Quantifying and comparing male harm between two Drosophila serrata lab populations

Male harm arises when traits that increase reproductive success in competition with other males also harm females as a side-effect. The extent of harm depends on male and female phenotypes, both of which can diverge between populations. Within a population, harm is inferred when increased exposure to males reduces female fitness, but studies of the divergence of male harm rarely manipulate male exposure. Here, we quantify male harm and compare its magnitude between two lab populations of Drosophila serrata that were derived from a common ancestor seven years earlier and subsequently held under conditions that minimized environmental differences. We manipulate female exposure to males in a factorial design involving all four combinations of males and females from these populations, providing insight into divergence in both sexes. Our results reveal substantial harm to females and provide stronger evidence of divergence in males than in females. Using these and other published data, we di..., We compared male harm and female resistance between the two popuations of Drosophila serrata (the '2006' and '2013' University of Ottawa populations). The experiment measured the fitness of 2006 and 2013 females when held under conditions of high or low exposure to 2006 or 2013 males. Exposure was manipulated by altering the frequency with which females were exposed to males (high = continuous exposure; low = 6h exposure every 3-4 days). All combinations of male exposure (high vs. low), male population (2006 vs. 2013), and female population (2006 vs. 2013) were performed, yielding a 2 × 2 × 2 factorial design involving eight unique combinations of treatment levels. The experiment was performed in two blocks over two consecutive generations of the populations during the summer of 2014, with 30 replicates of each of the eight treatment combinations within each block, yielding 480 replicates in total.A few individuals were lost due to experimental error, resulting in 463 replicates (averag..., Rows are replicates (i.e. single females). Female_Last.Alive and Female_First.Dead are the days at which the female was last observed alive and first observed dead, respectively, with fractional values denoting the approximate time of day that check was performed. Num_offspring columns give the number of offspring the female produced in a given vial (i.e. females were transferred to a new vail every 3-4 days). Zero values indicate that the female was alive at least some of the time while in that vial but produced no offspring, while missing values (\".\") indicate that that female was dead at that point. Total_Num_Offspring is simply the sum of all these values for a given female (i.e. replicate).雄性伤害是指在与其他雄性的竞争中提升繁殖成功率的性状，同时会附带对雌性造成伤害的现象。伤害的程度取决于雌雄两性的表型，而两性表型均可在不同种群间发生分化。在同一种群内，当雌性与雄性的接触增多导致其适合度下降时，即可推断存在雄性伤害；但针对雄性伤害分化的研究，极少会对雄性接触量进行操控。本研究对雄性伤害进行了量化，并比较了两个实验室种群的雄性伤害强度：这两个锯果蝇（Drosophila serrata）种群源自7年前的共同祖先，后续在尽可能控制环境差异最小化的条件下培养。我们采用析因设计操控雌性与雄性的接触量，涵盖了来自两个种群的雌雄个体的全部四种组合，以此解析两性的分化情况。研究结果显示雄性对雌性存在显著伤害，且相较于雌性，雄性的分化证据更为充分。借助本次及其他已发表的数据，我们[原文此处截断] 本研究比较了两个渥太华大学2006年与2013年建立的锯果蝇种群间的雄性伤害与雌性抗性水平。 本实验测定了2006年与2013年种群的雌性个体，在分别接触2006年或2013年种群雄性的高、低接触条件下的适合度。雄性接触量通过调整雌性与雄性的接触频率进行操控：高接触组为持续接触，低接触组为每3~4天接触6小时。本实验涵盖了雄性接触量（高vs低）、雄性种群（2006vs2013）、雌性种群（2006vs2013）的全部组合，形成了包含8种唯一处理水平组合的2×2×2析因设计。2014年夏季，实验分两个区组，在种群的两个连续世代中开展；每个区组内的8种处理组合各设置30次重复，总计480次重复。因实验误差损失了部分个体，最终有效重复数为463次（平均[原文此处截断]） 每行代表一次实验重复（即单个雌性个体）。字段Female_Last.Alive与Female_First.Dead分别表示雌性最后一次被观察到存活、首次被观察到死亡的天数，其中小数部分代表当日检查的大致时间。Num_offspring列记录雌性个体在指定饲养管中产生的后代数量（即雌性每3~4天会被转移至新的饲养管）。数值为0代表该雌性在对应饲养管饲养期间至少存活过一段时间，但未产生后代；缺失值（"."）代表该雌性在该时间点已死亡。Total_Num_Offspring为单个雌性（即单次重复）所有饲养管后代数量的总和。