Integrating cooperative breeding into theoretical concepts of cooperationIntroductionCooperationCooperation and the problem of outside optionsConcepts of cooperation and building blocksInvestment (a costly act)Return investment (a costly response)Direct or indirect interactionsPositive or negative control mechanismCategorising theories of cooperative breedingPay-to-stayGroup augmentationPrestigeDiscussionHow to study cooperative behaviour in cooperative breeders?New avenues for theoretical researchN-player cooperationOutside options: biological market theorySymmetric or asymmetric relationships and interactionsInteractions of kin based and non-kin based cooperationKinship, interdependence and the value of lasting associationsConclusionsAcknowledgementsReferencesBehavioural Processes 76 (2007) 61–72ReviewIntegrating cooperative breeding into theoretical concepts of cooperationRalph Bergm¨ullera,∗, Rufus A. Johnstoneb, Andrew F. Russellc, Redouan BsharyaaDepartment of Eco-Ethology, Institute of Biology, University of Neuchˆatel, Rue Emile Argand 11, CH-2009 Neuchˆatel, SwitzerlandbDepartment of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UKcDepartment of Animal & Plant Sciences, University of Sheffield, Sheffield S10 2TN, UKReceived 30 October 2006; accepted 16 November 2006AbstractIn cooperative breeding systems, some individuals help to raise offspring that are not their own. While early explanations for such altruisticbehaviour were predominantly based on kin selection, recent evidence suggests that direct benefits may be important in the maintenance ofcooperation. To date, however, discussions of cooperative breeding have made little reference to more general theories of cooperation betweenunrelated individuals (while these theories rarely address cooperative breeding). Here, we attempt to integrate the two fields. We identify four keyquestions that can be used to categorise different mechanisms for the maintenance of cooperative behaviour: (1) whether or not individuals investin others; (2) whether or not this initial investment elicits a return investment by the beneficiary; (3) whether the interaction is direct, i.e. betweentwo partners, or indirect (involving third parties) and (4) whether only actions that increase the fitness of the partner or also fitness reducing actions(punishment) are involved in the interaction. Asking these questions with regards to concepts in the literature on cooperative breeding, we found that(a) it is often straightforward to relate these concepts to general mechanisms of cooperation, but that (b) a single term (such as ‘pay-to-stay’, ‘groupaugmentation’ or ‘prestige’) may sometimes subsume two or more distinct mechanisms, and that (c) at least some mechanisms that are thought tobe important in cooperative breeding systems have remained largely unexplored in the theoretical literature on the evolution of cooperation. Futuretheoretical models should incorporate asymmetries in power and pay off structure caused for instance by dominance hierarchies or partner choice,and the use of N-player games. The key challenges for both theoreticians and empiricists will be to integrate the hitherto disparate fields and todisentangle the parallel effects of kin and non-kin based mechanisms of cooperation.© 2007 Published by Elsevier B.V.Keywords: Cooperative breeding; Evolution; Altruistic behaviour; Reciprocity; Pay-to-stay; Group augmentation; PrestigeContents1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 622. Cooperation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 632.1. Cooperation and the problem of outside options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643. Concepts of cooperation and building blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643.1. Investment (a costly act) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653.2. Return investment (a costly response) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653.3. Direct or indirect interactions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 663.4. Positive or negative control mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664. Categorising theories of cooperative breeding . . . . . . . . . . . . . . …