From inter-group conflict to inter-group cooperation: insights from social insects

Philos Trans R Soc Lond B Biol Sci. 2022 May 23;377(1851):20210466. doi: 10.1098/rstb.2021.0466. Epub 2022 Apr 4.


The conflict between social groups is widespread, often imposing significant costs across multiple groups. The social insects make an ideal system for investigating inter-group relationships, because their interaction types span the full harming-helping continuum, from aggressive conflict, to mutual tolerance, to cooperation between spatially separate groups. Here we review inter-group conflict in the social insects and the various means by which they reduce the costs of conflict, including individual or colony-level avoidance, ritualistic behaviours and even group fusion. At the opposite extreme of the harming-helping continuum, social insect groups may peacefully exchange resources and thus cooperate between groups in a manner rare outside human societies. We discuss the role of population viscosity in favouring inter-group cooperation. We present a model encompassing intra- and inter-group interactions, and local and long-distance dispersal. We show that in this multi-level population structure, the increased likelihood of cooperative partners being kin is balanced by increased kin competition, such that neither cooperation (helping) nor conflict (harming) is favoured. This model provides a baseline context in which other intra- and inter-group processes act, tipping the balance toward or away from conflict. We discuss future directions for research into the ecological factors shaping the evolution of inter-group interactions. This article is part of the theme issue 'Intergroup conflict across taxa'.

Keywords: class-structure; inclusive fitness; intergroup conflict; intergroup cooperation; population viscosity; social insects.

Publication types

  • Review

MeSH terms

  • Aggression
  • Animals
  • Group Processes*
  • Humans
  • Insecta*