Data from: Low levels of hybridization in two species of African driver ants

Hybridization in ants can have consequences different from those observed in most other species, with many of the potential deleterious effects being mitigated due to haplodiploidy and eusociality. In some species where colonies are either headed by multiple queens or single queens that mate with many males, hybridization is associated with genetic caste determination, where hybrids develop into workers and purebred individuals develop into queens. A previous study suggested that hybridization occurs between two Dorylus army ant species with multiply mate queens. However, the extent and exact pattern of hybridization has remained unclear, and its possible effect on caste determination has not been investigated. In this study we aimed to determine the extent and direction of hybridization by measuring how frequently hybrids occur in colonies of both species, and to investigate the possibility of genetic caste determination. We show that hybridization is bidirectional and occurs at equal rates in both species. Hybrid workers make up only 1-2% of the population, and interspecific matings represent approximately 2% of all matings in both species. This shows that, while interspecific matings that give rise to worker offspring occur regularly, they are much rarer than intraspecific mating. Finally, we find no evidence of an association between hybridization and genetic caste determination in this population. This means that genetic caste determination is not a necessary outcome of hybridization in ants, even in species where queens mate with multiple males.

蚂蚁的杂交效应可能与多数其他物种存在显著差异，得益于单倍二倍性（haplodiploidy）与真社会性（eusociality），诸多潜在的有害效应得以缓解。在部分蚁群由多后制蚁后统领，或是由与多雄交配的单后制蚁后统领的物种中，杂交与遗传品级决定（genetic caste determination）相关：杂交后代发育为工蚁，纯种个体则发育为蚁后。既往一项研究提示，两种由多雄交配蚁后统领的矛蚁属（Dorylus）行军蚁物种间存在杂交现象。然而，杂交的发生范围与精确模式仍不明确，其对品级决定的潜在影响也尚未得到探究。本研究旨在通过检测两个物种各蚁群中杂交个体的出现频率，明确杂交的发生范围与方向，并探究遗传品级决定的可能性。研究结果显示，杂交为双向发生，且在两个物种中的发生概率均等。杂交工蚁仅占种群总个体数的1%~2%，且种间交配约占两个物种所有交配事件的2%。这表明，尽管可产生工蚁后代的种间交配确实定期发生，但其发生频率远低于种内交配。此外，本研究未在该种群中发现杂交与遗传品级决定存在关联的证据。这意味着，即便在蚁后与多雄交配的蚁类中，遗传品级决定也并非蚂蚁杂交的必然结果。