Max Körner (Johannes Gutenberg University Mainz)
in: 'Frontiers in Ecology and Evolution': "The role of social and individual pathogen defense in an insect with facultative family life: insights into the early evolution of group living"
by Max Körner (Johannes Gutenberg University Mainz)
Sociality is a taxonomically widespread and successful, yet relatively rare phenomenon across the animal kingdom. This disparity is due to costs associated with group living, such as an increased risk of pathogen infection due to the increased density and/or relatedness in groups. Unlike solitary species, social species possess the unique capability of mounting collective immune defenses called social immunity, which has since been recognized as a key factor in maintaining obligatory and complex groups such as eusocial insects. However, recent studies revealed that social immunity also occurs in less derived, facultative forms of sociality, indicating that communal immune defenses may play an important role in the early evolution of sociality. As part of my PhD thesis, I investigated the occurrence and role of social immunity during the early family life of the European earwig Forficula auricularia, an insect exhibiting a primitive, facultative form of subsociality. Specifically, I was interested in whether social immunity occurs in this species, if such mechanisms are mediated by the caring mother, offspring, or both, and to what degree maternal presence and/or pathogen presence interact to shape short-term offspring gene expression and long-term immunocompetence. I found that F. auricularia families exhibited social immunity by producing feces with antimicrobial properties, and that this mechanism was largely independent of mother-offspring interactions. While maternal presence affected offspring’ immune gene expression changes in response to a pathogen, it had no long-term effect on offspring immunity. Overall, my results not only demonstrate the occurrence of social immunity in a species with primitive social life, but also that pathogen defenses in families are not exclusively driven by parents. These findings offer exciting new perspectives on the role of pathogen pressure as a potential driver, not inhibitor, of social evolution.