolutionary change for any trait measured. Thus, although we show weapons are highly condition dependent, and changes in weapon expression and dimorphism could alter evolutionary dynamics, our populations are unlikely to experience further evolutionary changes under current conditions.

性选择性状（sexually selected traits）在种群内常表现出高度的体型变异，这与其与个体身体状态的紧密关联密不可分。营养状况对个体身体状态影响显著，因此理论上，营养质量的季节性变化可改变种群中性选择性状的平均体型，以及种群内的性二态性（sexual dimorphism）程度。然而，尽管受配偶选择影响的性状已得到充分研究，但令人意外的是，我们对自然状态下的营养变异如何影响性选择武器（sexually selected weapons）的表达以及性二态性仍知之甚少。此外，鲜有研究明确检验不同环境下性选择性状的遗传力（heritability）与均值尺度可进化性（mean-scaled evolvability）是否存在差异。
我们以红足亮猎蝽（Narnia femorata，半翅目：缘蝽科）为研究对象，该物种的雄性以后足作为武器，且股节显著膨大，以此探究在野外实际存在的营养梯度下，武器表达、性二态性以及可进化性的变化幅度。我们发现，取食低质量食物（无果实的仙人掌）的种群几乎呈单态，而取食高质量食物（带有成熟果实的仙人掌）的种群则因雄性后足武器的显著发育而呈现出清晰的性二态。与我们的预期相悖的是，我们未发现所测任何性状存在进化改变的潜力。因此，尽管我们证实了武器发育高度依赖身体状态，且武器表达与二态性的变化可能改变进化动态，但当前环境下，我们的研究种群不太可能发生进一步的进化改变。