Data from: Sexual dimorphism in epicuticular compounds despite similar sexual selection in sex role-reversed seed beetles

Sexual selection imposed by mating preferences is often implicated in the evolution of both sexual dimorphism and divergence between species in signalling traits. Epicuticular compounds (ECs) are important signalling traits in insects and show extensive variability among and within taxa. Here, we investigate whether variation in the multivariate EC profiles of two sex role-reversed beetle species, Megabruchidius dorsalis and Megabruchidius tonkineus, predicts mate attractiveness and mating success in males and females. The two species had highly distinct EC profiles and both showed significant sexual dimorphism in ECs. Age and mating status in both species were also distinguishable by EC profile. Males and females of both species showed significant association between their EC profile and attractiveness, measured both as latency to mating and as success in mate-choice trials. Remarkably, the major multivariate vector describing attractiveness was correlated in both species, both sexes, and in both choice and no-choice experiments such that increased attractiveness was in all cases associated with a similar multivariate modification of EC composition. Furthermore, in both sexes this vector of attractiveness was associated with more male-like EC profiles, as well as those characterizing younger and nonvirgin individuals, which might reflect a general preference for individuals of high condition in both sexes. Despite significant sexual selection on EC composition, however, we found no support for the proposition that sexual selection is responsible for divergence in ECs between these species.由择偶偏好施加的性选择，常被认为与性二型性以及物种间信号性状的演化分化密切相关。表皮碳氢化合物（Epicuticular Compounds, ECs）是昆虫重要的信号性状，且在不同类群及类群内部均表现出广泛的变异。本研究以两种性角色反转的甲虫物种——背大臀豆象（Megabruchidius dorsalis）与通卡大臀豆象（Megabruchidius tonkineus）——为研究对象，探究其多变量表皮碳氢化合物谱的变异是否能够预测雌雄个体的配偶吸引力与交配成功率。两个物种的表皮碳氢化合物谱具有显著差异，且二者的表皮碳氢化合物均表现出显著的性二型性。此外，两个物种的个体年龄与交配状态也可通过表皮碳氢化合物谱加以区分。两个物种的雌雄个体，其表皮碳氢化合物谱均与配偶吸引力存在显著关联；配偶吸引力通过交配潜伏期与择偶试验中的交配成功率两个指标进行量化。值得注意的是，描述配偶吸引力的主要多变量向量在两个物种、两种性别以及择偶与非择偶试验中均呈现相关性：在所有情境下，吸引力的提升均与表皮碳氢化合物组成的相似多变量改变相关联。此外，在两种性别中，该与吸引力相关的多变量向量均与更偏向雄性的表皮碳氢化合物谱，以及表征年轻且已交配个体的谱型相关联，这或许反映了两性对优质状态个体的普遍偏好。尽管表皮碳氢化合物组成受到了显著的性选择作用，但本研究并未发现证据支持“性选择是导致这两个物种表皮碳氢化合物谱分化的原因”这一命题。