Parent–Offspring Conflict, Sibling Rivalry and Coadaptation


Conflict arises in families because of a fundamental relatedness asymmetry. When parents are equally related to all offspring they would prefer to divide resources equitably among young. However, offspring only share half of their genes with siblings. Thus each will be selected to demand the largest share of resources for itself, which conflicts with the interest of both parents and other siblings. Mathematical models have demonstrated that the resolution of this conflict depends on the degree to which parental provisioning and offspring solicitation influences resource allocation. Because levels of parental provisioning and offspring solicitation are affected by underlying genetic variation, they can evolve and coevolve, leading to coadapted parental and offspring traits. The Reactions Norms approach successfully captures both variation and consistency in parent and offspring strategies and is a promising tool for the investigation of family conflict.

Key Concepts:

  • Conflict exists within families, with offspring demanding more than parents are willing to provide, and each sibling desiring a larger share of resources than its littermates.

  • Both parents and offspring are able to influence provisioning, and their strategies are determined in part by genes.

  • How conflict is resolved depends on parental and offspring strategies; generally, the equilibrium point is somewhere between the parental and offspring optima.

  • Parental and offspring strategies coevolve to maximise inclusive fitness.

  • The Reaction Norms approach can be used to reconcile conflict and coadaptation.

Keywords: parent–offspring conflict; parent–offspring coadaptation; solicitation; provisioning; reaction norms

Figure 1.

Parent–offspring conflict over parental investment. The parent's optimum level of parental investment (P) lies at the point of maximal difference between benefits (B) and costs (C), which is shown by the upper diagonal line on the left. The offspring's optimum level of parental investment (O) lies at the point of maximal difference between benefits (B) and costs (C/2) which is shown by the lower diagonal line.

Figure 2.

Hypothetical Reaction Norms for provisioning and solicitation. Response curves for two parents (P1 and P2) and two offspring (O1 and O2) genotypes are shown. All possible equilibrium points are marked by black circles. Brown line and segment illustrate the crucial parameters describing the behaviour of individual P2, namely the elevation and slope of the curve.



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Further Reading

Davies NB, Krebs JR and West SA (2012) Parental Care and Family Conflicts in an Introduction to Behavioural Ecology. Oxford: Wiley Blackwell.

Wright J and Leonard ML (2002) The Evolution of Begging: Competition, Cooperation and Communication. Dordecht: Springer.

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Gini, Beatrice, and Hager, Reinmar(Oct 2014) Parent–Offspring Conflict, Sibling Rivalry and Coadaptation. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0003668.pub2]