Data from: Intraspecific support for the polygyny-vs.-polyandry hypothesis in the bulldog ant Myrmecia brevinoda

The number of queens per colony and the number of matings per queen are the most important determinants of the genetic structure of ant colonies, and understanding their interrelationship is essential to the study of social evolution. The polygyny-versus-polyandry hypothesis argues that polygyny and polyandry should be negatively associated since both can result in increased intracolonial genetic variability and have costs. However, evidence for this long-debated hypothesis has been lacking at the intraspecific level. Here, we investigated the colony genetic structure in the Australian bulldog ant Myrmecia brevinoda. The numbers of queens per colony varied from 1 to 6. Nestmate queens within polygynous colonies were on average related (rqq = 0.171±0.019), but the overall relatedness between queens and their mates was indistinguishable from zero (rqm = 0.037±0.030). Queens were inferred to mate with 1 to 10 males. A lack of genetic isolation by distance among nests indicated the prevalence of independent colony foundation. In accordance with the polygyny-versus-polyandry hypothesis, the number of queens per colony was significantly negatively associated with the estimated number of matings (Spearman rank correlation R = -0.490, P = 0.028). This study thus provides rare intraspecific evidence for the polygyny-versus-polyandry hypothesis. We suggest that high costs of multiple matings and the strong effect of multiple mating on intracolonial genetic diversity may be essential to the negative association between polygyny and polyandry, and that any attempt to empirically test this hypothesis should place emphasis upon these two key underlying aspects.

每蚁群的蚁后数量与每蚁后的交配次数，是决定蚁群遗传结构的两大核心要素，厘清二者间的关联对于社会演化研究至关重要。多后制与一妻多夫制权衡假说（polygyny-versus-polyandry hypothesis）提出，多后制与一妻多夫制应呈负相关关系：二者均会提升蚁群内部的遗传变异程度，且均存在适应性代价。然而，这一长期存在争议的假说一直缺乏种内水平的实证支持。本研究以澳大利亚牛头犬蚁*Myrmecia brevinoda*为研究对象，对其蚁群遗传结构展开了调查。该蚁种的每蚁群蚁后数量介于1至6只之间。多后制蚁群内的同巢蚁后平均亲缘系数为$r_{qq}=0.171pm0.019$，但蚁后与其交配雄蚁之间的整体亲缘系数与0无显著差异（$r_{qm}=0.037pm0.030$）。研究推断，每只蚁后可与1至10只雄蚁交配。蚁群间未检测到基于地理距离的遗传分化，这表明该蚁种主要通过独立建巢方式繁衍。与该假说的预测相符，每蚁群的蚁后数量与估测的交配次数呈显著负相关（斯皮尔曼等级相关系数$R=-0.490$，$P=0.028$）。因此，本研究为多后制与一妻多夫制权衡假说提供了罕见的种内实证支持。我们认为，多次交配的高昂代价以及多次交配对蚁群内部遗传多样性的显著影响，或是多后制与一妻多夫制呈负相关的核心机制；未来若要通过实验验证该假说，应重点关注这两个关键维度。