Importance of social immune system on the early evolution of social life

• Applicant: Professorin Dr. Susanne Foitzik, since 2/2016
• Subject Area: Evolution, Anthropology ; Sensory and Behavioural Biology ; Immunology
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 253852937

• Final Report Year: 2018

Final Report Abstract

The evolution of social life requires that group members develop efficient strategies to limit the risks of pathogen infection. These strategies generally involve both the individual and social immune systems, the latter being defined as any form of cooperation between group members that limits the risk of disease transmission. To date, social immunity has been mostly described in eusocial insects, e.g. ants, bees, wasps and termites. Although interesting, this strong focus makes unclear whether social immunity is a trait that has secondarily evolved in eusocial systems due to the strong pathogen pressure specifically expressed in these colonies, or whether it is a prerequisite for the evolution of complex forms of social life such as eusocial systems. The proposed project aimed at addressing this question using the European earwig, "Forficula auricularia", an insect with a simple and temporary family life. Our results first reveal that mothers do express forms of social immunity towards their eggs, but that they have no major effect on the immune defence of their newly hatched and adult offspring. Moreover, both juveniles and mothers keep their feces within the nest and the antimicrobial properties of these feces could serve as a form of social immunity. Interestingly, we showed that apparent forms of social immunity expressed among adults result from individual responses to a social stress, stressing the importance to use proper experimental design to shed light on patterns of social immunity. Overall, these results demonstrate that social immunity is an important, but not the sole component of defences against pathogens in species with simple social groups. This overall suggest that social immunity could be an ancestral parameter in the early evolution of social life, and thus provides novel insights into our general understanding of the link between pathogens and social evolution in insects.

Publications

• 2015. Feces production as a form of social immunity in an insect with facultative maternal care. BMC Evol. Biol. 15, 15:40
  Diehl, J.M., Körner, M., Pietsch, M., Meunier, J.
  
• 2015. Social immunity and the evolution of group living in insects. Philos. Trans. R. Soc. B Biol. Sci. 370, 20140102
  Meunier, J.
  
• 2016. Growing up with feces: benefits of allocoprophagy in families of the European earwig. Behav. Ecol. 27, 1775–1781
  Körner, M., Diehl, J.M., Meunier, J.
  
• 2017. Age, pathogen exposure, but not maternal care shape offspring immunity in an insect with facultative family life. BMC Evol. Biol. 17, 69
  Vogelweith, F., Körner, M., Foitzik, S., Meunier, J.
  
• 2017. Condition-dependent trade-off between weapon size and immunity in males of the European earwig. Sci. Rep. 7, 7988
  Körner, M., Vogelweith, F., Foitzik, S., Meunier, J.
  
• 2018. Extended winters entail long-term costs for insect offspring reared in an overwinter burrow. J. Therm. Biol. 74, 116–122
  Körner, M., Foitzik, S., Meunier, J.