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Benvenuto C, Lorenzi MC. Social regulation of reproduction: control or signal? Trends Ecol Evol 2023; 38:1028-1040. [PMID: 37385846 DOI: 10.1016/j.tree.2023.05.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 05/12/2023] [Accepted: 05/12/2023] [Indexed: 07/01/2023]
Abstract
Traditionally, dominant breeders have been considered to be able to control the reproduction of other individuals in multimember groups that have high variance in reproductive success/reproductive skew (e.g., forced sterility/coercion of conspecifics in eusocial animals; sex-change suppression in sequential hermaphrodites). These actions are typically presented as active impositions by reproductively dominant individuals. However, how can individuals regulate the reproductive physiology of others? Alternatively, all contestants make reproductive decisions, and less successful individuals self-downregulate reproduction in the presence of dominant breeders. Shifting perspective from a top-down manipulation to a broader view, which includes all contenders, and using a multitaxon approach, we propose a unifying framework for the resolution of reproductive skew conflicts based on signalling rather than control, along a continuum of levels of strategic regulation of reproduction.
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Affiliation(s)
- Chiara Benvenuto
- School of Science, Engineering, and Environment, University of Salford, Salford, UK.
| | - Maria Cristina Lorenzi
- Laboratoire d'Ethologie Expérimentale et Comparée (LEEC), Université Sorbonne Paris Nord, Villetaneuse, France
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2
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Crowley PH, Tentelier C. Polyandry as a Male Strategy? A Game Between Aggressive and Tolerant Males, Arbitrated by Females. Am Nat 2021; 199:345-361. [DOI: 10.1086/718028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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3
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Liu M, West SA, Cooper GA. Relatedness and the evolution of mechanisms to divide labor in microorganisms. Ecol Evol 2021; 11:14475-14489. [PMID: 34765120 PMCID: PMC8571581 DOI: 10.1002/ece3.8067] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Accepted: 08/16/2021] [Indexed: 01/08/2023] Open
Abstract
Division of labor occurs when cooperating individuals specialize to perform different tasks. In bacteria and other microorganisms, some species divide labor by random specialization, where an individual's role is determined by random fluctuations in biochemical reactions within the cell. Other species divide labor by coordinating across individuals to determine which cells will perform which task, using mechanisms such as between-cell signaling. However, previous theory, examining the evolution of mechanisms to divide labor between reproductives and sterile helpers, has only considered clonal populations, where there is no potential for conflict between individuals. We used a mixture of analytical and simulation models to examine nonclonal populations and found that: (a) intermediate levels of coordination can be favored, between the extreme of no coordination (random) and full coordination; (b) as relatedness decreases, coordinated division of labor is less likely to be favored. Our results can help explain why coordinated division of labor is relatively rare in bacteria, where groups may frequently be nonclonal.
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Affiliation(s)
- Ming Liu
- Department of ZoologyUniversity of OxfordOxfordUK
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4
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Yip EC, Smith DR, Lubin Y. Long-Term Colony Dynamics and Fitness in a Colonial Tent-Web Spider Cyrtophora citricola. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.725647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Social animals are expected to experience a positive effect of conspecific number or density on fitness (an Allee effect) because of the benefits of group living. However, social animals also often disperse to live either solitarily or in small groups, so to understand why social animals leave their groups it is necessary to understand how group size affects both average fitness and the expected fitness outcomes of individuals. We examined the relationships between group size and fitness in the colonial spider Cyrtophora citricola using long-term observations of colony demographics. We censused colonies, recording the number of juveniles, large females, and egg sacs, approximately every 2 months for 2 years. We also recorded the substrates supporting colony webs, including plant species and size, and the azimuth the colony occupied on the plant. Colonies in all regions showed cyclical patterns of growth and decline; however, regions were not synchronized, and seasonal effects differed between years. Colonies with fewer individuals at the initial observation were less likely to survive over the course of observations, and extinction rates were also influenced by an interaction between region and plant substrate. Small colonies were more likely to be extinct by the next census, but if they survived, they were more likely to have high growth rates compared to larger colonies. Despite the potential for high growth rates, high extinction rates depressed the average fitness of small colonies so that population growth rates peaked at intermediate colony sizes. Variance in egg sac production also peaked at intermediate colony sizes, suggesting that competitive interactions may increase the uneven distribution of resources in larger groups. Even if average fitness is high, if spiders can anticipate poor outcomes in large colonies, they may disperse to live solitarily or in smaller, less competitive groups.
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5
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Wilson KM, Codding BF. The Marginal Utility of Inequality : A Global Examination across Ethnographic Societies. HUMAN NATURE-AN INTERDISCIPLINARY BIOSOCIAL PERSPECTIVE 2021; 31:361-386. [PMID: 33523386 DOI: 10.1007/s12110-020-09383-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/15/2020] [Indexed: 11/30/2022]
Abstract
Despite decades of research, we still lack a clear explanation for the emergence and persistence of inequality. Here we propose and evaluate a marginal utility of inequality hypothesis that nominates circumscription and environmental heterogeneity as independent, necessary conditions for the emergence of intragroup material inequality. After coupling the Standard Cross-Cultural Sample (SCCS) with newly generated data from remote sensing, we test predictions derived from this hypothesis using a multivariate generalized additive model that accounts for spatial and historical dependence as well as subsistence mode. Our analyses show that the probability a society will be stratified increases significantly as a function of proxies of environmental heterogeneity and environmental circumscription. This supports the hypothesis that increasing environmental heterogeneity and circumscription drives the emergence and persistence of inequality among documented societies across the globe. We demonstrate how environmental heterogeneity and circumscription produce situations that limit individuals' options so that some may find it in their best interest to give up some autonomy for material gain, while others may find it in their best interest to give up some material resources for another individual's time or deference. These results support the marginal utility of inequality framework and enable future explorations of the ecological conditions that facilitate the emergence of intragroup inequality through time and across the globe.
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Affiliation(s)
- Kurt M Wilson
- Department of Anthropology, University of Utah, 260 S. Central Campus Drive, Room 4625, Salt Lake City, UT, 84112, USA.
| | - Brian F Codding
- Department of Anthropology, University of Utah, 260 S. Central Campus Drive, Room 4625, Salt Lake City, UT, 84112, USA
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6
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Barclay P, Benard S. The effects of social vs. asocial threats on group cooperation and manipulation of perceived threats. EVOLUTIONARY HUMAN SCIENCES 2020; 2:e54. [PMID: 37588340 PMCID: PMC10427451 DOI: 10.1017/ehs.2020.48] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Individuals benefit from maintaining the well-being of their social groups and helping their groups to survive threats such as intergroup competition, harsh environments and epidemics. Correspondingly, much research shows that groups cooperate more when competing against other groups. However, 'social' threats (i.e. outgroups) should elicit stronger cooperation than 'asocial' threats (e.g. environments, diseases) because (a) social losses involve a competitor's gain and (b) a strong cooperative reaction to defend the group may deter future outgroup threats. We tested this prediction in a multiround public goods game where groups faced periodic risks of failure (i.e. loss of earnings) which could be overcome by sufficient cooperation. This threat of failure was framed as either a social threat (intergroup competition) or an asocial threat (harsh environment). We find that cooperation was higher in response to social threats than asocial threats. We also examined participants' willingness to manipulate apparent threats to the group: participants raised the perceived threat level similarly for social and asocial threats, but high-ranking participants increased the appearance of social threats more than low-ranking participants did. These results show that people treat social threats differently than asocial threats, and support previous work on leaders' willingness to manipulate perceived threats.
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Affiliation(s)
- Pat Barclay
- Department of Psychology, University of Guelph, 50 Stone Rd. E., Guelph, N1G 2W1, ON, Canada
| | - Stephen Benard
- Department of Sociology, Indiana University, Ballantine Hall, 1020 E. Kirkland Ave, Bloomington, 47405, IN, USA
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7
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Barbasch TA, Alonzo SH, Buston PM. Power and punishment influence negotiations over parental care. Behav Ecol 2020. [DOI: 10.1093/beheco/araa034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Asymmetries in power (the ability to influence the outcome of conflict) are ubiquitous in social interactions because interacting individuals are rarely identical. It is well documented that asymmetries in power influence the outcome of reproductive conflict in social groups. Yet power asymmetries have received little attention in the context of negotiations between caring parents, which is surprising given that parents are often markedly different in size. Here we built on an existing negotiation model to examine how power and punishment influence negotiations over care. We incorporated power asymmetry by allowing the more-powerful parent, rank 1, to inflict punishment on the less-powerful parent, rank 2. We then determined when punishment will be favored by selection and how it would affect the negotiated behavioral response of each parent. We found that with power and punishment, a reduction in one parent’s effort results in partial compensation by the other parent. However, the degree of compensation is asymmetric: the rank 2 compensates more than the rank 1. As a result, the fitness of rank 1 increases and the fitness of rank 2 decreases, relative to the original negotiation model. Furthermore, because power and punishment enable one parent to extract greater effort from the other, offspring can do better, that is, receive more total effort, when there is power and punishment involved in negotiations over care. These results reveal how power and punishment alter the outcome of conflict between parents and affect offspring, providing insights into the evolutionary consequences of exerting power in negotiations.
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Affiliation(s)
- Tina A Barbasch
- Department of Biology and Marine Program, Boston University, Boston, MA, USA
| | - Suzanne H Alonzo
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA USA
| | - Peter M Buston
- Department of Biology and Marine Program, Boston University, Boston, MA, USA
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8
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Sheehan MJ, Reeve HK. Evolutionarily stable investments in recognition systems explain patterns of discrimination failure and success. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190465. [PMID: 32420853 DOI: 10.1098/rstb.2019.0465] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Many animals are able to perform recognition feats that astound us-such as a rodent recognizing kin it has never met. Yet in other contexts, animals appear clueless as when reed warblers rear cuckoo chicks that bear no resemblance to their own species. Failures of recognition when it would seem adaptive have been especially puzzling. Here, we present a simple tug-of-war game theory model examining how individuals should optimally invest in affecting the accuracy of discrimination between desirable and undesirable recipients. In the game, discriminating individuals (operators) and desirable and undesirable recipients (targets and mimics, respectively) can all invest effort into their own preferred outcome. We demonstrate that stable inaccurate recognition will arise when undesirable recipients have large fitness gains from inaccurate recognition relative to the pay-offs that the other two parties receive from accurate recognition. The probability of accurate recognition is often determined by just the relative pay-offs to the desirable and undesirable recipients, rather than to the discriminator. Our results provide a new lens on long-standing puzzles including a lack of nepotism in social insect colonies, tolerance of brood parasites and male birds caring for extra-pair young in their nests, which our model suggests should often lack accurate discrimination. This article is part of the theme issue 'Signal detection theory in recognition systems: from evolving models to experimental tests'.
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Affiliation(s)
- Michael J Sheehan
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
| | - H Kern Reeve
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
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9
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Nonacs P. Reproductive skew in cooperative breeding: Environmental variability, antagonistic selection, choice, and control. Ecol Evol 2019; 9:10163-10175. [PMID: 31624543 PMCID: PMC6787806 DOI: 10.1002/ece3.5502] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 07/02/2019] [Accepted: 07/05/2019] [Indexed: 01/05/2023] Open
Abstract
A multitude of factors may determine reproductive skew among cooperative breeders. One explanation, derived from inclusive fitness theory, is that groups can partition reproduction such that subordinates do at least as well as noncooperative solitary individuals. The majority of recent data, however, fails to support this prediction; possibly because inclusive fitness models cannot easily incorporate multiple factors simultaneously to predict skew. Notable omissions are antagonistic selection (across generations, genes will be in both dominant and subordinate bodies), constraints on the number of sites suitable for successful reproduction, choice in which group an individual might join, and within-group control or suppression of competition. All of these factors and more are explored through agent-based evolutionary simulations. The results suggest the primary drivers for the initial evolution of cooperative breeding may be a combination of limited suitable sites, choice across those sites, and parental manipulation of offspring into helping roles. Antagonistic selection may be important when subordinates are more frequent than dominants. Kinship matters, but its main effect may be in offspring being available for manipulation while unrelated individuals are not. The greater flexibility of evolutionary simulations allows the incorporation of species-specific life histories and ecological constraints to better predict sociobiology.
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Affiliation(s)
- Peter Nonacs
- Department of Ecology and Evolutionary BiologyUniversity of CaliforniaLos AngelesCAUSA
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10
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Port M, Schülke O, Ostner J. Reproductive tolerance in male primates: Old paradigms and new evidence. Evol Anthropol 2018; 27:107-120. [PMID: 29971904 DOI: 10.1002/evan.21586] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 03/02/2018] [Accepted: 04/04/2018] [Indexed: 02/06/2023]
Abstract
Within social groups of primates, males commonly compete over reproduction, but they may also rely on cooperation with other males. Theory suggests that it may be adaptive for male primates to tolerate some reproduction by other males if reproductive tolerance fosters cooperation, particularly that dominant males yield so-called reproductive concessions to subordinates to entice their cooperation. We review four recent studies that claimed to have found evidence for reproductive concessions or similar forms of reproductive tolerance. However, upon critical reevaluation of their results, no study provides conclusive support for reproductive concessions as predicted by theoretical models. Yet two studies demonstrated a form of reproductive tolerance that cannot be explained by any of the existing models, and that seems to have evolved only in multi-male, multi-female societies with diverse strategic options for males. Our article provides guidance how to study this form of reproductive tolerance in the absence of a unifying model.
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Affiliation(s)
- Markus Port
- Department of Behavioral Ecology, Georg-August-University Göttingen, Göttingen, Germany
| | - Oliver Schülke
- Department of Behavioral Ecology, Georg-August-University Göttingen, Göttingen, Germany.,Research Group Primate Social Evolution, German Primate Centre, Leibniz Institute for Primate Research, Göttingen, Germany
| | - Julia Ostner
- Department of Behavioral Ecology, Georg-August-University Göttingen, Göttingen, Germany.,Research Group Primate Social Evolution, German Primate Centre, Leibniz Institute for Primate Research, Göttingen, Germany
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11
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Stress levels of dominants reflect underlying conflicts with subordinates in a cooperatively breeding species. Behav Ecol Sociobiol 2018. [DOI: 10.1007/s00265-018-2484-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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12
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Barker JL, Bronstein JL, Friesen ML, Jones EI, Reeve HK, Zink AG, Frederickson ME. Synthesizing perspectives on the evolution of cooperation within and between species. Evolution 2017; 71:814-825. [PMID: 28071790 DOI: 10.1111/evo.13174] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 12/24/2016] [Accepted: 01/04/2017] [Indexed: 12/11/2022]
Abstract
Cooperation is widespread both within and between species, but are intraspecific and interspecific cooperation fundamentally similar or qualitatively different phenomena? This review evaluates this question, necessary for a general understanding of the evolution of cooperation. First, we outline three advantages of cooperation relative to noncooperation (acquisition of otherwise inaccessible goods and services, more efficient acquisition of resources, and buffering against variability), and predict when individuals should cooperate with a conspecific versus a heterospecific partner to obtain these advantages. Second, we highlight five axes along which heterospecific and conspecific partners may differ: relatedness and fitness feedbacks, competition and resource use, resource-generation abilities, relative evolutionary rates, and asymmetric strategy sets and outside options. Along all of these axes, certain asymmetries between partners are more common in, but not exclusive to, cooperation between species, especially complementary resource use and production. We conclude that cooperation within and between species share many fundamental qualities, and that differences between the two systems are explained by the various asymmetries between partners. Consideration of the parallels between intra- and interspecific cooperation facilitates application of well-studied topics in one system to the other, such as direct benefits within species and kin-selected cooperation between species, generating promising directions for future research.
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Affiliation(s)
- Jessica L Barker
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, 85721.,Current Address: Aarhus Institute of Advanced Studies, Aarhus University, 8000, Aarhus C, Denmark
| | - Judith L Bronstein
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, 85721
| | - Maren L Friesen
- Department of Plant Biology, Michigan State University, East Lansing, Michigan, 48824
| | - Emily I Jones
- Department of BioSciences, Rice University, Houston, Texas, 77005
| | - H Kern Reeve
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York, 14853
| | - Andrew G Zink
- Department of Biology, San Francisco State University, San Francisco, California, 94132
| | - Megan E Frederickson
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
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13
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Andrade ACR, Miranda EA, Del Lama MA, Nascimento FS. Reproductive concessions between related and unrelated members promote eusociality in bees. Sci Rep 2016; 6:26635. [PMID: 27211350 PMCID: PMC4876382 DOI: 10.1038/srep26635] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 05/06/2016] [Indexed: 11/24/2022] Open
Abstract
Animal societies exhibit remarkable variation in their breeding strategies. Individuals can maximize their fitness by either reproducing or by helping relatives. Social hymenopterans have been key taxa for the study of Hamilton’s inclusive fitness theory because the haplodiploid sex-determination system results in asymmetric relatedness among breeders producing conflict over the partitioning of reproduction. In small cooperative groups of insects, totipotent individuals may maximize their inclusive fitness by controlling reproduction despotically rather than helping their relatives. Here, we demonstrate that the dominant females of the primitively eusocial bee Euglossa melanotricha (Apidae: Euglossini) control reproduction, but concede part of the reproductive output with their related and unrelated subordinates. As expected, a dominant female capitalizes on the direct reproduction of related subordinates, according to her interests. We found that reproductive skew was positively correlated with relatedness. The concessions were highly reduced in mother-daughter and sibling nests (relatedness r ± s.d. = 0.54 ± 0.02 and 0.79 ± 0.02, respectively) but much more egalitarian in unrelated associations (r = −0.10 ± 0.01). We concluded that reproductive skew in these primitively eusocial bees is strongly related to the genetic structure of associations, and also that females are able to assess pairwise relatedness, either directly or indirectly, and use this information to mediate social contracts.
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Affiliation(s)
- Aline C R Andrade
- Laboratório de Comportamento e Ecologia de Insetos Sociais - Departamento de Biologia - FFCLRP - Universidade de São Paulo - Av. Bandeirantes, 3900, Ribeirão Preto - SP, Brasil
| | - Elder A Miranda
- Laboratório de Genética Evolutiva de Himenópteros, Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, Brasil
| | - Marco A Del Lama
- Laboratório de Genética Evolutiva de Himenópteros, Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, Brasil
| | - Fábio S Nascimento
- Laboratório de Comportamento e Ecologia de Insetos Sociais - Departamento de Biologia - FFCLRP - Universidade de São Paulo - Av. Bandeirantes, 3900, Ribeirão Preto - SP, Brasil
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14
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Zink AG, Lyon BE. Evolution of Conspecific Brood Parasitism versus Cooperative Breeding as Alternative Reproductive Tactics. Am Nat 2016; 187:35-47. [DOI: 10.1086/684127] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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15
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Moya C, Sear R. Intergenerational conflicts may help explain parental absence effects on reproductive timing: a model of age at first birth in humans. PeerJ 2014; 2:e512. [PMID: 25165627 PMCID: PMC4137655 DOI: 10.7717/peerj.512] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 07/22/2014] [Indexed: 12/05/2022] Open
Abstract
Background. Parental absences in childhood are often associated with accelerated reproductive maturity in humans. These results are counterintuitive for evolutionary social scientists because reductions in parental investment should be detrimental for offspring, but earlier reproduction is generally associated with higher fitness. In this paper we discuss a neglected hypothesis that early reproduction is often associated with parental absence because it decreases the average relatedness of a developing child to her future siblings. Family members often help each other reproduce, meaning that parents and offspring may find themselves in competition over reproductive opportunities. In these intergenerational negotiations offspring will have less incentive to help the remaining parent rear future half-siblings relative to beginning reproduction themselves. Method. We illustrate this “intergenerational conflict hypothesis” with a formal game-theoretic model. Results. We show that when resources constrain reproductive opportunities within the family, parents will generally win reproductive conflicts with their offspring, i.e., they will produce more children of their own and therefore delay existing offsprings’ reproduction. This is due to the asymmetric relatedness between grandparents and grandchildren (r = .25), compared to siblings (r = 0.5), resulting in greater incentives for older siblings to help rear younger siblings than for grandparents to help rear grandchildren. However, if a parent loses or replaces their partner, the conflict between the parent and offspring becomes symmetric since half siblings are as related to one another as grandparents are to grandchildren. This means that the offspring stand to gain more from earlier reproduction when their remaining parent would produce half, rather than full, siblings. We further show that if parents senesce in a way that decreases the quality of their infant relative to their offspring’s infant, the intergenerational conflict can shift to favor the younger generation.
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Affiliation(s)
- Cristina Moya
- Department of Population Health, London School of Hygiene and Tropical Medicine , London , United Kingdom
| | - Rebecca Sear
- Department of Population Health, London School of Hygiene and Tropical Medicine , London , United Kingdom
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16
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Suppressing subordinate reproduction provides benefits to dominants in cooperative societies of meerkats. Nat Commun 2014; 5:4499. [PMID: 25047446 PMCID: PMC4109011 DOI: 10.1038/ncomms5499] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Accepted: 06/25/2014] [Indexed: 11/08/2022] Open
Abstract
In many animal societies, a small proportion of dominant females monopolize reproduction by actively suppressing subordinates. Theory assumes that this is because subordinate reproduction depresses the fitness of dominants, yet the effect of subordinate reproduction on dominant behaviour and reproductive success has never been directly assessed. Here, we describe the consequences of experimentally preventing subordinate breeding in 12 groups of wild meerkats (Suricata suricatta) for three breeding attempts, using contraceptive injections. When subordinates are prevented from breeding, dominants are less aggressive towards subordinates and evict them less often, leading to a higher ratio of helpers to dependent pups, and increased provisioning of the dominant's pups by subordinate females. When subordinate breeding is suppressed, dominants also show improved foraging efficiency, gain more weight during pregnancy and produce heavier pups, which grow faster. These results confirm the benefits of suppression to dominants, and help explain the evolution of singular breeding in vertebrate societies.
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17
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Port M, Cant MA. Reproductive Competition Among Males in Multimale Groups of Primates: Modeling the Costs and Effectiveness of Conflict. INT J PRIMATOL 2013. [DOI: 10.1007/s10764-013-9744-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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18
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Barclay P, Benard S. Who cries wolf, and when? Manipulation of perceived threats to preserve rank in cooperative groups. PLoS One 2013; 8:e73863. [PMID: 24069239 PMCID: PMC3772075 DOI: 10.1371/journal.pone.0073863] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2012] [Accepted: 07/26/2013] [Indexed: 11/24/2022] Open
Abstract
People perform greater within-group cooperation when their groups face external threats, such as hostile outgroups or natural disasters. Researchers and social commentators suggest that high-ranking group members manipulate this "threat-dependent" cooperation by exaggerating threats in order to promote cooperation and suppress competition for their position. However, little systematic research tests this claim or possible situational moderators. In three studies, we use a cooperative group game to show that participants pay to increase others' perceptions of group threats, and spend more on manipulation when holding privileged positions. This manipulation cost-effectively elicits cooperation and sustains privilege, and is fostered by competition over position, not only position per se. Less cooperative people do more manipulation than more cooperative people do. Furthermore, these effects generalize to broader definitions of privilege. Conceptually, these results offer new insights into an understudied dimension of group behavior. Methodologically, the research extends cooperative group games to allow for analyzing more complex group dynamics.
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Affiliation(s)
- Pat Barclay
- Department of Psychology, University of Guelph, Guelph, Ontario, Canada
| | - Stephen Benard
- Department of Sociology, Indiana University, Bloomington, Indiana, United States of America
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19
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20
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Nelson-Flower MJ, Hockey PAR, O'Ryan C, English S, Thompson AM, Bradley K, Rose R, Ridley AR. Costly reproductive competition between females in a monogamous cooperatively breeding bird. Proc Biol Sci 2013; 280:20130728. [PMID: 23677348 DOI: 10.1098/rspb.2013.0728] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In many cooperatively breeding societies, only a few socially dominant individuals in a group breed, reproductive skew is high, and reproductive conflict is common. Surprisingly, the effects of this conflict on dominant reproductive success in vertebrate societies have rarely been investigated, especially in high-skew societies. We examine how subordinate female competition for breeding opportunities affects the reproductive success of dominant females in a monogamous cooperatively breeding bird, the Southern pied babbler (Turdoides bicolor). In this species, successful subordinate reproduction is very rare, despite the fact that groups commonly contain sexually mature female subordinates that could mate with unrelated group males. However, we show that subordinate females compete with dominant females to breed, and do so far more often than expected, based on the infrequency of their success. Attempts by subordinates to obtain a share of breeding impose significant costs on dominant females: chicks fledge from fewer nests, more nests are abandoned before incubation begins, and more eggs are lost. Dominant females appear to attempt to reduce these costs by aggressively suppressing potentially competitive subordinate females. This empirical evidence provides rare insight into the nature of the conflicts between females and the resultant costs to reproductive success in cooperatively breeding societies.
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Affiliation(s)
- Martha J Nelson-Flower
- Percy FitzPatrick Institute of African Ornithology, DST/NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa.
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21
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Removal experiments indicate that subordinate stallions are not helpers. Behav Processes 2013; 94:1-4. [PMID: 23428706 DOI: 10.1016/j.beproc.2013.02.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 02/01/2013] [Accepted: 02/08/2013] [Indexed: 11/24/2022]
Abstract
Relationships between males defending the same harem are described as cooperative or competitive and explained by mutualism, reciprocal altruism, and reproductive concessions or limited control between unequal contestants. These alternate hypotheses can be tested by removing males from harems. Some feral horse (Equus caballus) harems are defended by more than one and up to five stallions. We temporarily removed the subordinate stallion from two of six multi-stallion bands (a harem and its stallions) for three weeks during the breeding season. We monitored harems for changes in composition, and measured and compared rates of (i) intra- and inter-band stallion aggression, (ii) stallion aggression towards mares, and (iii) stallion-mare proximity before subordinate stallion removal and after his return with rates during his absence. Harems were successfully defended during the subordinate's absence and stallion-mare aggression was substantially reduced. Dominant stallions did not require assistance in harem defence, and heightened harassment of mares is directly attributable to subordinate stallion's residence, not characteristics of the dominant stallion or mares. Cooperative hypotheses do not appear to explain multi-stallion bands but the experiments in this study should be replicated further. The limited control hypothesis (e.g., mate-parasitism) appears better supported but we outline its limitations too.
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22
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Hamilton IM. The effects of behavioral plasticity and leadership on the predictions of optimal skew models. Behav Ecol 2012. [DOI: 10.1093/beheco/ars182] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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23
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Snyder-Mackler N, Alberts SC, Bergman TJ. Concessions of an alpha male? Cooperative defence and shared reproduction in multi-male primate groups. Proc Biol Sci 2012; 279:3788-95. [PMID: 22764162 PMCID: PMC3415899 DOI: 10.1098/rspb.2012.0842] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 06/08/2012] [Indexed: 11/12/2022] Open
Abstract
By living in social groups with potential competitors, animals forgo monopolizing access to resources. Consequently, debate continues over how selection might favour sociality among competitors. For example, several models exist to account for the evolution of shared reproduction in groups. The 'concession model' hypothesizes that dominant reproducers benefit from the presence of subordinates, and hence tolerate some reproduction by subordinates. This mutual benefit to both dominants and subordinates may provide a foundation for the formation of social groups in which multiple members reproduce--a necessary step in the evolution of cooperation. To date, however, the concession model has received virtually no support in vertebrates. Instead, the vast majority of vertebrate data support 'limited control models', which posit that dominant reproducers are simply unable to prevent subordinates from reproducing. Here we present the most comprehensive evidence to date in support of the concession model in a vertebrate. We examined natural variation in the number of adult males in gelada (Theropithecus gelada) reproductive units to assess the extent of reproductive skew in multi-male units. Dominant ('leader') males in units that also had subordinate ('follower') males had a 30 per cent longer tenure than leaders in units that did not have followers, mainly because followers actively defended the group against potential immigrants. Follower males also obtained a small amount of reproduction in the unit, which may have functioned as a concession in return for defending the unit. These results suggest that dominants and subordinates may engage in mutually beneficial reproductive transactions, thus favouring male-male tolerance and cooperation.
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Affiliation(s)
- Noah Snyder-Mackler
- Department of Psychology, University of Pennsylvania, Philadelphia, PA, USA.
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24
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Nonacs P, Hager R. The past, present and future of reproductive skew theory and experiments. Biol Rev Camb Philos Soc 2011; 86:271-98. [PMID: 20545672 DOI: 10.1111/j.1469-185x.2010.00144.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A major evolutionary question is how reproductive sharing arises in cooperatively breeding species despite the inherent reproductive conflicts in social groups. Reproductive skew theory offers one potential solution: each group member gains or is allotted inclusive fitness equal to or exceeding their expectation from reproducing on their own. Unfortunately, a multitude of skew models with conflicting predictions has led to confusion in both testing and evaluating skew theory. The confusion arises partly because one set of models (the 'transactional' type) answer the ultimate evolutionary question of what ranges of reproductive skew can yield fitness-enhancing solutions for all group members. The second set of models ('compromise') give an evolutionarily proximate, game-theoretic evolutionarily stable state (ESS) solution that determines reproductive shares based on relative competitive abilities. However, several predictions arising from compromise models require a linear payoff to increased competition and do not hold with non-linear payoffs. Given that for most species it may be very difficult or impossible to determine the true relationship between effort devoted to competition and reproductive share gained, compromise models are much less predictive than previously appreciated. Almost all skew models make one quantitative prediction (e.g. realized skew must fall within ranges predicted by transactional models), and two qualitative predictions (e.g. variation in relatedness or competitive ability across groups affects skew). A thorough review of the data finds that these three predictions are relatively rarely supported. As a general rule, therefore, the evolution of cooperative breeding appears not to be dependent on the ability of group members to monitor relatedness or competitive ability in order to adjust their behaviour dynamically to gain reproductive share. Although reproductive skew theory fails to predict within-group dynamics consistently, it does better at predicting quantitative differences in skew across populations or species. This suggests that kin selection can play a significant role in the evolution of sociality. To advance our understanding of reproductive skew will require focusing on a broader array of factors, such as the frequency of mistaken identity, delayed fitness payoffs, and selection pressures arising from across-group competition. We furthermore suggest a novel approach to investigate the sharing of reproduction that focuses on the underlying genetics of skew. A quantitative genetics approach allows the partitioning of variance in reproductive share itself or that of traits closely associated with skew into genetic and non-genetic sources. Thus, we can determine the heritability of reproductive share and infer whether it actually is the focus of natural selection. We view the 'animal model' as the most promising empirical method where the genetics of reproductive share can be directly analyzed in wild populations. In the quest to assess whether skew theory can provide a framework for understanding the evolution of sociality, quantitative genetics will be a central tool in future research.
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Affiliation(s)
- Peter Nonacs
- Department of Ecology & Evolutionary Biology, University of California, Los Angeles, CA 90095, USA.
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25
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Shen SF, Reeve HK, Vehrencamp SL. Parental care, cost of reproduction and reproductive skew: a general costly young model. J Theor Biol 2011; 284:24-31. [PMID: 21703276 DOI: 10.1016/j.jtbi.2011.05.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Revised: 04/15/2011] [Accepted: 05/23/2011] [Indexed: 10/18/2022]
Abstract
Understanding the mechanisms by which animals resolve conflicts of interest is the key to understanding the basis of cooperation in social species. Conflict over reproductive portioning is the critical type of conflict among cooperative breeders. The costly young model represents an important, but underappreciated, idea about how an individual's intrinsic condition and cost of reproduction should affect the resolution of conflict over the distribution of reproduction within a cooperatively breeding group. However, dominant control in various forms and fixed parental care (offspring fitness dependent solely on total brood size) are assumed in previous versions of costly young models. Here, we develop a general costly young model by relaxing the restrictive assumptions of existing models. Our results show that (1) when the complete-control assumption is relaxed, the costly young model behaves very differently from the original model, and (2) when the fixed parental care assumption is relaxed, the costly young-costly care model displays similar predictions to the tug-of-war model, although the underlying mechanisms causing these similar patterns are different. These results, we believe, help simplify the seemingly divergent predictions of different reproductive skew models and highlight the importance of studying the group members' intrinsic conditions, costs of producing young, and costs of parental care for understanding breeding conflict resolution in cooperatively breeding animals.
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Affiliation(s)
- Sheng-Feng Shen
- Biodiversity Research Center, Academia Sinica, Taipei 106, Taiwan.
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26
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Lucas ER, Martins RP, Field J. Reproductive skew is highly variable and correlated with genetic relatedness in a social apoid wasp. Behav Ecol 2011. [DOI: 10.1093/beheco/arq214] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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27
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Nonacs P. Bordered tug-of-war models are neither general nor predictive of reproductive skew. J Theor Biol 2010; 266:739-41. [DOI: 10.1016/j.jtbi.2010.07.029] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2010] [Revised: 05/21/2010] [Accepted: 07/23/2010] [Indexed: 10/19/2022]
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28
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Jaatinen K, Ost M, Lehikoinen A. Adult predation risk drives shifts in parental care strategies: a long-term study. J Anim Ecol 2010; 80:49-56. [PMID: 20880024 DOI: 10.1111/j.1365-2656.2010.01757.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
1. Grouping provides antipredatory benefits, and therefore aggregation tendencies increase under heightened predation risk. In socially breeding groups, however, conflicts over reproductive shares or safety tend to disintegrate groups. Group formation thereby involves a balance between the antipredatory benefits of aggregation and the destabilizing effect of reproductive conflict. 2. We study the grouping behaviour of a facultatively social precocial sea duck with uniparental female care, the eider (Somateria mollissima Linnaeus). Females tend their young solitarily or in groups of 2-5 females. Here, we focus on the effect predation on adults has on group-formation decisions of brood-caring females. 3. By modifying an existing bidding game over care, we model the effects of predation risk on the width of the window of selfishness, which delimits the reproductive sharing allowing cooperation within brood-rearing coalitions, and generate predictions about the relative frequencies of solitary versus cooperative parental care modes. Furthermore, we model the dilution effect as a function of female group size and predation risk. 4. The window of selfishness widens with increasing predation risk, and the dilution of predation risk increases with both female group size and increasing predation risk, yielding the following predictions: (i) cooperative brood care becomes more prevalent and, conversely, solitary brood care less prevalent under heightened predation risk and (ii) group sizes increase concomitantly. 5. We tested these predictions using 13 years of data on female grouping decisions and annual predation rates, while controlling for the potentially confounding effect of female body condition. 6. Our data supported both predictions, where heightened predation risk of nesting females, but not changes in their condition, increased the relative frequency of cooperative brood care. Increased female nesting mortality also resulted in larger groups of cooperative females. 7. The predation risk of incubating females has long-term implications for later parental care decisions. We discuss the potential consequences of predation-induced shifts in group size on per capita fitness and population-wide productivity.
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Affiliation(s)
- Kim Jaatinen
- ARONIA Coastal Zone Research Team, Åbo Akademi University and Novia University of Applied Sciences, Raseborgsvägen 9, FI-10600 Ekenäs, Finland.
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29
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Cant MA, Hodge SJ, Bell MBV, Gilchrist JS, Nichols HJ. Reproductive control via eviction (but not the threat of eviction) in banded mongooses. Proc Biol Sci 2010; 277:2219-26. [PMID: 20236979 PMCID: PMC2880142 DOI: 10.1098/rspb.2009.2097] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Considerable research has focused on understanding variation in reproductive skew in cooperative animal societies, but the pace of theoretical development has far outstripped empirical testing of the models. One major class of model suggests that dominant individuals can use the threat of eviction to deter subordinate reproduction (the ‘restraint’ model), but this idea remains untested. Here, we use long-term behavioural and genetic data to test the assumptions of the restraint model in banded mongooses (Mungos mungo), a species in which subordinates breed regularly and evictions are common. We found that dominant females suffer reproductive costs when subordinates breed, and respond to these costs by evicting breeding subordinates from the group en masse, in agreement with the assumptions of the model. We found no evidence, however, that subordinate females exercise reproductive restraint to avoid being evicted in the first place. This means that the pattern of reproduction is not the result of a reproductive ‘transaction’ to avert the threat of eviction. We present a simple game theoretical analysis that suggests that eviction threats may often be ineffective to induce pre-emptive restraint among multiple subordinates and predicts that threats of eviction (or departure) will be much more effective in dyadic relationships and linear hierarchies. Transactional models may be more applicable to these systems. Greater focus on testing the assumptions rather than predictions of skew models can lead to a better understanding of how animals control each other's reproduction, and the extent to which behaviour is shaped by overt acts versus hidden threats.
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Affiliation(s)
- Michael A Cant
- Centre for Ecology and Conservation, University of Exeter in Cornwall, Penryn, Cornwall TR10 9EZ, UK.
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30
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Port M, Kappeler PM. The utility of reproductive skew models in the study of male primates, a critical evaluation. Evol Anthropol 2010. [DOI: 10.1002/evan.20243] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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31
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Shen SF, Kern Reeve H. Reproductive skew theory unified: The general bordered tug-of-war model. J Theor Biol 2010; 263:1-12. [DOI: 10.1016/j.jtbi.2009.11.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Revised: 11/12/2009] [Accepted: 11/12/2009] [Indexed: 11/16/2022]
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32
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Schradin C, König B, Pillay N. Reproductive competition favours solitary living while ecological constraints impose group-living in African striped mice. J Anim Ecol 2010; 79:515-21. [PMID: 20059610 DOI: 10.1111/j.1365-2656.2009.01651.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
1. Social groups typically form due to delayed dispersal of adult offspring when no opportunities for independent breeding exist, or the costs of dispersal are higher than the costs of remaining philopatric. Ecological constraints are thought to be a main reason for group-living in animals. 2. Reproductive competition within groups can induce high costs of philopatry, and is thought to be a main reason for solitary living. 3. Experimental manipulation of reproductive competition is difficult. One solution is to compare sociality between periods with and without reproductive competition. 4. Here, we show empirically in a 8-year field study that striped mice (Rhabdomys pumilio) of both sexes were group-living during the breeding season when population density (PD) was high but solitary living when PD was low, supporting the ecological constraints model. 5. After the breeding season, in the absence of reproductive competition, the positive correlation between PD and percentage of group-living striped mice was absent. Almost all striped mice were group-living even under very low population densities. This supports the reproductive competition model. 6. Ambient temperature, food availability and predation pressure, did not influence sociality. 7. In captivity, the costs of reproductive competition in communal groups include female infanticide and aggression between females. 8. We conclude that group-living is favoured by constraints imposed through habitat saturation and by its benefits (improved thermoregulation by huddling, group-territoriality and predator avoidance), and that reproductive competition is a major force favouring solitary living in striped mice.
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Affiliation(s)
- Carsten Schradin
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland.
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33
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Cant MA, Johnstone RA. How threats influence the evolutionary resolution of within-group conflict. Am Nat 2009; 173:759-71. [PMID: 19374506 DOI: 10.1086/598489] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Most examples of cooperation in nature share a common feature: individuals can interact to produce a productivity benefit or fitness surplus, but there is conflict over how these gains are shared. A central question is how threats to exercise outside options influence the resolution of conflict within such cooperative associations. Here we show how a simple principle from economic bargaining theory, the outside option principle, can help to solve this problem in biological systems. According to this principle, outside options will affect the resolution of conflict only when the payoff of taking up these options exceeds the payoffs individuals can obtain from bargaining or negotiating within the group; otherwise, threats to exercise outside options are not credible and are therefore irrelevant. We show that previous attempts to incorporate outside options in synthetic models of reproductive conflict fail to distinguish between credible and incredible threats, and then we use the outside option principle to develop credible synthetic models in two contexts: reproductive skew and biparental care. A striking prediction of our analysis is that outside options are least relevant to the resolution of conflict in cooperative groups of kin and are most relevant in transient associations or interactions among nonrelatives. Our analysis shows a way to link the resolution of within-group conflict to the environmental setting in which it occurs, and it illuminates the role of threats in the evolution of social behavior.
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Affiliation(s)
- Michael A Cant
- Centre for Ecology and Conservation, University of Exeter, Cornwall Campus, Tremough, Penryn, Cornwall TR10 9EZ, United Kingdom.
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34
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Rubenstein D, Shen S. Reproductive Conflict and the Costs of Social Status in Cooperatively Breeding Vertebrates. Am Nat 2009; 173:650-61. [DOI: 10.1086/597606] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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35
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Buston PM, Zink AG. Reproductive skew and the evolution of conflict resolution: a synthesis of transactional and tug-of-war models. Behav Ecol 2009. [DOI: 10.1093/beheco/arp050] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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36
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Saltzman W, Digby LJ, Abbott DH. Reproductive skew in female common marmosets: what can proximate mechanisms tell us about ultimate causes? Proc Biol Sci 2009; 276:389-99. [PMID: 18945663 PMCID: PMC2592602 DOI: 10.1098/rspb.2008.1374] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2008] [Accepted: 09/26/2008] [Indexed: 11/12/2022] Open
Abstract
Common marmosets are cooperatively breeding monkeys that exhibit high reproductive skew: most subordinate females fail to reproduce, while others attempt to breed but produce very few surviving infants. An extensive dataset on the mechanisms limiting reproduction in laboratory-housed and free living subordinate females provides unique insights into the causes of reproductive skew. Non-breeding adult females undergo suppression of ovulation and inhibition of sexual behaviour; however, they receive little or no aggression or mating interference by dominants and do not exhibit behavioural or physiological signs of stress. Breeding subordinate females receive comparable amounts of aggression to non-breeding females but are able to conceive, gestate and lactate normally. In groups containing two breeding females,however, both dominant and subordinate breeders kill one another's infants. These findings suggest that preconception reproductive suppression is not imposed on subordinate females by dominants, at a proximate level, but is instead self-imposed by most subordinates, consistent with restraint models of reproductive skew. In contrast to restraint models, however, this self-suppression probably evolved not in response to the threat of eviction by dominant females but in response to the threat of infanticide. Thus,reproductive skew in this species appears to be generated predominantly by subordinate self-restraint, in a proximate sense, but ultimately by dominant control over subordinates' reproductive attempts.
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Affiliation(s)
- Wendy Saltzman
- Department of Biology, University of California, Riverside, CA 92521, USA.
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37
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Townsend AK, Clark AB, McGowan KJ, Lovette IJ. Reproductive partitioning and the assumptions of reproductive skew models in the cooperatively breeding American crow. Anim Behav 2009; 77:503-512. [PMID: 20126287 DOI: 10.1016/j.anbehav.2008.10.030] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Understanding the benefits of cooperative breeding for group members of different social and demographic classes requires knowledge of their reproductive partitioning and genetic relatedness. From 2004-2007, we examined parentage as a function of relatedness and social interactions among members of 21 American crow (Corvus brachyrhynchos) family groups. Paired female breeders monopolized maternity of all offspring in their broods, whereas paired male breeders sired 82.7% of offspring, within-group auxiliary males sired 6.9% of offspring, and extragroup males sired 10.4% of offspring. Although adult females had fewer opportunities for direct reproduction as auxiliaries than males, they appeared to have earlier opportunities for independent breeding. These different opportunities for direct reproduction probably contributed to the male biased adult auxiliary sex ratio. Patterns of reproductive partitioning and conflict among males were most consistent with a synthetic reproductive skew model, in which auxiliaries struggled with breeders for a limited reproductive share, beyond which breeders could evict them. Counter to a frequent assumption of reproductive skew models, female breeders appeared to influence paternity, although their interests might have agreed with the interests of their paired males. Unusual among cooperative breeders, close inbreeding and incest occurred in this population. Incest avoidance between potential breeders did not significantly affect reproductive skew.
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Affiliation(s)
- Andrea K Townsend
- Fuller Evolutionary Biology Program, Cornell University Laboratory of Ornithology, Ithaca, NY
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38
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Clutton-Brock T, Hodge S, Flower T. Group size and the suppression of subordinate reproduction in Kalahari meerkats. Anim Behav 2008. [DOI: 10.1016/j.anbehav.2008.03.015] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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39
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Competition and waste in the communally breeding smooth-billed ani: effects of group size on egg-laying behaviour. Anim Behav 2008. [DOI: 10.1016/j.anbehav.2007.12.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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40
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Mutual tolerance or reproductive competition? Patterns of reproductive skew among male redfronted lemurs (Eulemur fulvus rufus). Behav Ecol Sociobiol 2008. [DOI: 10.1007/s00265-008-0577-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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41
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Tibbetts EA, Reeve HK. Two experimental tests of the relationship between group stability and aggressive conflict in Polistes wasps. Naturwissenschaften 2008; 95:383-9. [PMID: 18183360 DOI: 10.1007/s00114-007-0336-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2006] [Revised: 10/12/2007] [Accepted: 12/10/2007] [Indexed: 10/22/2022]
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42
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The lemur syndrome unresolved: extreme male reproductive skew in sifakas (Propithecus verreauxi), a sexually monomorphic primate with female dominance. Behav Ecol Sociobiol 2007. [DOI: 10.1007/s00265-007-0528-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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43
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Buston P, Reeve H, Cant M, Vehrencamp S, Emlen S. Reproductive skew and the evolution of group dissolution tactics: a synthesis of concession and restraint models. Anim Behav 2007. [DOI: 10.1016/j.anbehav.2007.03.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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44
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Sachs JL, Rubenstein DR. The evolution of cooperative breeding; is there cheating? Behav Processes 2007; 76:131-7. [PMID: 17764858 DOI: 10.1016/j.beproc.2006.12.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Accepted: 12/21/2006] [Indexed: 11/17/2022]
Affiliation(s)
- Joel L Sachs
- Department of Integrative Biology, University of California, Berkeley, USA.
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45
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Reeve HK, Hölldobler B. The emergence of a superorganism through intergroup competition. Proc Natl Acad Sci U S A 2007; 104:9736-40. [PMID: 17517608 PMCID: PMC1887545 DOI: 10.1073/pnas.0703466104] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2007] [Indexed: 11/18/2022] Open
Abstract
Surveys of insect societies have revealed four key, recurring organizational trends: (i) The most elaborated cooperation occurs in groups of relatives. (ii) Cooperation is typically more elaborate in species with large colony sizes than in species with small colony sizes, the latter exhibiting greater internal reproductive conflict and lesser morphological and behavioral specialization. (iii) Within a species, per capita brood output typically declines as colony size increases. (iv). The ecological factors of resource patchiness and intergroup competition are associated with the most elaborated cooperation. Predictions of all four patterns emerge elegantly from a game-theoretic model in which within-group tug-of-wars are nested within a between-group tug-of-war. In this individual selection model, individuals are faced with the problem of how to partition their energy between investment in intercolony competition versus investment in intracolony competition, i.e., internal tugs-of-war over shares of the resources gained through intergroup competition. An individual's evolutionarily stable investment in between-group competition (i.e., within-group cooperation) versus within-group competition is shown to increase as within-group relatedness increases, to decrease as group size increases (for a fixed number of competing groups), to increase as the number of competing groups in a patch increases, and to decrease as between-group relatedness increases. Moreover, if increasing patch richness increases both the number of individuals within a group and the number of competing groups, greater overall cooperation within larger groups will be observed. The model presents a simple way of determining quantitatively how intergroup conflict will propel a society forward along a "superorganism continuum."
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Affiliation(s)
- H. Kern Reeve
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853
| | - Bert Hölldobler
- School of Life Sciences, Center for Social Dynamics and Complexity, Arizona State University, Tempe, AZ 85287-4501; and
- Biozentrum, University of Würzburg, 97070 Würzburg, Germany
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46
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Rubenstein DR. Stress hormones and sociality: integrating social and environmental stressors. Proc Biol Sci 2007; 274:967-75. [PMID: 17251100 PMCID: PMC2141667 DOI: 10.1098/rspb.2006.0051] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2006] [Revised: 12/16/2006] [Accepted: 12/18/2006] [Indexed: 11/12/2022] Open
Abstract
In cooperatively breeding species, reproductive decisions and breeding roles may be influenced by environmental (food resources) or social factors (reproductive suppression of subordinates by dominants). Studies of glucocorticoid stress hormones in cooperatively breeding species suggest that breeding roles and hormone levels are related to the relative costs of dominance and subordination, which are driven primarily by social interactions. Few studies, however, have considered how environmental factors affect glucocorticoid levels and breeding roles in cooperative breeders, even though environmental stressors modulate seasonal glucocorticoid release and often influence breeding roles. I examined baseline and stress-induced levels of the glucocorticoid corticosterone (CORT) across 4 years in the plural breeding superb starling, Lamprotornis superbus, to determine whether (i) environmental factors (namely rainfall) directly influence breeding roles or (ii) environmental factors influence social interactions, which in turn drive breeding roles. Chronic baseline and maximal stress-induced CORT changed significantly across years as a function of pre-breeding rainfall, but dominant and subordinate individuals responded differently. Pre-breeding rainfall was also correlated directly with breeding roles. The results are most consistent with the hypothesis that environmental conditions influenced the relative costs of dominance and subordination, which in turn affected the degree and intensity of social interactions and ultimately reproductive decisions and breeding roles.
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Affiliation(s)
- Dustin R Rubenstein
- Department of Neurobiology and Behavior, Cornell University, Seeley G. Mudd Hall, Ithaca, NY 14853-2702, USA.
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Abstract
Cooperative breeding often results in unequal reproduction between dominant and subordinate group members. Transactional skew models attempt to predict how unequal reproduction can be before the groups themselves become unstable. A number of variants of transactional models have been developed, with a key difference being whether reproduction is controlled by one party or contested by all. It is shown here that ESS solutions for all situations of contested control over reproduction are given by the original tug-of-war model (TOW). Several interesting results follow. First, TOW can escalate enough to destabilize some types of groups. Particularly vulnerable are those that have low relatedness and gain little from cooperative breeding relative to solitary reproduction. Second, TOW can drastically reduce group productivity and especially the inclusive fitness of dominant individuals. Third, these results contrast strongly with those from variants of TOW models that include concessions to maintain group stability. Such models are shown to be special cases of the general and simpler TOW framework, and to have assumptions that may be biologically suspect. Finally, the overall analysis suggests that there is no mechanism within existing TOW framework that will prevent a costly struggle for reproductive control. Because social species rarely exhibit the high levels of aggression predicted by TOW models, alternative evolutionary mechanisms are considered that can limit conflict and produce more mutually beneficial outcomes. The further development of alternative models to predict patterns of reproductive skew are highly recommended.
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Affiliation(s)
- Peter Nonacs
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California 90095, USA.
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