Data from: Sex-biased immunity is driven by relative differences in reproductive investment

Sex differences in immunity are often observed, with males generally having a weaker immune system than females. However, recent data in a sex-role-reversed species in which females compete to mate with males suggest that sexually competitive females have a weaker immune response. These findings support the hypothesis that sexual dimorphism in immunity has evolved in response to sex-specific fitness returns of investment in traits such as parental investment and longevity, but the scarcity of data in sex-reversed species prevents us from drawing general conclusions. Using an insect species in which males make a large but variable parental investment in their offspring, we use two indicators of immunocompetence to test the hypothesis that sex-biased immunity is determined by differences in parental investment. We found that when the value of paternal investment was experimentally increased, male immune investment became relatively greater than that of females. Thus, in this system, in which the direction of sexual competition is plastic, the direction of sex-biased immunity is also plastic and appears to track relative parental investment.免疫功能的性别差异屡被观测到，通常雄性的免疫系统相较于雌性更为薄弱。然而，针对性角色反转物种（sex-role-reversed species）的近期研究数据表明，在雌性需竞争以获取雄性配偶的这类物种中，具有性竞争行为的雌性其免疫应答反而更弱。上述发现支持了如下假说：免疫功能的性别二态性（sexual dimorphism）的演化，是为了响应特定性别的适合度回报——这类回报源自亲本投入（parental investment）、寿命等性状的投资；但由于性反转物种的相关研究数据稀缺，我们无法得出普适性结论。本研究选取了一种雄性会为后代提供大量且可变的亲本投入的昆虫物种，采用两项免疫能力（immunocompetence）指标来检验下述假说：免疫功能的性别偏向性由亲本投入的差异所决定。实验结果显示，当通过实验手段提升雄性亲本投入的价值后，雄性的免疫投入相对雌性而言变得更高。由此可见，在这一性竞争方向具有可塑性的研究体系中，免疫功能的性别偏向方向同样具备可塑性，且似乎与相对亲本投入水平相匹配。