Data from: Patterns of paternity skew among polyandrous social insects: What can they tell us about the potential for sexual selection?

Monogamy results in high genetic relatedness among offspring and thus it is generally assumed to be favoured by kin selection. Female multiple mating (polyandry) has nevertheless evolved several times in the social Hymenoptera (ants, bees and wasps), and a substantial amount of work has been conducted to understand its costs and benefits. Relatedness and inclusive fitness benefits are, however, not only influenced by queen mating frequency but also by paternity skew, which is a quantitative measure of paternity biases among the offspring of polyandrous females. We performed a large scale phylogenetic analysis of paternity skew across polyandrous social Hymenoptera. We found a general and significant negative association between paternity frequency and paternity skew. High paternity skew, which increases relatedness amongst colony members and thus maximizes inclusive fitness gains, characterized species with low paternity frequency. However, species with highly polyandrous queens had low paternity skew, with paternity equalized amongst potential sires. Equal paternity shares among fathers are expected to maximize fitness benefits derived from genetic diversity among offspring. We discuss the potential for post-copulatory sexual selection to influence patterns of paternity in social insects, and suggest that sexual selection may have played a key, yet overlooked role in social evolution.

单配偶制可提升后代间的遗传相关性，因此学界普遍认为该策略可通过亲缘选择（kin selection）获得青睐。尽管如此，社会性膜翅目（social Hymenoptera，涵盖蚂蚁、蜜蜂与胡蜂）中已多次演化出雌性多次交配，即一妻多夫制（polyandry）的现象，目前已有大量研究致力于阐明其演化代价与收益。然而，亲缘相关性与广义适合度（inclusive fitness）收益不仅受蜂王交配频次的影响，还受父性偏倚（paternity skew）的调控——该指标是量化一妻多夫雌性后代父权偏差程度的定量参数。我们针对一妻多夫的社会性膜翅目类群开展了大规模系统发育（phylogenetic）分析，以探究父性偏倚的分布模式。研究发现，交配频次与父性偏倚之间普遍存在显著的负相关关系：交配频次较低的类群往往具有较高的父性偏倚，这会提升巢群内成员间的亲缘相关性，进而最大化广义适合度收益；而蜂王高度一妻多夫的类群则父性偏倚程度较低，潜在父本的父权分配相对均等。父本间均等的父权分配，有望通过提升后代的遗传多样性来最大化适合度收益。我们讨论了交配后性选择（post-copulatory sexual selection）对社会性昆虫父权模式的潜在影响，并提出性选择可能在社会演化中发挥了此前被忽视的关键作用。