Within-group male relatedness reduces harm to females in Drosophila

To resolve the mechanisms that switch competition to cooperation is key to understanding biological organization. This is particularly relevant for intrasexual competition, which often leads to males harming females. Recent theory proposes that kin selection may modulate female harm by relaxing competition among male relatives. Here we experimentally manipulate the relatedness of groups of male Drosophila melanogaster competing over females to demonstrate that, as expected, within-group relatedness inhibits male competition and female harm. Females exposed to groups of three brothers unrelated to the female had higher lifetime reproductive success and slower reproductive ageing compared to females exposed to groups of three males unrelated to each other. Triplets of brothers also fought less with each other, courted females less intensively and lived longer than triplets of unrelated males. However, associations among brothers may be vulnerable to invasion by minorities of unrelated mal...

解析竞争转向合作的机制，是理解生物组织运作的核心课题。这一点与性内竞争（intrasexual competition）尤为相关——这类竞争往往会导致雄性对雌性造成伤害。现有理论提出，亲缘选择（kin selection）可通过缓解雄性亲属间的竞争，调节雄性对雌性的伤害行为。本研究通过实验操控以雌性为竞争资源的雄性黑腹果蝇（Drosophila melanogaster）种群的亲缘关系，验证了预期假设：种群内亲缘关系的提升会抑制雄性间的竞争以及对雌性的伤害。相较于暴露于3只互不相关雄性种群的雌性果蝇，暴露于3只同胞兄弟种群的雌性果蝇，其终身生殖成功率更高，生殖衰老进程也更为缓慢。相较于由互不相关雄性组成的三胞胎组，同胞兄弟组成的三胞胎组间打斗行为更少，对雌性的求偶强度更低，且个体寿命更长。不过，兄弟间的协作关联或许易受到少数非亲缘雄性的入侵……