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 M. 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 characterising younger and non-virgin 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，常被认为与性二型（Sexual Dimorphism）的演化以及物种间信号性状的分化密切相关。体表皮层化合物（Epicuticular Compounds, ECs）是昆虫的重要信号性状，在不同类群及类群内部均存在广泛的变异。本研究以两种性角色反转的甲虫——背斑豆象（Megabruchidius dorsalis）与东京豆象（M. tonkineus）为研究对象，旨在探究其多变量EC谱的变异能否预测雌雄个体的配偶吸引力与交配成功率。结果显示，两个物种的EC谱具有显著差异，且二者的EC谱均呈现出显著的性二型特征；同时，两个物种的个体年龄与交配状态，也可通过EC谱加以区分。两个物种的雌雄个体，其EC谱与吸引力均存在显著关联——这里的吸引力通过交配潜伏期与配偶选择试验中的交配成功率两项指标进行衡量。值得注意的是，描述吸引力的核心多变量向量，在两个物种、两种性别以及选择与非选择试验中均呈现相关性：即无论何种情境下，吸引力的提升均与EC组成的相似多变量改变相关。此外，在两种性别中，该吸引力相关向量均与更偏向雄性的EC谱，以及表征年轻个体与已交配个体的EC谱存在关联，这或许反映了雌雄两性对体质优良个体的普遍偏好。尽管EC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EC谱分化的原因"这一命题。