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.

由交配偏好介导的性选择常被认为是推动性二态性演化以及物种间信号性状分化的关键因素。表皮碳氢化合物（Epicuticular Compounds，ECs）是昆虫重要的信号性状，在不同类群及类群内部均表现出广泛的变异。本研究旨在探究两种性角色反转的甲虫——背甲豆象（Megabruchidius dorsalis）与东京豆象（Megabruchidius tonkineus）——的多变量表皮碳氢化合物谱变异，能否预测雌雄个体的交配吸引力与交配成功率。两个物种的表皮碳氢化合物谱差异显著，且均在表皮碳氢化合物组成上表现出显著的性二态性；此外，两个物种的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均表现出表皮碳氢化合物谱与吸引力之间的显著关联，其中吸引力以交配潜伏期及择偶试验中的成功率作为衡量指标。值得注意的是，描述吸引力的主要多变量向量在两个物种、两种性别，以及选择试验与无选择试验中均呈现相关性：在所有情况下，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，这一代表吸引力的向量均与更具雄性特征的表皮碳氢化合物谱相关，同时也与表征年轻非处女个体的谱型相关，这或许反映了两性均对高质量个体存在普遍偏好。尽管表皮碳氢化合物组成受到显著的性选择作用，但我们并未发现支持"性选择是导致这两个物种间表皮碳氢化合物组成分化的原因"这一观点的证据。