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Flatrès A, Wild G. Evolution of delayed dispersal with group size effect and population dynamics. Theor Popul Biol 2024; 157:1-13. [PMID: 38417560 DOI: 10.1016/j.tpb.2024.02.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 01/19/2024] [Accepted: 02/19/2024] [Indexed: 03/01/2024]
Abstract
Individuals delay natal dispersal for many reasons. There may be no place to disperse to; immediate dispersal or reproduction may be too costly; immediate dispersal may mean that the individual and their relatives miss the benefits of group living. Understanding the factors that lead to the evolution of delayed dispersal is important because delayed dispersal sets the stage for complex social groups and social behavior. Here, we study the evolution of delayed dispersal when the quality of the local environment is improved by greater numbers of individuals (e.g., safety in numbers). We assume that individuals who delay natal dispersal also expect to delay personal reproduction. In addition, we assume that improved environmental quality benefits manifest as changes to fecundity and survival. We are interested in how do the changes in these life-history features affect delayed dispersal. We use a model that ties evolution to population dynamics. We also aim to understand the relationship between levels of delayed dispersal and the probability of establishing as an independent breeder (a population-level feature) in response to changes in life-history details. Our model emphasizes kin selection and considers a sexual organism, which allows us to study parent-offspring conflict over delayed dispersal. At evolutionary equilibrium, fecundity and survival benefits of group size or quality promote higher levels of delayed dispersal over a larger set of life histories with one exception. The exception is for benefits of increased group size or quality reaped by the individuals who delay dispersal. There, the increased benefit does not change the life histories supporting delay dispersal. Next, in contrast to previous predictions, we find that a low probability of establishing in a new location is not always associated with a higher incidence of delayed dispersal. Finally, we find that increased personal benefits of delayed dispersal exacerbate the conflict between parents and their offspring. We discuss our findings in relation to previous theoretical and empirical work, especially work related to cooperative breeding.
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Affiliation(s)
- Alan Flatrès
- Department of Mathematics, Western University, 1151 Richmond Street, London, Ontario, N6A 5B7, Canada.
| | - Geoff Wild
- Department of Mathematics, Western University, 1151 Richmond Street, London, Ontario, N6A 5B7, Canada
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Bourne AR, Ridley AR, Cunningham SJ. Helpers don't help when it's hot in a cooperatively breeding bird, the Southern Pied Babbler. Behav Ecol 2023; 34:562-570. [PMID: 37434640 PMCID: PMC10332451 DOI: 10.1093/beheco/arad023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 02/25/2023] [Accepted: 04/04/2023] [Indexed: 07/13/2023] Open
Abstract
Cooperative breeding, where more than two individuals invest in rearing a single brood, occurs in many bird species globally and often contributes to improved breeding outcomes. However, high temperatures are associated with poor breeding outcomes in many species, including cooperative species. We used data collected over three austral summer breeding seasons to investigate the contribution that helpers make to daytime incubation in a cooperatively breeding species, the Southern Pied Babbler Turdoides bicolor, and the ways in which their contribution is influenced by temperature. Helpers spent a significantly higher percentage of their time foraging (41.8 ± 13.7%) and a significantly lower percentage of their time incubating (18.5 ± 18.8%) than members of the breeding pair (31.3 ± 11% foraging and 37.4 ± 15.7% incubating). In groups with only one helper, the helper's contribution to incubation was similar to that of breeders. However, helpers in larger groups contributed less to incubation, individually, with some individuals investing no time in incubation on a given observation day. Helpers significantly decrease their investment in incubation on hot days (>35.5°C), while breeders tend to maintain incubation effort as temperatures increase. Our results demonstrate that pied babblers share the workload of incubation unequally between breeders and helpers, and this inequity is more pronounced during hot weather. These results may help to explain why recent studies have found that larger group size does not buffer against the impacts of high temperatures in this and other cooperatively breeding species.
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Affiliation(s)
| | - Amanda R Ridley
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
- Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia, Crawley 6009, Australia
| | - Susan J Cunningham
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
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Shah SS, Rubenstein DR. Group augmentation underlies the evolution of complex sociality in the face of environmental instability. Proc Natl Acad Sci U S A 2023; 120:e2212211120. [PMID: 37094171 PMCID: PMC10160950 DOI: 10.1073/pnas.2212211120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 03/16/2023] [Indexed: 04/26/2023] Open
Abstract
Although kin selection is assumed to underlie the evolution of sociality, many vertebrates-including nearly half of all cooperatively breeding birds-form groups that also include unrelated individuals. Theory predicts that despite reducing kin structure, immigration of unrelated individuals into groups can provide direct, group augmentation benefits, particularly when offspring recruitment is insufficient for group persistence. Using population dynamic modeling and analysis of long-term data, we provide clear empirical evidence of group augmentation benefits favoring the evolution and maintenance of complex societies with low kin structure and multiple reproductives. We show that in the superb starling (Lamprotornis superbus)-a plural cooperative breeder that forms large groups with multiple breeding pairs, and related and unrelated nonbreeders of both sexes-offspring recruitment alone cannot prevent group extinction, especially in smaller groups. Further, smaller groups, which stand to benefit more from immigration, exhibit lower reproductive skew for immigrants, suggesting that reproductive opportunities as joining incentives lead to plural breeding. Yet, despite a greater likelihood of becoming a breeder in smaller groups, immigrants are more likely to join larger groups where they experience increased survivorship and greater reproductive success as breeders. Moreover, immigrants form additional breeding pairs, increasing future offspring recruitment into the group and guarding against complete reproductive failure in the face of environmental instability and high nest predation. Thus, plural breeding likely evolves because the benefits of group augmentation by immigrants generate a positive feedback loop that maintains societies with low and mixed kinship, large group sizes, and multiple reproductives.
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Affiliation(s)
- Shailee S. Shah
- Department of Ecology, Evolution, and Environmental Biology, Columbia University, New York, NY10027
| | - Dustin R. Rubenstein
- Department of Ecology, Evolution, and Environmental Biology, Columbia University, New York, NY10027
- Center for Integrative Animal Behavior, Columbia University, New York, NY10027
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Braga Goncalves I, Morris-Drake A, Kennedy P, Radford AN. Fitness consequences of outgroup conflict. eLife 2022; 11:e74550. [PMID: 35833830 PMCID: PMC9282852 DOI: 10.7554/elife.74550] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 06/27/2022] [Indexed: 12/13/2022] Open
Abstract
In social species across the animal kingdom, conspecific outsiders threaten the valuable resources of groups and their members. This outgroup conflict is recognised as a powerful selection pressure, but we argue that studies explicitly quantifying the fitness consequences need to be broader in scope: more attention should be paid to delayed, cumulative, and third-party fitness consequences, not just those arising immediately to group members involved in physical contests. In the first part of this review, we begin by documenting how single contests can have survival and reproductive consequences either immediately or with a delay. Then, we step beyond contests to describe fitness consequences that can also result from interactions with cues of rival presence and the general landscape of outgroup threat, and beyond single interactions to describe cumulative effects of territorial pressure and elevated outgroup-induced stress. Using examples from a range of taxa, we discuss which individuals are affected negatively and positively, considering both interaction participants and third-party group members of the same or the next generation. In the second part of the review, we provide suggestions about how to move forward. We highlight the importance of considering how different types of outgroup conflict can generate different selection pressures and of investigating variation in fitness consequences within and between species. We finish by discussing the value of theoretical modelling and long-term studies of natural populations, experimental manipulations, and meta-analyses to develop further our understanding of this crucial aspect of sociality.
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Affiliation(s)
| | - Amy Morris-Drake
- School of Biological Sciences, University of BristolBristolUnited Kingdom
| | - Patrick Kennedy
- School of Biological Sciences, University of BristolBristolUnited Kingdom
| | - Andrew N Radford
- School of Biological Sciences, University of BristolBristolUnited Kingdom
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Massaro AP, Gilby IC, Desai N, Weiss A, Feldblum JT, Pusey AE, Wilson ML. Correlates of individual participation in boundary patrols by male chimpanzees. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210151. [PMID: 35369753 DOI: 10.1098/rstb.2021.0151] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Group territory defence poses a collective action problem: individuals can free-ride, benefiting without paying the costs. Individual heterogeneity has been proposed to solve such problems, as individuals high in reproductive success, rank, fighting ability or motivation may benefit from defending territories even if others free-ride. To test this hypothesis, we analysed 30 years of data from chimpanzees (Pan troglodytes) in the Kasekela community, Gombe National Park, Tanzania (1978-2007). We examined the extent to which individual participation in patrols varied according to correlates of reproductive success (mating rate, rank, age), fighting ability (hunting), motivation (scores from personality ratings), costs of defecting (the number of adult males in the community) and gregariousness (sighting frequency). By contrast to expectations from collective action theory, males participated in patrols at consistently high rates (mean ± s.d. = 74.5 ± 11.1% of patrols, n = 23 males). The best predictors of patrol participation were sighting frequency, age and hunting participation. Current and former alpha males did not participate at a higher rate than males that never achieved alpha status. These findings suggest that the temptation to free-ride is low, and that a mutualistic mechanism such as group augmentation may better explain individual participation in group territorial behaviour. This article is part of the theme issue 'Intergroup conflict across taxa'.
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Affiliation(s)
- Anthony P Massaro
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN 55414, USA
| | - Ian C Gilby
- School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85281, USA.,Institute of Human Origins, Arizona State University, Tempe, AZ 85281, USA
| | - Nisarg Desai
- Department of Anthropology, University of Minnesota, Minneapolis, MN 55414, USA
| | - Alexander Weiss
- National Evolutionary Synthesis Center, Durham, NC 27705, USA.,Department of Psychology, School of Philosophy, Psychology and Language Sciences, University of Edinburgh, 7 George Square, Edinburgh EH8 9JZ, UK
| | - Joseph T Feldblum
- Department of Anthropology, University of Michigan, Ann Arbor, MI 48109, USA.,Society of Fellows, University of Michigan, Ann Arbor, MI 48109, USA
| | - Anne E Pusey
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
| | - Michael L Wilson
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN 55414, USA.,Department of Anthropology, University of Minnesota, Minneapolis, MN 55414, USA.,Institute on the Environment, University of Minnesota, St. Paul, MN 55414, USA
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Ridley AR, Nelson-Flower MJ, Wiley EM, Humphries DJ, Kokko H. Kidnapping intergroup young: an alternative strategy to maintain group size in the group-living pied babbler ( Turdoides bicolor). Philos Trans R Soc Lond B Biol Sci 2022; 377:20210153. [PMID: 35369755 PMCID: PMC8977656 DOI: 10.1098/rstb.2021.0153] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Both inter- and intragroup interactions can be important influences on behaviour, yet to date most research focuses on intragroup interactions. Here, we describe a hitherto relatively unknown behaviour that results from intergroup interaction in the cooperative breeding pied babbler: kidnapping. Kidnapping can result in the permanent removal of young from their natal group. Since raising young requires energetic investment and abductees are usually unrelated to their kidnappers, there appears no apparent evolutionary advantage to kidnapping. However, kidnapping may be beneficial in species where group size is a critically limiting factor (e.g. for reproductive success or territory defence). We found kidnapping was a highly predictable event in pied babblers: primarily groups that fail to raise their own young kidnap the young of others, and we show this to be the theoretical expectation in a model that predicts kidnapping to be facultative, only occurring in those cases where an additional group member has sufficient positive impact on group survival to compensate for the increase in reproductive competition. In babblers, groups that failed to raise young were also more likely to accept extragroup adults (hereafter rovers). Groups that fail to breed may either (i) kidnap intergroup young or (ii) accept rovers as an alternative strategy to maintain or increase group size. This article is part of the theme issue 'Intergroup conflict across taxa'.
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Affiliation(s)
- Amanda R Ridley
- Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia, Perth, Australia.,Percy FitzPatrick Institute of African Ornithology, University of Cape Town, Cape Town, Western Cape, South Africa
| | - Martha J Nelson-Flower
- Percy FitzPatrick Institute of African Ornithology, University of Cape Town, Cape Town, Western Cape, South Africa.,Department of Biology, Langara College, Vancouver, BC, Canada
| | - Elizabeth M Wiley
- Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia, Perth, Australia
| | - David J Humphries
- Percy FitzPatrick Institute of African Ornithology, University of Cape Town, Cape Town, Western Cape, South Africa
| | - Hanna Kokko
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
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De Dreu CKW, Triki Z. Intergroup conflict: origins, dynamics and consequences across taxa. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210134. [PMID: 35369751 PMCID: PMC8977662 DOI: 10.1098/rstb.2021.0134] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Although uniquely destructive and wasteful, intergroup conflict and warfare are not confined to humans. They are seen across a range of group-living species, from social insects, fishes and birds to mammals, including nonhuman primates. With its unique collection of theory, research and review contributions from biology, anthropology and economics, this theme issue provides novel insights into intergroup conflict across taxa. Here, we introduce and organize this theme issue on the origins and consequences of intergroup conflict. We provide a coherent framework by modelling intergroup conflicts as multi-level games of strategy in which individuals within groups cooperate to compete with (individuals in) other groups for scarce resources, such as territory, food, mating opportunities, power and influence. Within this framework, we identify cross-species mechanisms and consequences of (participating in) intergroup conflict. We conclude by highlighting crosscutting innovations in the study of intergroup conflict set forth by individual contributions. These include, among others, insights on how within-group heterogeneities and leadership relate to group conflict, how intergroup conflict shapes social organization and how climate change and environmental degradation transition intergroup relations from peaceful coexistence to violent conflict. This article is part of the theme issue ‘Intergroup conflict across taxa’.
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Affiliation(s)
- Carsten K W De Dreu
- Institute of Psychology, Leiden University, Leiden, The Netherlands.,Center for Research in Experimental Economics and Political Decision Making, University of Amsterdam, Amsterdam, The Netherlands
| | - Zegni Triki
- Department of Zoology, Stockholm University, Stockholm, Sweden
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