Intra-group relatedness affects parental and helper investment rules in offspring care
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In any system where multiple individuals jointly contribute to rearing offspring, conflict is expected to arise over the relative contributions of each carer. Existing theoretical work on the conflict over care has: (a) rarely considered the influence of tactical investment during offspring production on later contributions to offspring rearing; (b) concentrated mainly on biparental care, rather than cooperatively caring groups comprising both parents and helpers; and (c) typically ignored relatedness between carers as a potential influence on investment behavior. We use a game-theoretical approach to explore the effects of female production tactics and differing group relatedness structures on the expected rearing investment contributed by breeding females, breeding males, and helpers in cooperative groups. Our results suggest that the breeding female should pay higher costs overall when helpful helpers are present, as she produces additional offspring to take advantage of the available care. We find that helpers related to offspring through the breeding female rather than the breeding male should contribute less to care, and decrease their contribution as group size increases, because the female refrains from producing additional offspring to exploit them. Finally, within-group variation in helper relatedness also affects individual helper investment rules by inflating the differences between the contributions to care of dissimilar helpers. Our findings underline the importance of considering maternal investment decisions during offspring production to understand investment across the entire breeding attempt, and provide empirically testable predictions concerning the interplay between maternal, paternal and helper investment and how these are modified by different relatedness structures.
KeywordsBiparental care Cooperative breeding Game theory Load lightening Maternal effects Provisioning rules
This work was supported by a Natural Environment Research Council Studentship to the University of Cambridge (J.L.S.) and by a Royal Society University Research Fellowship (A.F.R.). We are grateful to two anonymous reviewers for helpful suggestions.
- Houston AI, Davies NB (1985) The evolution of cooperation and life history in the dunnock, Prunella modularis. In: Sibly RM, Smith RH (eds) Behavioural ecology: ecological consequences of adaptive behaviour. Blackwell Scientific Publications, Oxford, pp 471–487Google Scholar
- Kokko H, Johnstone RA, Clutton-Brock TH (2001) The evolution of cooperative breeding through group augmentation. Proc R Soc Lond B 268:187–196Google Scholar
- Lessells C, McNamara JM (2012) Sexual conflict over parental investment in repeated bouts: negotiation reduces overall care. Proc R Soc Lond B 279:1506–1514Google Scholar
- Stacey PB, Koenig WD (eds) (1990) Cooperative breeding in birds: long-term studies of ecology and behavior. Cambridge University Press, CambridgeGoogle Scholar
- Stearns SC (1992) The evolution of life histories. Oxford University Press, OxfordGoogle Scholar
- Trivers RL (1974) Parent–offspring conflict. Am Zool 14:249–264Google Scholar