Data from: Odor diversity decreases with inbreeding in the ant Hypoponera opacior

Reduction in heterozygosity can lead to inbreeding depression. This loss of genetic variability especially affects diverse loci, such as immune genes or those encoding recognition cues. In social insects, nestmates are recognized by their odor, i.e. their cuticular hydrocarbon profile. Genes underlying hydrocarbon production are thought to be under balancing selection. If so, inbreeding should result in a loss of chemical diversity. We show here that cuticular hydrocarbon diversity decreases with inbreeding. Studying an ant with a facultative inbreeding lifestyle we found inbred workers to exhibit both a lower number of hydrocarbons and less diverse, that is, less evenly-proportioned profiles. The association with inbreeding was strong for methyl-branched alkanes, which play a major role in nestmate recognition, and for n-alkanes, whereas unsaturated compounds were unaffected. Shifts in allocation strategies with inbreeding in our focal species indicate that these ants can detect their inbreeding level and use this information to adjust their reproductive strategy. Our study is the first to demonstrate that odor profiles can encode information on inbreeding, with broad implications not only for social insects, but for sexual selection and mate choice in general. Odor profiles may constitute an honest signal of inbreeding, a fitness-relevant trait in many species.

杂合性（heterozygosity）降低可引发近交衰退（inbreeding depression）。这种遗传变异的丢失尤其会影响各类基因座，例如免疫基因或编码识别信号（recognition cues）的基因。在社会性昆虫中，同巢伙伴通过其气味——即表皮碳氢化合物图谱（cuticular hydrocarbon profile）——进行识别。学界普遍认为，调控碳氢化合物合成的基因处于平衡选择（balancing selection）作用之下。若果真如此，近交理应导致化学多样性（chemical diversity）的丧失。本研究证实，表皮碳氢化合物的多样性随近交程度加深而降低。我们对一种具有兼性近交（facultative inbreeding）生活史的蚂蚁开展研究，发现近交工蚁的表皮碳氢化合物种类更少，且图谱构成的多样性更低——即各组分比例分布更为不均一。这种关联在甲基支链烷烃（methyl-branched alkanes）和正构烷烃（n-alkanes）中表现尤为显著，而这两类物质在同巢伙伴识别中发挥关键作用；不饱和化合物则未受明显影响。我们的研究物种中，近交引发的资源分配策略改变表明，这些蚂蚁能够检测自身的近交水平，并利用该信息调整繁殖策略。本研究首次证实，气味图谱可编码近交相关信息，其影响范围不仅涵盖社会性昆虫领域，更对一般性的性选择（sexual selection）与配偶选择（mate choice）研究具有广泛启示。气味图谱或可作为近交的诚实信号（honest signal），而近交本身是众多物种中与适合度（fitness）相关的关键性状。