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Kerr NZ, Morris WF, Walters JR. Inclusive Fitness May Explain Some but Not All Benefits Derived from Helping Behavior in a Cooperatively Breeding Bird. Am Nat 2024; 203:393-410. [PMID: 38358814 DOI: 10.1086/728670] [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] [Indexed: 02/17/2024]
Abstract
AbstractIn cooperative breeding systems, inclusive fitness theory predicts that nonbreeding helpers more closely related to the breeders should be more willing to provide costly alloparental care and thus have more impact on breeder fitness. In the red-cockaded woodpecker (Dryobates borealis), most helpers are the breeders' earlier offspring, but helpers do vary within groups in both relatedness to the breeders (some even being unrelated) and sex, and it can be difficult to parse their separate impacts on breeder fitness. Moreover, most support for inclusive fitness theory has been positive associations between relatedness and behavior rather than actual fitness consequences. We used functional linear models to evaluate the per capita effects of helpers of different relatedness on eight breeder fitness components measured for up to 41 years at three sites. In support of inclusive fitness theory, helpers more related to the breeding pair made greater contributions to six fitness components. However, male helpers made equal contributions to increasing prefledging survival regardless of relatedness. These findings suggest that both inclusive fitness benefits and other direct benefits may underlie helping behaviors in the red-cockaded woodpecker. Our results also demonstrate the application of an underused statistical approach to disentangle a complex ecological phenomenon.
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2
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Leeks A, Bono LM, Ampolini EA, Souza LS, Höfler T, Mattson CL, Dye AE, Díaz-Muñoz SL. Open questions in the social lives of viruses. J Evol Biol 2023; 36:1551-1567. [PMID: 37975507 DOI: 10.1111/jeb.14203] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Revised: 06/12/2023] [Accepted: 06/21/2023] [Indexed: 11/19/2023]
Abstract
Social interactions among viruses occur whenever multiple viral genomes infect the same cells, hosts, or populations of hosts. Viral social interactions range from cooperation to conflict, occur throughout the viral world, and affect every stage of the viral lifecycle. The ubiquity of these social interactions means that they can determine the population dynamics, evolutionary trajectory, and clinical progression of viral infections. At the same time, social interactions in viruses raise new questions for evolutionary theory, providing opportunities to test and extend existing frameworks within social evolution. Many opportunities exist at this interface: Insights into the evolution of viral social interactions have immediate implications for our understanding of the fundamental biology and clinical manifestation of viral diseases. However, these opportunities are currently limited because evolutionary biologists only rarely study social evolution in viruses. Here, we bridge this gap by (1) summarizing the ways in which viruses can interact socially, including consequences for social evolution and evolvability; (2) outlining some open questions raised by viruses that could challenge concepts within social evolution theory; and (3) providing some illustrative examples, data sources, and conceptual questions, for studying the natural history of social viruses.
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Affiliation(s)
- Asher Leeks
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, USA
- Quantitative Biology Institute, Yale University, New Haven, Connecticut, USA
| | - Lisa M Bono
- Department of Biological Sciences, Texas Tech University, Lubbock, Texas, USA
| | - Elizabeth A Ampolini
- Department of Biochemistry & Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Lucas S Souza
- Department of Ecology & Evolutionary Biology, University of Tennessee, Knoxville, Tennessee, USA
| | - Thomas Höfler
- Institute of Virology, Freie Universität Berlin, Berlin, Germany
| | - Courtney L Mattson
- Department of Microbiology and Molecular Genetics, University of California Davis, Davis, California, USA
| | - Anna E Dye
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, USA
| | - Samuel L Díaz-Muñoz
- Department of Microbiology and Molecular Genetics, University of California Davis, Davis, California, USA
- Genome Center, University of California Davis, Davis, California, USA
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3
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Thorley J, Bensch HM, Finn K, Clutton-Brock T, Zöttl M. Damaraland mole-rats do not rely on helpers for reproduction or survival. Evol Lett 2023; 7:203-215. [PMID: 37475748 PMCID: PMC10355180 DOI: 10.1093/evlett/qrad023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 03/23/2023] [Accepted: 05/05/2023] [Indexed: 07/22/2023] Open
Abstract
In eusocial invertebrates and obligate cooperative breeders, successful reproduction is dependent on assistance from non-breeding group members. Although naked (Heterocephalus glaber) and Damaraland mole-rats (Fukomys damarensis) are often described as eusocial and their groups are suggested to resemble those of eusocial insects more closely than groups of any other vertebrate, the extent to which breeding individuals benefit from the assistance of non-breeding group members is unclear. Here we show that, in wild Damaraland mole-rats, prospective female breeders usually disperse and settle alone in new burrow systems where they show high survival rates and remain in good body condition-often for several years-before being joined by males. In contrast to many obligate cooperative vertebrates, pairs reproduced successfully without non-breeding helpers, and the breeding success of experimentally formed pairs was similar to that of larger, established groups. Though larger breeding groups recruited slightly more pups than smaller groups, adult survival was independent of group size and group size had mixed effects on the growth of non-breeders. Our results suggest that Damaraland mole-rats do not need groups to survive and that cooperative breeding in the species is not obligate as pairs can-and frequently do-reproduce without the assistance of helpers. While re-emphasizing the importance of ecological constraints on dispersal in social mole-rats, the mixed effects of group size in our study suggest that indirect benefits accrued through cooperative behavior may have played a less prominent role in the evolution of mole-rat group-living than previously thought.
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Affiliation(s)
- Jack Thorley
- Corresponding author: Department of Zoology, Downing Street, University of Cambridge, Cambridge, CB2 3EJ, United Kingdom.
| | | | - Kyle Finn
- Kalahari Research Centre, Kuruman River Reserve, Van Zylsrus, South Africa
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, South Africa
| | - Tim Clutton-Brock
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
- Kalahari Research Centre, Kuruman River Reserve, Van Zylsrus, South Africa
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, South Africa
| | - Markus Zöttl
- Kalahari Research Centre, Kuruman River Reserve, Van Zylsrus, South Africa
- Department of Biology and Environmental Science, Linnaeus University, Kalmar, Sweden
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4
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García-Ruiz I, Taborsky M. Group augmentation on trial: helpers in small groups enhance antipredator defence of eggs. Biol Lett 2022; 18:20220170. [PMID: 36196551 PMCID: PMC9533001 DOI: 10.1098/rsbl.2022.0170] [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: 03/31/2022] [Accepted: 09/06/2022] [Indexed: 11/12/2022] Open
Abstract
Mechanisms selecting for the evolution of cooperative breeding are hotly debated. While kin selection theory has been the central paradigm to explain the seemingly altruistic behaviour of non-reproducing helpers, it is increasingly recognized that direct fitness benefits may be highly relevant. The group augmentation hypothesis proposes that alloparental care may evolve to enhance group size when larger groups yield increased survival and/or reproductive success. However, there is a lack of empirical tests. Here we use the cooperatively breeding cichlid fish Neolamprologus pulcher, in which group size predicts survival and group stability, to test this hypothesis experimentally by prompting two cooperative tasks: defence against an egg predator and digging out sand from the breeding shelter. We controlled for alternative mechanisms such as kin selection, load lightening and coercion. As predicted by the group augmentation hypothesis, helpers increased defence against an egg predator in small compared with large groups. This difference was only evident in large helpers owing to size-specific task specialization. Furthermore, helpers showed more digging effort in the breeding chamber compared with alternative personal shelters, indicating that digging is an altruistic service to the dominant breeders.
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Affiliation(s)
- Irene García-Ruiz
- Division of Behavioural Ecology, Institute of Ecology and Evolution, University of Bern, CH-3032 Hinterkappelen, Switzerland
| | - Michael Taborsky
- Division of Behavioural Ecology, Institute of Ecology and Evolution, University of Bern, CH-3032 Hinterkappelen, Switzerland
- Max Planck Institute of Animal Behavior, D-78467 Konstanz, Germany
- Institute for Advanced Study (Wissenschaftskolleg) Berlin, D-14193 Berlin, Germany
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5
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Zöttl M, Bensch HM, Finn KT, Hart DW, Thorley J, Bennett NC, Braude S. Capture Order Across Social Bathyergids Indicates Similarities in Division of Labour and Spatial Organisation. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.877221] [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
The social mole-rats of the family Bathyergidae show elaborate social organisation that may include division of labour between breeders and non-breeders as well as across non-breeders within their groups. However, comparative behavioural data across the taxa are rare and contrasts and similarities between species are poorly understood. Field studies of social bathyergids usually involve capturing all group members until the entire group is captured. Because each animal is only captured once and traps are typically placed in close proximity to active foraging areas, the order in which animals are captured provides an indication of the foraging activity of different individuals and of the spatial organisation of the group within the burrow system. Here, we compare the association of capture order with breeding status, sex, and body mass in four species and subspecies of social bathyergids, which vary in group size and represent all three social genera within the family Bathyergidae. We show that in naked and Damaraland mole-rats (Heterocephalus glaber and Fukomys damarensis), male and female breeders are captured later than non-breeders, whereas in two different subspecies of the genus Cryptomys only female breeders are captured later than non-breeders. The effect sizes vary largely and are 10 times larger in naked mole-rats as compared to Fukomys and 3–4 times larger than in Cryptomys. Among non-breeders, sex effects are notably absent in all species and body mass predicted capture order in both naked and Damaraland mole-rats. In naked mole-rats, larger non-breeders were captured earlier than smaller ones, whereas in Damaraland mole-rats intermediate-sized non-breeders were captured first. Our data suggest that there are similarities in behavioural structure and spatial organisation across all social bathyergid species, though the most pronounced differences within groups are found in naked mole-rats.
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Josi D, Heg D, Takeyama T, Bonfils D, Konovalov DA, Frommen JG, Kohda M, Taborsky M. Age- and sex-dependent variation in relatedness corresponds to reproductive skew, territory inheritance, and workload in cooperatively breeding cichlids. Evolution 2021; 75:2881-2897. [PMID: 34555177 PMCID: PMC9298395 DOI: 10.1111/evo.14348] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 07/27/2021] [Accepted: 08/18/2021] [Indexed: 11/28/2022]
Abstract
Kin selection plays a major role in the evolution of cooperative systems. However, many social species exhibit complex within-group relatedness structures, where kin selection alone cannot explain the occurrence of cooperative behavior. Understanding such social structures is crucial to elucidate the evolution and maintenance of multi-layered cooperative societies. In lamprologine cichlids, intragroup relatedness seems to correlate positively with reproductive skew, suggesting that in this clade dominants tend to provide reproductive concessions to unrelated subordinates to secure their participation in brood care. We investigate how patterns of within-group relatedness covary with direct and indirect fitness benefits of cooperation in a highly social vertebrate, the cooperatively breeding, polygynous lamprologine cichlid Neolamprologus savoryi. Behavioral and genetic data from 43 groups containing 578 individuals show that groups are socially and genetically structured into subgroups. About 17% of group members were unrelated immigrants, and average relatedness between breeders and brood care helpers declined with helper age due to group membership dynamics. Hence the relative importance of direct and indirect fitness benefits of cooperation depends on helper age. Our findings highlight how both direct and indirect fitness benefits of cooperation and group membership can select for cooperative behavior in societies comprising complex social and relatedness structures.
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Affiliation(s)
- Dario Josi
- Division of Behavioural Ecology, Institute of Ecology and Evolution, University of Bern, Hinterkappelen, Switzerland.,Conservation, Ecology, Evolution and Behaviour Research Group, Ecology and Environment Research Centre, Department of Natural Sciences, Manchester Metropolitan University, Manchester, UK
| | - Dik Heg
- Division of Behavioural Ecology, Institute of Ecology and Evolution, University of Bern, Hinterkappelen, Switzerland.,CTU Bern, University of Bern, Bern, Switzerland
| | - Tomohiro Takeyama
- Department of Biosphere-Geosphere Science, Okayama University of Science, Okayama, Japan.,Department of Biology and Geosciences, Graduate School of Science, Osaka City University, Osaka, Japan
| | - Danielle Bonfils
- Division of Behavioural Ecology, Institute of Ecology and Evolution, University of Bern, Hinterkappelen, Switzerland
| | - Dmitry A Konovalov
- College of Science and Engineering, James Cook University, Townsville, Australia
| | - Joachim G Frommen
- Division of Behavioural Ecology, Institute of Ecology and Evolution, University of Bern, Hinterkappelen, Switzerland.,Conservation, Ecology, Evolution and Behaviour Research Group, Ecology and Environment Research Centre, Department of Natural Sciences, Manchester Metropolitan University, Manchester, UK
| | - Masanori Kohda
- Department of Biology and Geosciences, Graduate School of Science, Osaka City University, Osaka, Japan
| | - Michael Taborsky
- Division of Behavioural Ecology, Institute of Ecology and Evolution, University of Bern, Hinterkappelen, Switzerland
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7
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Affiliation(s)
- Gerald G. Carter
- Department of Evolution, Ecology, and Organismal Biology The Ohio State University Columbus OH USA
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8
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Barve S, Riehl C, Walters EL, Haydock J, Dugdale HL, Koenig WD. Lifetime reproductive benefits of cooperative polygamy vary for males and females in the acorn woodpecker ( Melanerpes formicivorus). Proc Biol Sci 2021; 288:20210579. [PMID: 34403633 PMCID: PMC8370801 DOI: 10.1098/rspb.2021.0579] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 07/22/2021] [Indexed: 11/12/2022] Open
Abstract
Cooperative breeding strategies lead to short-term direct fitness losses when individuals forfeit or share reproduction. The direct fitness benefits of cooperative strategies are often delayed and difficult to quantify, requiring data on lifetime reproduction. Here, we use a longitudinal dataset to examine the lifetime reproductive success of cooperative polygamy in acorn woodpeckers (Melanerpes formicivorus), which nest as lone pairs or share reproduction with same-sex cobreeders. We found that males and females produced fewer young per successful nesting attempt when sharing reproduction. However, males nesting in duos and trios had longer reproductive lifespans, more lifetime nesting attempts and higher lifetime reproductive success than those breeding alone. For females, cobreeding in duos increased reproductive lifespan so the lifetime reproductive success of females nesting in duos was comparable to those nesting alone and higher than those nesting in trios. These results suggest that for male duos and trios, reproductive success alone may provide sufficient fitness benefits to explain the presence of cooperative polygamy, and the benefits of cobreeding as a duo in females are higher than previously assumed. Lifetime individual fitness data are crucial to reveal the full costs and benefits of cooperative polygamy.
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Affiliation(s)
- Sahas Barve
- Division of Birds, Smithsonian National Museum of Natural History, 10th Street and Constitution Avenue NW, Washington, DC 20560, USA
| | - Christina Riehl
- Department of Ecology and Evolutionary Biology, Princeton University, 106A Guyot Hall, Princeton, NJ 08544, USA
| | - Eric L. Walters
- Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, USA
| | - Joseph Haydock
- Department of Biology, Gonzaga University, Spokane, WA 99258, USA
| | - Hannah L. Dugdale
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen 9747 AG, The Netherlands
| | - Walter D. Koenig
- Hastings Reservation, University of California Berkeley, 38601 E. Carmel Valley Rd., Carmel Valley, CA 93924, USA
- Lab of Ornithology, Cornell University, 159 Sapsucker Woods Rd., Ithaca, NY 14850, USA
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9
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West SA, Cooper GA, Ghoul MB, Griffin AS. Ten recent insights for our understanding of cooperation. Nat Ecol Evol 2021; 5:419-430. [PMID: 33510431 PMCID: PMC7612052 DOI: 10.1038/s41559-020-01384-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 12/11/2020] [Indexed: 01/29/2023]
Abstract
Since Hamilton published his seminal papers in 1964, our understanding of the importance of cooperation for life on Earth has evolved beyond recognition. Early research was focused on altruism in the social insects, where the problem of cooperation was easy to see. In more recent years, research into cooperation has expanded across the entire tree of life, and has been revolutionized by advances in genetic, microbiological and analytical techniques. We highlight ten insights that have arisen from these advances, which have illuminated generalizations across different taxa, making the world simpler to explain. Furthermore, progress in these areas has opened up numerous new problems to solve, suggesting exciting directions for future research.
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Affiliation(s)
- Stuart A West
- Department of Zoology, University of Oxford, Oxford, UK.
| | - Guy A Cooper
- Department of Zoology, University of Oxford, Oxford, UK
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10
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Downing PA, Griffin AS, Cornwallis CK. Hard-working helpers contribute to long breeder lifespans in cooperative birds. Philos Trans R Soc Lond B Biol Sci 2021; 376:20190742. [PMID: 33678023 DOI: 10.1098/rstb.2019.0742] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In many species that raise young in cooperative groups, breeders live an exceptionally long time despite high investment in offspring production. How is this possible given the expected trade-off between survival and reproduction? One possibility is that breeders extend their lifespans by outsourcing parental care to non-reproductive group members. Having help lightens breeder workloads and the energy that is saved can be allocated to survival instead. We tested this hypothesis using phylogenetic meta-analysis across 23 cooperatively breeding bird species. We found that breeders with helpers had higher rates of annual survival than those without helpers (8% on average). Increased breeder survival was correlated with reduced investment in feeding offspring, which in turn depended on the proportion of feeding provided by helpers. Helpers had similar effects on female and male breeder survival. Our results indicate that one of the secrets to a long life is reduced investment in parental care. This appears to be a unique feature of cooperative societies with hard-working helpers. This article is part of the theme issue 'Ageing and sociality: why, when and how does sociality change ageing patterns?'
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11
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Nest defence and offspring provisioning in a cooperative bird: individual subordinates vary in total contribution, but no division of tasks among breeders and subordinates. Behav Ecol Sociobiol 2020. [DOI: 10.1007/s00265-020-02877-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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12
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Pull CD, McMahon DP. Superorganism Immunity: A Major Transition in Immune System Evolution. Front Ecol Evol 2020. [DOI: 10.3389/fevo.2020.00186] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
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13
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Barve S, Hagemeyer NDG, Winter RE, Chamberlain SD, Koenig WD, Winkler DW, Walters EL. Wandering woodpeckers: foray behavior in a social bird. Ecology 2020; 101:e02943. [PMID: 31782526 DOI: 10.1002/ecy.2943] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 09/17/2019] [Accepted: 10/18/2019] [Indexed: 01/05/2023]
Abstract
In many cooperatively breeding taxa, nonbreeding subordinates, or helpers, use extra-territorial forays to discover dispersal opportunities. Such forays are considered energetically costly and foraying birds face aggression from conspecific members of the territories they visit. In contrast, breeders in cooperatively breeding taxa are expected to foray seldomly. We used novel tracking technologies to follow 62 acorn woodpeckers (Melanerpes formicivorus), a cooperatively breeding bird, to study extra-territorial foray behavior. Both helpers and breeders engaged in extra-territorial forays routinely and often several times per day. Helpers forayed earlier in the day and invested more time when foraying to high-quality territories. Unexpectedly, breeders forayed as often and as far as helpers. Breeders from high-quality territories forayed closer to their home territories than breeders from low-quality territories, reflecting a potential trade-off between foraying and territory defense. Such a routine pattern of extra-territorial forays in both helpers and breeders suggests that the motives behind forays differ by sex and social status and involve more than simply searching for dispersal opportunities.
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Affiliation(s)
- Sahas Barve
- Old Dominion University, Norfolk, Virginia, 23529, USA.,Hastings Natural History Reservation, University of California, Carmel Valley, California, 93924, USA.,National Museum of Natural History, Washington, District of Columbia, 20560, USA
| | | | | | | | - Walter D Koenig
- Hastings Natural History Reservation, University of California, Carmel Valley, California, 93924, USA.,Lab of Ornithology, Cornell University, Ithaca, New York, 14850, USA
| | - David W Winkler
- Department of Ecology and Evolutionary Biology and TABER, Cornell University, Ithaca, New York, 14853, USA.,Cellular Tracking Technologies, Rio Grande, New Jersey, 08242, USA.,Conservation Science Global, West Cape May, New Jersey, 08204, USA
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14
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Khwaja N, Massaro M, Martin TE, Briskie JV. Do Parents Synchronise Nest Visits as an Antipredator Adaptation in Birds of New Zealand and Tasmania? Front Ecol Evol 2019. [DOI: 10.3389/fevo.2019.00389] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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15
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Downing PA, Griffin AS, Cornwallis CK. Sex differences in helping effort reveal the effect of future reproduction on cooperative behaviour in birds. Proc Biol Sci 2018; 285:20181164. [PMID: 30135160 PMCID: PMC6125912 DOI: 10.1098/rspb.2018.1164] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2018] [Accepted: 07/25/2018] [Indexed: 01/06/2023] Open
Abstract
The evolution of helping behaviour in species that breed cooperatively in family groups is typically attributed to kin selection alone. However, in many species, helpers go on to inherit breeding positions in their natal groups, but the extent to which this contributes to selection for helping is unclear as the future reproductive success of helpers is often unknown. To quantify the role of future reproduction in the evolution of helping, we compared the helping effort of female and male retained offspring across cooperative birds. The kin selected benefits of helping are equivalent between female and male helpers-they are equally related to the younger siblings they help raise-but the future reproductive benefits of helping differ because of sex differences in the likelihood of breeding in the natal group. We found that the sex which is more likely to breed in its natal group invests more in helping, suggesting that in addition to kin selection, helping in family groups is shaped by future reproduction.
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