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（inbreeding）可引发有害隐性等位基因的表达，并导致后续的适合度（fitness）下降。在膜翅目（Hymenoptera）昆虫中，单倍体雄性能够清除有害等位基因，从而缓解近交带来的成本。然而，在这类单倍二倍体（haplo-diploid）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蚂蚁物种光泽前结蚁（Hypoponera opacior）的野外蚁群，探究了近交在个体水平与蚁群水平上的影响。该物种存在两类生殖蚁：远交型具翅生殖蚁与巢内交配型无翅生殖蚁，二者会在两个独立的生殖周期内完成交配。研究结果表明，常规的同胞交配会导致高水平的纯合性（homozygosity），且偶会产生二倍体雄性，这类雄性偶尔可与雌性交配并产生三倍体后代。在个体层面，近交与工蚁体型增大存在显著关联。在蚁群层面，我们未发现近交衰退（inbreeding depression）的证据：蚁群生产力不受纯合性水平的影响。与之相反，近交蚁群调整了资源分配策略，相较于工蚁，其向生殖蚁投入了更多资源。这种向生殖生产的资源倾斜，同时体现在对雄性与蚁后的资源投入增加上，且在扩散型生殖世代中这一现象尤为突出。未出现近交衰退，且生殖投入（尤其是对远交型生殖蚁的投入）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与影响的有效策略。