UMD BIOL 608W - Despotic partner choice puts helpers under pressure

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Despotic partner choice puts helpers under pressure?Causes and consequences of power asymmetries between breeders and helpersGroup living as a form of cooperationHarassment, punishment and sanctioningReferencesBehavioural Processes 76 (2007) 120–125CommentaryDespotic partner choice puts helpers under pressure?Ronald No¨eEthologie des Primates, DEPE (IPHC CNRS UMR 7178), Universit´e Louis-Pasteur,23 rue Becquerel, Strasbourg 67087 Cedex, FranceReceived 8 January 2007; accepted 30 January 2007The authors of the target paper (Bergm¨uller et al., 2007) tryto bring order into the many forms ‘cooperation’ takes in thenatural world by designing a decision tree, most branches ofwhich have endpoints well known from the cooperation litera-ture. The advantage of this exercise is that it helps to classifynatural phenomena into the correct pigeonhole and relate it toother natural phenomena of the same class as well as to exist-ing theoretical considerations. The crucial assumption here isthat a relatively small number of pigeonholes suffices to clas-sify all observed cooperative phenomena. Otherwise, one hasto create ever-smaller branches or accept that many phenomenaget stuck between branches. For example, where do we clas-sify the behaviour of a helper, who gains direct benefits throughgroup augmentation (pseudo-reciprocity) plus indirect benefitsthrough increased reputation (indirect reciprocity) and inclusivefitness?One reason the tree presented in the target paper remains moreor less orderly is that the authors have left out some importantmechanisms, such as partner choice in general (see p. 14 of theMs) and competitive altruism in particular (Barclay and Willer,2007; Roberts, 1998), as well as restricted themselves to coop-erative breeding. My impression is that the tree would becomerather bushy without those restrictions and that we will run out ofterms at some point. Pigeonholing can be very useful in orderingour thoughts about phenomena. The risk is that we artificiallysplit up what is conceptually in fact identical or comparable. Inmy recent review for Animal Behaviour (No¨e, 2006) I went theopposite direction and proposed to concentrate on two essen-tial parameters: cooperative investment and cooperative returns.Both can come in many disguises, such as reproduction, pro-tection, food, reputation, etc. and can be measured in relativefitness or in proximate currencies, such as risk of injury or gainsand losses in time and energy. The puzzle then reduces to iden-tifying the factors that determine the values of investments andE-mail address: [email protected]. Examples of such factors are the difference betweenparticipants in physical force or in the number of alternativeoptions each has; the degree of kinship between them; the timelag between interactions, etc. In essence the question is whatdetermines the amount of control each participant has over theinvestment (s)he makes and the returns (s)he obtains. The draw-back of my approach is that one cannot always easily make theconnection to existing theoretical considerations. Not that this isalways a big loss, since some theoretical considerations out therelack all connection to empirical facts anyway. The advantage isthat one can go down straight to the business of measuring andanalysing the essentials in the particular system at hand ratherthan worrying over the correct label.My more direct comments to issues brought up by Bergm¨ulleret al.’s target paper concern the following themes:(1) The causes and consequences of power asymmetriesbetween breeders and helpers.(2) Sociality as a cooperative investment.(3) The distinctions between three related phenomena: harass-ment, punishment and sanctioning.1. Causes and consequences of power asymmetriesbetween breeders and helpersBergm¨uller et al. (2007) chose not to include partner choiceas one of the discriminating factors in their decision tree (p.14 in the Ms). I assert, however, that this makes the exercisefutile, because no helper system with more than one helper canbe understood without considering the consequences of partnerchoice. Through partner choice breeders can in principle playoff their own offspring and other underlings against each other.This changes the power balance and thus the investments doneby both parties.In my explanation I largely repeat a story published quite awhile ago (No¨e et al., 1991). I restrict myself here to a verbalargument based on a situation in which there is one breeding pair0376-6357/$ – see front matter © 2007 Elsevier B.V. All rights reserved.doi:10.1016/j.beproc.2007.01.015R. No¨e / Behavioural Processes 76 (2007) 120–125 121with two or more helpers that are unrelated to them. The mainconsequences of excluding kinship effects are that (a) the breed-ers have no interest in the reproductive success of the helpers,neither as dispersers nor as heirs of their breeding positions and(b) the helpers do not increase their inclusive fitness by helping.I further assume that (1) Helpers can provide benefits to breed-ers in only two forms: provisioning of the young and increasingsafety (dilution; early warning, etc.). (2) Helpers benefit throughthe safety of group living and access to the resources in thegroup’s territory. I ignore eventual future benefits returned bythe offspring the helpers care for, because it is difficult to seehow helpers could control reimbursements in this form. Note,however, that examples of such ‘delayed reciprocity’ have beenreported (Ligon and Ligon, 1978, 1983). (3) The breeders aredominant over all other group members and present a commonfront, i.e. I ignore eventual conflicts of interest between breed-ers. I will use the term ‘subordinate’ for all adults other thanthe breeders in a cooperatively breeding group and the term‘helper’ only for those subordinates that provision the breeders’offspring.The following questions can then be asked:• Can and do breeders force helpers to help more than theywould do voluntarily?I consider it very unlikely that a cooperative breeding groupis without conflicts of interests and assume the most likelysituation here, namely that helpers tend to help less than isoptimal from the point of view of the breeder. A tell-talesign of a power asymmetry between breeders and helpersis that breeders reduce their own effort more when there aremore helpers (for a classical example see Brown et al., 1978).This assumption of a power asymmetry is the basis of


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