Data from: Social context alters host behavior and infection risk

Variation in infection risk and transmission potential are widespread in human and wildlife diseases and play a central role in host-pathogen dynamics. To explain this variation, most studies focus on linking host traits to differences in pathogen exposure, infection, and transmission, but typically do not to account for hosts’ social context. Yet, an individual’s risk of acquiring infection is likely influenced jointly by their own traits and their social environment. Here, we use three natural genotypes of the fruit fly Drosophila melanogaster to test how variation in pathogen transmission is linked to differences in host behavior and social context. We constructed groups of 12 flies from one of three different genotypes and five different sex ratios (0%, 33%, 50%, 67%, or 100% female) in a fully factorial design. To each group we added a male or female “primary case” fly that had been exposed to the generalist fungal entomopathogen Metarhizium robertsii. We then recorded groups’ aggregation behavior, mating frequency, and infection prevalence. Aggregation and mating behavior were influences either jointly or additively by fly genotype and sex ratio. However, a combination of individual-level (mating history; the sex of the primary case) and group-level factors (sex ratio) jointly influenced individuals’ infection risk. There were more infections in female-biased groups, though the sex of the primary case also influenced sex-biased mortality and the relationship between individuals’ mating history and infection risk. Thus, an individual’s social environment can be an important predictor of social dynamics and their survival outcomes.宿主与野生动物疾病中，感染风险与传播潜力的变异普遍存在，且在宿主-病原体动态过程中发挥核心作用。为解释这类变异，多数研究聚焦于将宿主性状与病原体暴露、感染及传播的差异相关联，但通常未考量宿主的社会环境背景。然而，个体的感染风险大概率同时受自身性状与社会环境的共同影响。本研究以黑腹果蝇（Drosophila melanogaster）的3种自然基因型为实验材料，探究病原体传播变异与宿主行为、社会环境差异之间的关联。我们采用完全析因设计，构建了由3种基因型之一、以及5种不同性比（0%、33%、50%、67%或100%雌性）组合而成的12只果蝇群组。向每个群组中接入1只经广谱真菌昆虫病原真菌罗伯茨绿僵菌（Metarhizium robertsii）暴露处理的雄性或雌性“原发病例”果蝇。随后我们记录了各组的聚集行为、交配频率以及感染率。果蝇基因型与性比可通过联合效应或加性效应影响聚集与交配行为。但个体层面因素（交配史；原发病例的性别）与群体层面因素（性比）的组合，会共同影响个体的感染风险。雌性占比偏高的群组中感染发生率更高，不过原发病例的性别也会影响性偏向性死亡，以及个体交配史与感染风险之间的关联。由此可见，个体所处的社会环境可有效预测种群社会动态与个体存活结局。