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Meniri M, Evans E, Thompson FJ, Marshall HH, Nichols HJ, Lewis G, Holt L, Davey E, Mitchell C, Johnstone RA, Cant MA, Blount JD. Untangling the oxidative cost of reproduction: An analysis in wild banded mongooses. Ecol Evol 2022; 12:e8644. [PMID: 35342583 PMCID: PMC8928901 DOI: 10.1002/ece3.8644] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 01/15/2022] [Indexed: 02/02/2023] Open
Abstract
The cost of reproduction plays a central role in evolutionary theory, but the identity of the underlying mechanisms remains a puzzle. Oxidative stress has been hypothesized to be a proximate mechanism that may explain the cost of reproduction. We examine three pathways by which oxidative stress could shape reproduction. The “oxidative cost” hypothesis proposes that reproductive effort generates oxidative stress, while the “oxidative constraint” and “oxidative shielding” hypotheses suggest that mothers mitigate such costs through reducing reproductive effort or by pre‐emptively decreasing damage levels, respectively. We tested these three mechanisms using data from a long‐term food provisioning experiment on wild female banded mongooses (Mungos mungo). Our results show that maternal supplementation did not influence oxidative stress levels, or the production and survival of offspring. However, we found that two of the oxidative mechanisms co‐occur during reproduction. There was evidence of an oxidative challenge associated with reproduction that mothers attempted to mitigate by reducing damage levels during breeding. This mitigation is likely to be of crucial importance, as long‐term offspring survival was negatively impacted by maternal oxidative stress. This study demonstrates the value of longitudinal studies of wild animals in order to highlight the interconnected oxidative mechanisms that shape the cost of reproduction.
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Affiliation(s)
- Magali Meniri
- College of Life & Environmental Sciences Centre for Ecology & Conservation University of Exeter Penryn UK
| | - Elsa Evans
- College of Life & Environmental Sciences Centre for Ecology & Conservation University of Exeter Penryn UK
| | - Faye J. Thompson
- College of Life & Environmental Sciences Centre for Ecology & Conservation University of Exeter Penryn UK
| | - Harry H. Marshall
- College of Life & Environmental Sciences Centre for Ecology & Conservation University of Exeter Penryn UK
- Whitelands College Centre for Research in Ecology, Evolution & Behaviour University of Roehampton London UK
| | | | - Gina Lewis
- Department of Biosciences Swansea University Swansea UK
| | - Lauren Holt
- College of Life & Environmental Sciences Centre for Ecology & Conservation University of Exeter Penryn UK
| | - Emma Davey
- College of Life & Environmental Sciences Centre for Ecology & Conservation University of Exeter Penryn UK
| | - Christopher Mitchell
- College of Life & Environmental Sciences Centre for Ecology & Conservation University of Exeter Penryn UK
| | | | - Michael A. Cant
- College of Life & Environmental Sciences Centre for Ecology & Conservation University of Exeter Penryn UK
| | - Jonathan D. Blount
- College of Life & Environmental Sciences Centre for Ecology & Conservation University of Exeter Penryn UK
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2
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A veil of ignorance can promote fairness in a mammal society. Nat Commun 2021; 12:3717. [PMID: 34162841 PMCID: PMC8222408 DOI: 10.1038/s41467-021-23910-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 05/10/2021] [Indexed: 11/29/2022] Open
Abstract
Rawls argued that fairness in human societies can be achieved if decisions about the distribution of societal rewards are made from behind a veil of ignorance, which obscures the personal gains that result. Whether ignorance promotes fairness in animal societies, that is, the distribution of resources to reduce inequality, is unknown. Here we show experimentally that cooperatively breeding banded mongooses, acting from behind a veil of ignorance over kinship, allocate postnatal care in a way that reduces inequality among offspring, in the manner predicted by a Rawlsian model of cooperation. In this society synchronized reproduction leaves adults in a group ignorant of the individual parentage of their communal young. We provisioned half of the mothers in each mongoose group during pregnancy, leaving the other half as matched controls, thus increasing inequality among mothers and increasing the amount of variation in offspring birth weight in communal litters. After birth, fed mothers provided extra care to the offspring of unfed mothers, not their own young, which levelled up initial size inequalities among the offspring and equalized their survival to adulthood. Our findings suggest that a classic idea of moral philosophy also applies to the evolution of cooperation in biological systems. Obscuring knowledge of personal gains from individuals can theoretically maintain fairness in a cooperative group. Experiments show that wild, cooperatively breeding banded mongooses uncertain of kinship allocate postnatal care in a way that reduces inequality among offspring, suggesting a classic idea of moral philosophy can apply in biological systems.
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3
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Hobson L, Hurst JL, Stockley P. Increased sperm production linked to competition in the maternal social environment. ROYAL SOCIETY OPEN SCIENCE 2020; 7:201171. [PMID: 33489271 PMCID: PMC7813238 DOI: 10.1098/rsos.201171] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 11/20/2020] [Indexed: 06/12/2023]
Abstract
Maternal or early life effects may prepare offspring for similar social conditions to those experienced by their mothers. For males, the ability to achieve mating and fertilization success is a key social challenge. Competitive conditions may therefore favour increased body size or ejaculate production in male offspring. We tested this experimentally by comparing reproductive traits of adult male bank voles (Myodes glareolus), whose mothers had experienced contrasting encounter regimes with female conspecifics while breeding. We found that daily sperm production rates and epididymis mass were significantly higher when dams had experienced more frequent encounters with female conspecifics. This response to maternal and early life experience was specific to sperm production and storage, with no evidence for effects on male body mass or the size of testes and accessory reproductive glands. Our findings reveal a potentially adaptive effect of maternal and early life experience on the development of sperm production, which is worthy of wider investigation.
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4
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Use of a portable ultrasound machine to determine pregnancy and uterine litter size for wild Gunnison’s prairie dogs (Cynomys gunnisoni). MAMMAL RES 2020. [DOI: 10.1007/s13364-020-00530-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Wells JCK. Developmental plasticity as adaptation: adjusting to the external environment under the imprint of maternal capital. Philos Trans R Soc Lond B Biol Sci 2020; 374:20180122. [PMID: 30966888 DOI: 10.1098/rstb.2018.0122] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Plasticity is assumed to enable beneficial adjustment to the environment. In this context, developmental plasticity is generally approached within a two-stage framework, whereby adjustments to ecological cues in stage 1 are exposed to selection in stage 2. This conceptual approach may have limitations, because in species providing parental investment, particularly placental mammals such as humans, initial adjustments are not to the environment directly, but rather to the niche generated by parental phenotype (in mammals, primarily that of the mother). Only as maternal investment is withdrawn is the developing organism exposed directly to prevailing ecological conditions. A three-stage model may therefore be preferable, where developmental trajectory first adjusts to maternal investment, then to the external environment. Each offspring experiences a trade-off, benefitting from maternal investment during the most vulnerable stages of development, at the cost of exposure to investment strategies that maximize maternal fitness. Maternal life-history trade-offs impact the magnitude and schedule of her investment in her offspring, generating lifelong effects on traits related to health outcomes. Understanding the imprint of maternal capital on offspring is particularly important in species demonstrating social hierarchy. Interventions targeting maternal capital might offer new opportunities to improve health outcomes of both mother and offspring. This article is part of the theme issue 'Developing differences: early-life effects and evolutionary medicine'.
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Affiliation(s)
- Jonathan C K Wells
- Childhood Nutrition Research Centre, UCL Great Ormond Street Institute of Child Health , 30 Guilford Street, London WC 1N 1EH , UK
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6
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Inzani E, Marshall HH, Thompson FJ, Kalema-Zikusoka G, Cant MA, Vitikainen EIK. Spontaneous abortion as a response to reproductive conflict in the banded mongoose. Biol Lett 2019; 15:20190529. [PMID: 31795853 DOI: 10.1098/rsbl.2019.0529] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
When breeding females compete for limited resources, the intensity of this reproductive conflict can determine whether the fitness benefits of current reproductive effort exceed the potential costs to survival and future fertility. In group-living species, reproductive competition can occur through post-natal competition among the offspring of co-breeding females. Spontaneous abortion could be a response to such competition, allowing females to curtail reproductive expenditure on offspring that are unlikely to survive and to conserve resources for future breeding opportunities. We tested this hypothesis using long-term data on banded mongooses, Mungos mungo, in which multiple females within a group give birth synchronously to a communal litter that is cared for by other group members. As predicted, abortions were more likely during dry periods when food is scarce, and in breeding attempts with more intense reproductive competition. Within breeding events, younger, lighter females carrying smaller fetuses were more likely to abort, particularly those that were also of lower rank. Our results suggest that abortion may be a means by which disadvantaged females conserve resources for future breeding attempts in more benign conditions, and highlight that female reproductive competition may be resolved long before the production of offspring.
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Affiliation(s)
- E Inzani
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, UK
| | - H H Marshall
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, UK.,Centre for Research in Ecology, Evolution and Behaviour, University of Roehampton, London, UK
| | - F J Thompson
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, UK
| | | | - M A Cant
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, UK
| | - E I K Vitikainen
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, UK.,Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
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Vitikainen EIK, Thompson FJ, Marshall HH, Cant MA. Live long and prosper: durable benefits of early-life care in banded mongooses. Philos Trans R Soc Lond B Biol Sci 2019; 374:20180114. [PMID: 30966878 PMCID: PMC6460079 DOI: 10.1098/rstb.2018.0114] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/31/2018] [Indexed: 12/24/2022] Open
Abstract
Kin selection theory defines the conditions for which altruism or 'helping' can be favoured by natural selection. Tests of this theory in cooperatively breeding animals have focused on the short-term benefits to the recipients of help, such as improved growth or survival to adulthood. However, research on early-life effects suggests that there may be more durable, lifelong fitness impacts to the recipients of help, which in theory should strengthen selection for helping. Here, we show in cooperatively breeding banded mongooses ( Mungos mungo) that care received in the first 3 months of life has lifelong fitness benefits for both male and female recipients. In this species, adult helpers called 'escorts' form exclusive one-to-one caring relationships with specific pups (not their own offspring), allowing us to isolate the effects of being escorted on later reproduction and survival. Pups that were more closely escorted were heavier at sexual maturity, which was associated with higher lifetime reproductive success for both sexes. Moreover, for female offspring, lifetime reproductive success increased with the level of escorting received per se, over and above any effect on body mass. Our results suggest that early-life social care has durable benefits to offspring of both sexes in this species. Given the well-established developmental effects of early-life care in laboratory animals and humans, we suggest that similar effects are likely to be widespread in social animals more generally. We discuss some of the implications of durable fitness benefits for the evolution of intergenerational helping in cooperative animal societies, including humans. This article is part of the theme issue 'Developing differences: early-life effects and evolutionary medicine'.
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Affiliation(s)
- Emma I. K. Vitikainen
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, UK
- Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Faye J. Thompson
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, UK
| | - Harry H. Marshall
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, UK
- Department of Life Sciences, University of Roehampton, London, UK
| | - Michael A. Cant
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, UK
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Vitikainen EIK, Marshall HH, Thompson FJ, Sanderson JL, Bell MBV, Gilchrist JS, Hodge SJ, Nichols HJ, Cant MA. Biased escorts: offspring sex, not relatedness explains alloparental care patterns in a cooperative breeder. Proc Biol Sci 2018; 284:rspb.2016.2384. [PMID: 28469015 PMCID: PMC5443930 DOI: 10.1098/rspb.2016.2384] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 04/11/2017] [Indexed: 11/12/2022] Open
Abstract
Kin selection theory predicts that animals should direct costly care where inclusive fitness gains are highest. Individuals may achieve this by directing care at closer relatives, yet evidence for such discrimination in vertebrates is equivocal. We investigated patterns of cooperative care in banded mongooses, where communal litters are raised by adult 'escorts' who form exclusive caring relationships with individual pups. We found no evidence that escorts and pups assort by parentage or relatedness. However, the time males spent escorting increased with increasing relatedness to the other group members, and to the pup they had paired with. Thus, we found no effect of relatedness in partner choice, but (in males) increasing helping effort with relatedness once partner choices had been made. Unexpectedly, the results showed clear assortment by sex, with female carers being more likely to tend to female pups, and male carers to male pups. This sex-specific assortment in helping behaviour has potential lifelong impacts on individual development and may impact the future size and composition of natal groups and dispersing cohorts. Where relatedness between helpers and recipients is already high, individuals may be better off choosing partners using other predictors of the costs and benefits of cooperation, without the need for possibly costly within-group kin discrimination.
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Affiliation(s)
- Emma I K Vitikainen
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, UK
| | - Harry H Marshall
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, UK
| | - Faye J Thompson
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, UK
| | - Jenni L Sanderson
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, UK
| | - Matthew B V Bell
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK
| | - Jason S Gilchrist
- School of Applied Sciences, Edinburgh Napier University, Edinburgh, UK
| | - Sarah J Hodge
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, UK
| | - Hazel J Nichols
- School of Natural Sciences and Psychology, Liverpool John Moores University, Liverpool L3 3AF, UK
| | - Michael A Cant
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, UK
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Woelber BK, Hall CL, Howard DR. Environmental cues influence parental brood structure decisions in the burying beetle Nicrophorus marginatus. J ETHOL 2017. [DOI: 10.1007/s10164-017-0527-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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10
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Explaining negative kin discrimination in a cooperative mammal society. Proc Natl Acad Sci U S A 2017; 114:5207-5212. [PMID: 28439031 DOI: 10.1073/pnas.1612235114] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Kin selection theory predicts that, where kin discrimination is possible, animals should typically act more favorably toward closer genetic relatives and direct aggression toward less closely related individuals. Contrary to this prediction, we present data from an 18-y study of wild banded mongooses, Mungos mungo, showing that females that are more closely related to dominant individuals are specifically targeted for forcible eviction from the group, often suffering severe injury, and sometimes death, as a result. This pattern cannot be explained by inbreeding avoidance or as a response to more intense local competition among kin. Instead, we use game theory to show that such negative kin discrimination can be explained by selection for unrelated targets to invest more effort in resisting eviction. Consistent with our model, negative kin discrimination is restricted to eviction attempts of older females capable of resistance; dominants exhibit no kin discrimination when attempting to evict younger females, nor do they discriminate between more closely or less closely related young when carrying out infanticidal attacks on vulnerable infants who cannot defend themselves. We suggest that in contexts where recipients of selfish acts are capable of resistance, the usual prediction of positive kin discrimination can be reversed. Kin selection theory, as an explanation for social behavior, can benefit from much greater exploration of sequential social interactions.
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Marshall HH, Vitikainen EIK, Mwanguhya F, Businge R, Kyabulima S, Hares MC, Inzani E, Kalema-Zikusoka G, Mwesige K, Nichols HJ, Sanderson JL, Thompson FJ, Cant MA. Lifetime fitness consequences of early-life ecological hardship in a wild mammal population. Ecol Evol 2017; 7:1712-1724. [PMID: 28331582 PMCID: PMC5355200 DOI: 10.1002/ece3.2747] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 12/01/2016] [Accepted: 12/22/2016] [Indexed: 12/11/2022] Open
Abstract
Early-life ecological conditions have major effects on survival and reproduction. Numerous studies in wild systems show fitness benefits of good quality early-life ecological conditions ("silver-spoon" effects). Recently, however, some studies have reported that poor-quality early-life ecological conditions are associated with later-life fitness advantages and that the effect of early-life conditions can be sex-specific. Furthermore, few studies have investigated the effect of the variability of early-life ecological conditions on later-life fitness. Here, we test how the mean and variability of early-life ecological conditions affect the longevity and reproduction of males and females using 14 years of data on wild banded mongooses (Mungos mungo). Males that experienced highly variable ecological conditions during development lived longer and had greater lifetime fitness, while those that experienced poor early-life conditions lived longer but at a cost of reduced fertility. In females, there were no such effects. Our study suggests that exposure to more variable environments in early life can result in lifetime fitness benefits, whereas differences in the mean early-life conditions experienced mediate a life-history trade-off between survival and reproduction. It also demonstrates how early-life ecological conditions can produce different selection pressures on males and females.
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Affiliation(s)
- Harry H Marshall
- Centre for Ecology and Conservation University of Exeter Cornwall UK
| | | | - Francis Mwanguhya
- Banded Mongoose Research Project Queen Elizabeth National Park Kasese District Uganda
| | - Robert Businge
- Banded Mongoose Research Project Queen Elizabeth National Park Kasese District Uganda
| | - Solomon Kyabulima
- Banded Mongoose Research Project Queen Elizabeth National Park Kasese District Uganda
| | - Michelle C Hares
- Centre for Ecology and Conservation University of Exeter Cornwall UK
| | - Emma Inzani
- Centre for Ecology and Conservation University of Exeter Cornwall UK
| | | | - Kenneth Mwesige
- Banded Mongoose Research Project Queen Elizabeth National Park Kasese District Uganda
| | - Hazel J Nichols
- School of Natural Science and Psychology Liverpool John Moores University Liverpool UK
| | | | - Faye J Thompson
- Centre for Ecology and Conservation University of Exeter Cornwall UK
| | - Michael A Cant
- Centre for Ecology and Conservation University of Exeter Cornwall UK
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