Data from: Reduced cellular immune response in social insect lineages

Social living poses challenges for individual fitness because of the increased risk of disease transmission among conspecifics. Despite this challenge, sociality is an evolutionarily successful lifestyle, occurring in the most abundant and diverse group of organisms on earth—the social insects. Two contrasting hypotheses predict the evolutionary consequences of sociality on immune systems. The social group hypothesis (SGH) posits that sociality leads to stronger individual immune systems because of the higher risk of disease transmission in social species. In contrast, the relaxed selection hypothesis (RSH) proposes that social species have evolved behavioral immune defenses that lower disease risk within the group, resulting in lower immunity at the individual level. We tested these hypotheses by measuring the encapsulation response in 11 eusocial and non-eusocial insect lineages. We build a phylogenetic mixed linear model to investigate the effect of behavior, colony size, and body size on cellular immune response. We found a significantly negative effect of colony size on immune function (P< 0.05). Our findings suggest that insects living in large societies may rely more on behavioral mechanisms, such as hygienic behaviors, than on immune function to reduce the risk of disease transmission among nestmates.