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.

单群蚁的蚁后数量与每只蚁后的交配次数，是决定蚁群遗传结构的两大核心因素，厘清二者间的关联对于社会演化研究至关重要。多后制（Polygyny）与多配制（Polyandry）对立假说提出，二者之间应呈负相关关系，因为两者均会提升蚁群内部的遗传变异水平，且各自携带演化成本。然而，该假说长期存在争议，且始终缺乏种内层面的实证支持。本研究以澳大利亚牛头犬蚁（Myrmecia brevinoda）为对象，探究其蚁群遗传结构：该蚁种的单群蚁后数量介于1至6只之间，多后制蚁群内的同巢蚁后平均亲缘系数为$r_{qq}=0.171pm0.019$，但蚁后与其配偶间的整体亲缘系数与零无显著差异（$r_{qm}=0.037pm0.030$）；研究推断每只蚁后可与1至10只雄蚁交配，且蚁巢间未出现基于地理距离的遗传分化，表明该蚁种主要通过独立奠基建立新蚁群。本研究结果符合该假说：单群蚁后数量与估算的蚁后交配次数呈显著负相关（斯皮尔曼等级相关系数（Spearman rank correlation）$R=-0.490$，$P=0.028$）。因此，本研究为该长期争议的假说提供了罕见的种内实证支持。我们认为，多次交配带来的高额成本，以及多次交配对蚁群内部遗传多样性的显著影响，或是多后制与多配制间负相关关系的核心驱动因素；未来若要通过实证检验该假说，应重点关注这两个关键维度。