Data from: Does kin selection moderate sexual conflict in Drosophila?

Two recent studies provide provocative experimental findings about the potential influence of kin recognition and cooperation on the level of sexual conflict in Drosophila melanogaster. In both studies, male fruit flies apparently curbed their mate-harming behaviours in the presence of a few familiar or related males, suggesting some form of cooperation mediated by kin selection. In one study, the reduction in agonistic behaviour by brothers apparently rendered them vulnerable to dramatic loss of paternity share when competing with an unrelated male. If these results are robust and generalizable, fruit flies could be a major new focus for the experimental study of kin selection and social evolution. In our opinion, however, the restrictive conditions required for male cooperation to be adaptive in this species make it unlikely to evolve. We investigated these phenomena in two different populations of D. melanogaster using protocols very similar to those in the two previous studies. Our experiments show no evidence for a reduction in mate harm based upon either relatedness or familiarity between males, and no reduction in male reproductive success when two brothers are in the presence of an unfamiliar, unrelated, ‘foreign’ male. Thus, the reduction of sexual conflict owing to male cooperation does not appear to be a general feature of the species, at least under domestication, and these contrasting results call for further investigation: in new populations, in the field and in the laboratory populations in which these phenomena have been reported.两项近期研究针对黑腹果蝇（Drosophila melanogaster）中亲缘识别（kin recognition）与合作（cooperation）对性冲突（sexual conflict）水平的潜在影响，提供了颇具启发性的实验发现。两项研究均显示，当存在少量熟悉或亲缘雄性时，雄性果蝇似乎会抑制其交配伤害行为（mate-harming behaviours），这暗示存在某种由亲缘选择（kin selection）介导的合作形式。其中一项研究发现，兄弟间攻击行为（agonistic behaviour）的减少，会使得它们在与无关雄性竞争时，面临父权份额（paternity share）大幅流失的风险。若上述结果具备稳健性且可推广，那么黑腹果蝇或将成为亲缘选择与社会演化实验研究的全新重要研究焦点。但我们认为，该物种中雄性合作若要具备适应性，所需的限制性条件使其演化可能性极低。我们采用与此前两项研究高度相似的实验方案，在两个不同的黑腹果蝇种群中对上述现象展开了探究。我们的实验未发现任何证据表明，基于雄性间亲缘关系或熟悉程度的交配伤害行为会有所减少；同时，当两只兄弟雄性与一只陌生且无亲缘关系的‘外来’雄性共存时，雄性的繁殖成功率（reproductive success）也未出现下降。因此，至少在实验室驯养种群中，由雄性合作介导的性冲突缓解现象，并非该物种的普遍特征；而这些相悖的研究结果，也呼吁在新种群、野外环境以及已报道该现象的实验室种群中开展进一步的探究。