No evidence for divergence in male harmfulness or female resistance in response to changes in the opportunity for dispersal

The outcome of sexual conflict can depend on the social environment, as males respond to changes in the inclusive fitness payoffs of harmfulness and harm females less when they compete with familiar relatives. Theoretical models also predict that if limited male dispersal predictably enhances local relatedness while maintaining global competition, kin selection can produce evolutionary divergences in male harmfulness among populations. Experimental tests of these predictions, however, are rare. We assessed rates of dispersal in female and male seed beetles Callosobruchus maculatus, a model species for studies of sexual conflict, in an experimental setting. Females dispersed significantly more often than males, but dispersing males traveled just as far as dispersing females. Next, we used experimental evolution to test whether limiting dispersal allowed the action of kin selection to affect divergence in male harmfulness and female resistance. Populations of C. maculatus were evolved for 20 and 25 generations under one of three dispersal regimens: completely free dispersal, limited dispersal, and no dispersal. There was no divergence among treatments in female reproductive tract scarring, ejaculate size, mating behaviour, fitness of experimental females mated to stock males, or fitness of stock females mated to experimental males. We suggest that this is likely due to insufficient strength of kin selection rather than a lack of genetic variation or time for selection. Limited dispersal alone is therefore not sufficient for kin selection to reduce male harmfulness in this species, consistent with general predictions that limited dispersal will only allow kin selection if local relatedness is independent of the intensity of competition among kin.

Methods
Data collected from the laboratory experiments described in the manuscript referred to. Analysed in R, according to the script provided.

性冲突的结局可受社会环境调控：雄性会对伤害行为对应的广义适合度（inclusive fitness）收益变化做出响应，且当雄性与熟悉的亲属竞争时，对雌性的伤害会更少。理论模型同样预测，若雄性的有限扩散能够可预测地提升局部亲缘关系水平，同时维持全局竞争，则亲缘选择可导致不同种群间雄性伤害行为的进化分化。然而，针对这些预测的实验检验却十分罕见。

我们在实验环境中评估了作为性冲突研究模式物种的绿豆象（Callosobruchus maculatus）雌雄个体的扩散速率。结果显示，雌性的扩散频率显著高于雄性，但扩散的雄性所移动的距离与雌性相当。随后，我们通过实验进化来检验限制扩散是否允许亲缘选择发挥作用，进而影响雄性伤害行为与雌性抗性的分化。我们将绿豆象种群置于三种扩散方案下分别进化20代与25代：完全自由扩散、有限扩散以及无扩散。各组在雌性生殖道疤痕形成、射精量、交配行为、与原种雄性交配的实验雌性适合度，以及与实验雄性交配的原种雌性适合度方面均未出现分化。我们认为这一结果很可能是由于亲缘选择的强度不足所致，而非缺乏遗传变异或选择所需的时间。因此，仅靠有限扩散并不足以让亲缘选择降低该物种的雄性伤害行为，这与一般性预测一致：即仅当局部亲缘关系与亲缘间竞争强度无关时，有限扩散才会允许亲缘选择发挥作用。

方法
数据来自手稿中描述的实验室实验，依照所提供的脚本在R语言中完成分析。