Group Size and Social Conflict in Complex Societies

Abstract

Conflicts of interest over resources or reproduction among individuals in a social group have long been considered to result in automatic and universal costs to group living. However, exploring how social conflict varies with group size has produced mixed empirical results. Here we develop a model that generates alternative predictions for how social conflict should vary with group size depending on the type of benefits gained from being in a social group. We show that a positive relationship between social conflict and group size is favored when groups form primarily for the benefits of sociality but not when groups form mainly for accessing group-defended resources. Thus, increased social conflict in animal societies should not be viewed as an automatic cost of larger social groups. Instead, studying the relationship between social conflict and the types of grouping benefits will be crucial for understanding the evolution of complex societies. DisciplinesBehavior and Ethology | Biology | Demography, Population, and Ecology | Population Biology Submitted May 1, 2013; Accepted September 17, 2013; Electronically published December 10, 2013 abstract: Conflicts of interest over resources or reproduction among individuals in a social group have long been considered to result in automatic and universal costs to group living. However, exploring how social conflict varies with group size has produced mixed empirical results. Here we develop a model that generates alternative predictions for how social conflict should vary with group size depending on the type of benefits gained from being in a social group. We show that a positive relationship between social conflict and group size is favored when groups form primarily for the benefits of sociality but not when groups form mainly for accessing groupdefended resources. Thus, increased social conflict in animal societies should not be viewed as an automatic cost of larger social groups. Instead, studying the relationship between social conflict and the types of grouping benefits will be crucial for understanding the evolution of complex societies.

Negative association between parental care and sibling cooperation in earwigs: a new perspective on the early evolution of family life?

“…Cooperation is generally less likely to occur if competition between interacting individuals is high (Frank, ; West et al ., ). Accordingly, the incentive of offspring to share food should be inversely related to the severity of sibling competition, which in turn is classically assumed to increase with group size (Alexander, ; but see Shen et al ., ). Contrary to this prediction, our results showed that the level of sibling food transfer increased with group size.…”

“…To unravel the relation between parental care and sibling cooperation in earwig families, we measured the co‐expression of maternal food provisioning and sibling food transfer. Because group size can be an important parameter in family interactions that is classically assumed to affect the intensity of competition among group members (Alexander, ; Shen et al ., ) and has been linked to differences in mortality and developmental rates in European earwigs (Kölliker, ; Meunier & Kölliker, ), we first tested (1) whether group size (offspring number) shapes the expression of sibling food sharing and maternal food provisioning. We then investigated (2) the nature and direction of the potential association between the two types of food transfer.…”

Evolutionary dynamics of collective action in spatially structured populations

“…It is clear from the dependence of the critical cost-to-benefit ratios and the critical returns-to-scale parameters on group size (Table 2) that the effects of varying group sizes on the evolutionary dynamics of collective action will critically depend on the kind of good and its economies of scale. It would be interesting to integrate this phenomenon into our model, thus extending previous work on the effects of group size in the evolution of helping (Motro, 1991;Brännström et al, 2011;Peña, 2012;Shen et al, 2014).…”

Group size effects in social evolution

“…In this light, the analysis conducted here is also relevant to investigate group size effects in genetically structured populations, provided that the likely dependence of the inclusive gains from switching on group size is taken into account. Investigating the effects of group size on the evolution of cooperative behaviors under nontrivial population structure with the tools developed here would complement recent efforts in this area (Shen et al, 2014;Powers and Lehmann, 2017;Van Cleve, 2017).…”