Data from: No inbreeding depression but increased sexual investment in highly inbred ant colonies

Inbreeding can lead to the expression of deleterious recessive alleles and to a subsequent fitness reduction. In Hymenoptera, deleterious alleles are purged in haploid males moderating inbreeding costs. However, in these haplo-diploid species, inbreeding can result in the production of sterile diploid males. We investigated the effects of inbreeding on the individual and colony level in field colonies of the highly inbred ant Hypoponera opacior. In this species, outbreeding winged sexuals and nest-mating wingless sexuals mate during two separate reproductive periods. We show that regular sib-matings lead to high levels of homozygosity and the occasional production of diploid males, which sporadically sire triploid offspring. On the individual level, inbreeding was associated with an increased body size in workers. On the colony level, we found no evidence for inbreeding depression as productivity was unaffected by the level of homozygosity. Instead, inbred colonies altered their allocation strategies by investing more resources into sexuals than into workers. This shift towards sexual production was due to an increased investment in both males and queens, which was particularly pronounced in the dispersive generation. The absence of inbreeding depression combined with increased reproductive investment, especially in outbreeding sexuals, suggest that these ants have evolved active strategies to regulate the extent and effects of frequent inbreeding.近交可导致有害隐性等位基因（deleterious recessive alleles）的表达，进而引发适合度下降。在膜翅目（Hymenoptera）昆虫中，单倍体雄性可清除有害等位基因，从而缓解近交成本。然而，在这类单倍二倍体物种中，近交却可能产生不育的二倍体雄性。我们针对高度近交的凹唇厚结猛蚁（Hypoponera opacior）的野外群体，探究了近交对个体及群体水平的影响。该物种存在两类生殖事件：远交的有翅繁殖蚁，以及在巢内完成交配的无翅繁殖蚁，二者分别在两个独立的生殖周期内进行交配。研究结果显示，常规同胞交配会导致极高的纯合性水平，并偶发产生二倍体雄性；此类雄性偶尔可产生三倍体后代。在个体层面，近交与工蚁体型增大存在显著关联。在群体层面，未发现近交衰退（inbreeding depression）的证据——群体生产力不受纯合性水平的影响。与之相反，近交群体改变了资源分配策略，相较于工蚁，向有性生殖个体投入了更多资源。这种向有性生产的资源倾斜，源于对雄蚁和蚁后两者的投入均有所增加，且在扩散世代中这一现象尤为显著。未出现近交衰退，且繁殖投入（尤其是针对远交繁殖蚁的投入）有所提升，这表明这类蚂蚁已演化出主动调控频繁近交的程度及其影响的策略。