1
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Kappeler PM, Benhaiem S, Fichtel C, Fromhage L, Höner OP, Jennions MD, Kaiser S, Krüger O, Schneider JM, Tuni C, van Schaik J, Goymann W. Sex roles and sex ratios in animals. Biol Rev Camb Philos Soc 2023; 98:462-480. [PMID: 36307924 DOI: 10.1111/brv.12915] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 10/12/2022] [Accepted: 10/14/2022] [Indexed: 11/29/2022]
Abstract
In species with separate sexes, females and males often differ in their morphology, physiology and behaviour. Such sex-specific traits are functionally linked to variation in reproductive competition, mate choice and parental care, which have all been linked to sex roles. At the 150th anniversary of Darwin's theory on sexual selection, the question of why patterns of sex roles vary within and across species remains a key topic in behavioural and evolutionary ecology. New theoretical, experimental and comparative evidence suggests that variation in the adult sex ratio (ASR) is a key driver of variation in sex roles. Here, we first define and discuss the historical emergence of the sex role concept, including recent criticisms and rebuttals. Second, we review the various sex ratios with a focus on ASR, and explore its theoretical links to sex roles. Third, we explore the causes, and especially the consequences, of biased ASRs, focusing on the results of correlational and experimental studies of the effect of ASR variation on mate choice, sexual conflict, parental care and mating systems, social behaviour, hormone physiology and fitness. We present evidence that animals in diverse societies are sensitive to variation in local ASR, even on short timescales, and propose explanations for conflicting results. We conclude with an overview of open questions in this field integrating demography, life history and behaviour.
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Affiliation(s)
- Peter M Kappeler
- Behavioral Ecology and Sociobiology Unit, German Primate Center - Leibniz Institute of Primatology, Kellnerweg 4, 37077, Göttingen, Germany
- Department of Sociobiology/Anthropology, University of Göttingen, Kellnerweg 6, 37077, Göttingen, Germany
| | - Sarah Benhaiem
- Department of Ecological Dynamics, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Strasse 17, D-10315, Berlin, Germany
| | - Claudia Fichtel
- Behavioral Ecology and Sociobiology Unit, German Primate Center - Leibniz Institute of Primatology, Kellnerweg 4, 37077, Göttingen, Germany
| | - Lutz Fromhage
- Department of Biological and Environmental Science, Ambiotica, University of Jyväskylä, PO Box 35, 40014, Jyväskylä, Finland
| | - Oliver P Höner
- Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Strasse 17, D-10315, Berlin, Germany
| | - Michael D Jennions
- Division of Ecology & Evolution, Research School of Biology, ANU College of Science, The Australian National University, RN Robertson Building, 46 Sullivans Creek Road, Canberra, ACT, 2600, Australia
| | - Sylvia Kaiser
- Department of Behavioural Biology, University of Münster, Badestr. 13, 48149, Münster, Germany
| | - Oliver Krüger
- Department of Animal Behavior, Bielefeld University, Morgenbreede 45, 33615, Bielefeld, Germany
| | - Jutta M Schneider
- Department of Biology, Institute of Zoology, Universität Hamburg, Martin-Luther-King Platz 3, 20146, Hamburg, Germany
| | - Cristina Tuni
- Department of Biology II, Ludwig Maximilians University of Munich, Großhaderner Str 2, 82152, Planegg-Martinsried, Germany
| | - Jaap van Schaik
- Applied Zoology and Nature Conservation, University of Greifswald, Loitzer Str. 26, 17489, Greifswald, Germany
| | - Wolfgang Goymann
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, Eberhard-Gwinner-Str. 6a, D-82319, Seewiesen, Germany
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2
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The significant role of post-pairing male behavior on the evolution of male preferences and female traits. Commun Biol 2022; 5:4. [PMID: 35013514 PMCID: PMC8748628 DOI: 10.1038/s42003-021-02961-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 12/09/2021] [Indexed: 11/24/2022] Open
Abstract
Existing sexual selection theory postulates that a sufficiently large variation in female fecundity or other direct benefits are fundamental for generating male mate choice. In this study, we suggest that, in addition to pre-pairing preferences, choosy males can also have different post-pairing behaviors, a factor which has been comparatively overlooked by previous studies. We found that both male preferences and female traits could evolve much more easily than previously expected when the choosy males that paired with unpreferred females would allocate more efforts to seeking additional post-pairing mating opportunities. Furthermore, a costly female trait could evolve when there was a trade-off between seeking additional mating and paternal care investment within social pair for choosy males. Finally, a costly male preference and a costly female trait might still evolve and reach a stable polymorphic state in the population, which might give rise to a high variability in male choice and female traits in nature. We suggest that male mate choice may be even more common than expected, which needs to be verified empirically. Lyu and colleagues use theoretical models to examine the relationship between post-pairing male behaviors and female trait evolution. They find that male mate choosiness can be surprisingly influential on the evolution of costly female traits, but also that costly male preference and costly female traits could evolve to a polymorphic equilibrium under certain conditions.
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3
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Garcia de la Chica A, Wood DB, Rotundo M, Fernandez‐Duque E. Responses of a pair‐living, sexually monogamous primate to the simulated presence of solitary individuals: A field playback experiment. Ethology 2021. [DOI: 10.1111/eth.13222] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
| | - David Bechtel Wood
- Owl Monkey Project‐ Fundación ECO Formosa Argentina
- Yale University New Haven Connecticut USA
| | | | - Eduardo Fernandez‐Duque
- Owl Monkey Project‐ Fundación ECO Formosa Argentina
- Yale University New Haven Connecticut USA
- Universidad de Formosa Formosa Argentina
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4
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Parker GA. Conceptual developments in sperm competition: a very brief synopsis. Philos Trans R Soc Lond B Biol Sci 2020; 375:20200061. [PMID: 33070727 DOI: 10.1098/rstb.2020.0061] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The past half century has seen the development of the field of post-ejaculatory sexual selection, the sequel to sexual selection for mate-acquisition (pre-ejaculatory) described by Darwin. In richness and diversity of adaptations, post-ejaculatory selection rivals that of pre-ejaculatory sexual selection. Anisogamy-and hence two sexes-likely arose by primeval gamete competition, and sperm competition remains a major force maintaining high sperm numbers. The post-ejaculatory equivalent of male-male competition for matings, sperm competition was an intense ancestral form of sexual selection, typically weakening as mobility and internal fertilization developed in many taxa, when some expenditure became diverted into pre-ejaculatory competition. Sperm competition theory has been relatively successful in explaining variation in relative testes size and sperm numbers per ejaculate and is becoming more successful in explaining variation in sperm phenotype. Sperm competition has generated many other male adaptations such as seminal fluid proteins that variously modify female reproduction towards male interests, and copulatory plugs, prolonged copulations and post-ejaculatory guarding behaviour that reduce female remating probability, many of which result in sexual conflict. This short survey of conceptual developments is intended as a broad overview, mainly as a primer for new researchers. This article is part of the theme issue 'Fifty years of sperm competition'.
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Affiliation(s)
- Geoff A Parker
- Department of Evolution, Ecology and Behaviour, University of Liverpool, Biosciences Building, Crown Street, Liverpool L69 7ZB, UK
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5
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Fernandez-Duque E, Huck M, Van Belle S, Di Fiore A. The evolution of pair-living, sexual monogamy, and cooperative infant care: Insights from research on wild owl monkeys, titis, sakis, and tamarins. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 171 Suppl 70:118-173. [PMID: 32191356 DOI: 10.1002/ajpa.24017] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2019] [Revised: 12/18/2019] [Accepted: 12/20/2019] [Indexed: 12/28/2022]
Abstract
"Monogamy" and pair bonding have long been of interest to anthropologists and primatologists. Their study contributes to our knowledge of human evolutionary biology and social evolution without the cultural trappings associated with studying human societies directly. Here, we first provide an overview of theoretical considerations, followed by an evaluation of recent comparative studies of the evolution of "social monogamy"; we are left with serious doubts about the conclusions of these studies that stem from the often poor quality of the data used and an overreliance on secondary sources without vetting the data therein. We then describe our field research program on four "monogamous" platyrrhines (owl monkeys, titis, sakis, and tamarins), evaluate how well our data support various hypotheses proposed to explain "monogamy," and compare our data to those reported on the same genera in comparative studies. Overall, we found a distressing lack of agreement between the data used in comparative studies and data from the literature for the taxa that we work with. In the final section, we propose areas of research that deserve more attention. We stress the need for more high-quality natural history data, and we urge researchers to be cautious about the uncritical use of variables of uncertain internal validity. Overall, it is imperative that biological anthropologists establish and follow clear criteria for comparing and combining results from published studies and that researchers, reviewers, and editors alike comply with these standards to improve the transparency, reproducibility, and interpretability of causal inferences made in comparative studies.
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Affiliation(s)
- Eduardo Fernandez-Duque
- Department of Anthropology, Yale University, New Haven, Connecticut.,Owl Monkey Project, Fundación ECO, Formosa, Argentina.,Facultad de Recursos Naturales, Universidad Nacional de Formosa, Formosa, Argentina.,College of Biological and Environmental Sciences, Universidad San Francisco de Quito, Quito, Ecuador
| | - Maren Huck
- School of Environmental Sciences, University of Derby, Derby, UK
| | - Sarie Van Belle
- Department of Anthropology, University of Texas, Austin, Texas.,Primate Molecular Ecology and Evolution Laboratory, University of Texas, Austin, Texas
| | - Anthony Di Fiore
- College of Biological and Environmental Sciences, Universidad San Francisco de Quito, Quito, Ecuador.,Department of Anthropology, University of Texas, Austin, Texas.,Primate Molecular Ecology and Evolution Laboratory, University of Texas, Austin, Texas
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6
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Huck M, Di Fiore A, Fernandez-Duque E. Of Apples and Oranges? The Evolution of “Monogamy” in Non-human Primates. Front Ecol Evol 2020. [DOI: 10.3389/fevo.2019.00472] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
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7
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McCambridge JE, Walker LA, Holwell GI. Natural history and ecology of the New Zealand sheet-web spiders Cambridgea plagiata and C. foliata (Araneae: Desidae). J NAT HIST 2019. [DOI: 10.1080/00222933.2019.1632951] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
| | - Leilani A. Walker
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Gregory I. Holwell
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
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8
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Polyandrous bee provides extended offspring care biparentally as an alternative to monandry based eusociality. Proc Natl Acad Sci U S A 2019; 116:6238-6243. [PMID: 30858313 DOI: 10.1073/pnas.1810092116] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Parental care behavior evolves to increase the survival of offspring. When offspring care becomes complicated for ecological reasons, cooperation of multiple individuals can be beneficial. There are two types of cooperative care: biparental care and worker (helper)-based care (e.g., eusociality). Although biparental care is common in several groups of vertebrates, it is generally rare in arthropods. Conversely, eusociality is widespread in insects, especially the aculeate Hymenoptera. Here, we present a case of biparental care in bees, in Ceratina nigrolabiata (Apidae, Xylocopinae). Similar to eusocial behavior, biparental care leads to greater brood protection in this species. Male guarding increases provisioning of nests because females are liberated from the tradeoff between provisioning and nest protection. The main benefit of parental care for males should be increased paternity. Interestingly though, we found that paternity of offspring by guard males is extraordinarily low (10% of offspring). Generally, we found that nests were not guarded by the same male for the whole provisioning season, meaning that males arrive to nests as stepfathers. However, we show that long-term guarding performed by a single male does increase paternity. We suggest that the multiple-mating strategy of these bees increased the amount of time for interactions between the sexes, and this longer period of potential interaction supported the origin of biparental care. Eusociality based on monandry was thought to be the main type of extended brood protection in bees. We show that biparental care based on polyandry provides an interesting evolutionary alternative.
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9
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Rice MA, Restrepo LF, Ophir AG. When to Cheat: Modeling Dynamics of Paternity and Promiscuity in Socially Monogamous Prairie Voles ( Microtus ochrogaster). Front Ecol Evol 2018; 6. [PMID: 34222266 PMCID: PMC8248529 DOI: 10.3389/fevo.2018.00141] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
In many socially monogamous species, individuals form long-term pair bonds and males mate guard females. Such behavior is thought to help secure intra-pair fertilizations, the result of intra-pair copulations (IPCs), and ensure paternity. However, socially monogamous males are also often opportunistic and seek additional mating opportunities with other females, leaving their partner unguarded. The success associated with a male’s decision to seek more mates over guarding his partner might be impacted by the activity of other males, specifically the proportion of other males leaving their territories to seek extra-pair copulations (EPCs). The amount of EPC-seeking males can impact the likelihood of a given male encountering an unguarded paired female, but also of being cuckolded (losing IPCs). It remains unclear under which conditions it is optimal to stay and guard or seek EPCs. Using field data from socially monogamous prairie voles (Microtus ochrogaster) to generate parameters, we used optimal performance modeling (Monte Carlo simulations) to ask when is it most reproductively advantageous for a bonded male to seek EPCs, despite the risk of losing IPCs. We defined three types of males: exclusive mating bonded males (true residents), non-exclusive mating bonded residents (roving residents), and unpaired males (wanderers). We first modeled the success of an individual male living in a context that incorporated only true and roving residents. We next added wandering males to this model. Finally, we considered the effects of including wandering males and unpaired females in our model. For all contexts, we found that as EPC-seeking in the population increases, the potential reproductive benefit for seeking EPCs increasingly outpaces the rate of cuckolding. In other words, we observe a shift in optimal strategy from true residents to rovers among paired males. Our models also demonstrate that reproductive fitness is likely to remain constant, despite the shift toward obtaining success via EPCs over IPCs. Our results show the dynamic nature of reproductive decision-making, and demonstrate that alternative reproductive decisions yield subtle but important differences despite appearing as balanced strategies.
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Affiliation(s)
- Marissa A Rice
- Department of Psychology, Cornell University, Ithaca, NY, United States
| | - Luis F Restrepo
- Department of Psychology, Cornell University, Ithaca, NY, United States
| | - Alexander G Ophir
- Department of Psychology, Cornell University, Ithaca, NY, United States
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10
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Fowler-Finn KD, Boyer SL, Ikagawa R, Jeffries T, Kahn PC, Larsen EM, Lee D, Smeester M. Variation in Mating Dynamics across Five Species of Leiobunine Harvestmen (Arachnida: Opliones). BIOLOGY 2018; 7:E36. [PMID: 29904015 PMCID: PMC6022863 DOI: 10.3390/biology7020036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 05/25/2018] [Accepted: 06/09/2018] [Indexed: 11/18/2022]
Abstract
The study of mating choices often focuses on correlates of traits to the overall outcome of a mating interaction. However, mating interactions can proceed through a series of stages, with opportunities for assessment at each stage. We compared whether male or female size predicted mating interaction outcome across several stages of mating in five species of North American leiobunine harvestmen (commonly known as daddy longlegs). Leiobunine harvestmen have been previously shown to exhibit incredible morphological diversity consistent with a spectrum of male⁻female antagonism. Across all of the species, we found a general progression of female size predicting the outcome (success and timing) of early stages of interactions, and male size or male size relative to female size predicting the outcome and timing of later stages of interactions. We also found that size was not a strong predictor of outcome in the two species on the lower end of the antagonism spectrum. The variation in how female and male size predicted outcomes across species and stages of mating suggests that multiple mechanisms may operate to shape mating dynamics within and across species. Given the close relatedness of the species studied, the patterns we uncovered suggest a rapid evolution of the traits and processes predicting the outcome of mating interactions.
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Affiliation(s)
| | - Sarah L Boyer
- Biology Department, Macalester College, Saint Paul, MN 55105, USA.
| | - Raine Ikagawa
- Biology Department, Macalester College, Saint Paul, MN 55105, USA.
| | - Timothy Jeffries
- Department of Biology, Saint Louis University, Saint Louis, MO 63103, USA.
| | - Penelope C Kahn
- Biology Department, Macalester College, Saint Paul, MN 55105, USA.
| | - Eva M Larsen
- Biology Department, Macalester College, Saint Paul, MN 55105, USA.
| | - Daniel Lee
- Department of Biology, Saint Louis University, Saint Louis, MO 63103, USA.
| | - Morgan Smeester
- Department of Biology, Saint Louis University, Saint Louis, MO 63103, USA.
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11
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Fea M, Holwell GI. Exaggerated male legs increase mating success by reducing disturbance to females in the cave wētā Pachyrhamma waitomoensis. Proc Biol Sci 2018; 285:20180401. [PMID: 29875300 PMCID: PMC6015848 DOI: 10.1098/rspb.2018.0401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 05/16/2018] [Indexed: 11/12/2022] Open
Abstract
Mate guarding is a widespread behaviour resulting from sperm competition and conflict over optimal remating rates. It is a key way in which males exhibit differential mating investment, and represents a complex interplay between mating effort, intrasexual competition, opportunity costs and sexual conflict. Nevertheless, although there are many examples of exaggerated male structures used to fight rivals, few animals have developed specialized male morphological adaptations for directly sheltering females from disturbance by non-rivals. Here we report on the use of sexually dimorphic, elongated male hind legs, which are used to guard females in the New Zealand cave wētā Pachyrhamma waitomoensis (Orthoptera: Rhaphidophoridae). We found that male hind legs alongside the female failed to deter rivals from accessing her or disrupting copulation. However, they did reduce the disturbance to females from other, non-rival animals such as juveniles and heterospecifics. Males with longer hind legs were more effective in reducing disturbance, and remained with females for longer. Longer guarding periods also led to higher numbers of matings between pairs. Models of males with artificially altered hind leg dimensions also showed a benefit to greater leg length, and artificially altering the disturbance rate to females also had a significant effect on pair duration. Our results indicate that nuisance disturbance to females may play an important role in driving sexual selection on male leg length and its exaggeration in this species.
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Affiliation(s)
- Murray Fea
- School of Biological Sciences, The University of Auckland, Auckland, New Zealand
| | - Gregory I Holwell
- School of Biological Sciences, The University of Auckland, Auckland, New Zealand
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12
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Schacht R, Kramer KL, Székely T, Kappeler PM. Adult sex ratios and reproductive strategies: a critical re-examination of sex differences in human and animal societies. Philos Trans R Soc Lond B Biol Sci 2018; 372:rstb.2016.0309. [PMID: 28760753 DOI: 10.1098/rstb.2016.0309] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/12/2017] [Indexed: 11/12/2022] Open
Abstract
It is increasingly recognized that the relative proportion of potential mates to competitors in a population impacts a range of sex-specific behaviours and in particular mating and reproduction. However, while the adult sex ratio (ASR) has long been recognized as an important link between demography and behaviour, this relationship remains understudied. Here, we introduce the first inter-disciplinary collection of research on the causes and consequences of variation in the ASR in human and animal societies. This important topic is relevant to a wide audience of both social and biological scientists due to the central role that the relative number of males to females in a population plays for the evolution of, and contemporary variation in, sex roles across groups, species and higher taxa. The articles in this theme issue cover research on ASR across a variety of taxa and topics. They offer critical re-evaluations of theoretical foundations within both evolutionary and non-evolutionary fields, and propose innovative methodological approaches, present new empirical examples of behavioural consequences of ASR variation and reveal that the ASR plays a major role in determining population viability, especially in small populations and species with labile sex determination. This introductory paper puts the contributions of the theme issue into a broader context, identifies general trends across the literature and formulates directions for future research.This article is part of the themed issue 'Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'.
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Affiliation(s)
- Ryan Schacht
- Department of Anthropology, University of Utah, 270 E 1400, Salt Lake City, UT 84112, USA
| | - Karen L Kramer
- Department of Anthropology, University of Utah, 270 E 1400, Salt Lake City, UT 84112, USA
| | - Tamás Székely
- Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK.,Wissenschaftskolleg zu Berlin, Wallotstrasse 19, 14193 Berlin, Germany
| | - Peter M Kappeler
- Wissenschaftskolleg zu Berlin, Wallotstrasse 19, 14193 Berlin, Germany.,Behavioral Ecology and Sociobiology Unit, German Primate Center, Kellnerweg 4, 37077 Göttingen, Germany
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13
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Gomes BV, Guimarães DM, Szczupak D, Neves K. Female dispersion and sex ratios interact in the evolution of mating behavior: a computational model. Sci Rep 2018; 8:2467. [PMID: 29410464 PMCID: PMC5802766 DOI: 10.1038/s41598-018-20790-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 01/24/2018] [Indexed: 12/27/2022] Open
Abstract
The evolution of mating strategies is not well understood. Several hypotheses have been proposed to explain the variation in mating strategies, with varying levels of support. Specifically, female dispersion, adult sex ratio and mate guarding have been proposed as drivers of the evolution of monogamous strategies. In this study, we used an agent-based model (ABM) to examine how different mating behaviors evolve in a population under different conditions related to these putative drivers, looking to understand the interaction between them. We found an interaction among different factors in the evolution of social monogamy, and their impact is in this order: adult sex ratio (ASR), female dispersion and extra-pair copulation. Thus, when the adult sex ratio is male-biased, monogamous strategies are strongly favored. However, this is only the case if mate guarding is fully efficient, i.e., if there is no extra-pair copulation. On the other hand, in scenarios where the population is female-biased, or mate guarding is not efficient, we find that polygamous strategies are favored but proportionally to the dispersion of females. These results confirm previous findings regarding mate guarding and sex ratios, while also showing how female dispersion enters the dynamics.
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Affiliation(s)
- B V Gomes
- Morphological Sciences Graduate Program, Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - D M Guimarães
- Morphological Sciences Graduate Program, Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
| | - D Szczupak
- Morphological Sciences Graduate Program, Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - K Neves
- Morphological Sciences Graduate Program, Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
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14
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Dowling J, Webster MS. Working with what you've got: unattractive males show greater mate-guarding effort in a duetting songbird. Biol Lett 2017; 13:rsbl.2016.0682. [PMID: 28077685 DOI: 10.1098/rsbl.2016.0682] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 12/09/2016] [Indexed: 11/12/2022] Open
Abstract
When mates are limited, individuals should allocate resources to mating tactics that maximize fitness. In species with extra-pair paternity (EPP), males can invest in mate guarding, or, alternatively, in seeking EPP. Males should optimize fitness by adjusting investment according to their attractiveness to females, such that attractive males seek EPP, and unattractive males guard mates. This theory has received little empirical testing, leaving our understanding of the evolution of mating tactics incomplete; it is unclear how a male's relative attractiveness influences his tactics. We conducted observations and experiments on red-backed fairy-wrens (Malurus melanocephalus) to address this question. We found that older, more attractive (red-black) males sought EPP, whereas unattractive (brown) males invested in alternative tactics-physical and acoustic mate guarding. Younger red-black males used intermediate tactics. This suggests that males adopt mating tactics appropriate to their attributes. Males obtained similar reproductive success, suggesting these alternative tactics may maximize each male's paternity gain. Though it is likely that female choice also determines paternity, rather than just male tactics, we establish that the many interconnected components of a male's sexual phenotype influence the evolution of his decision-making rules, deepening our understanding of how mating tactics evolve under sexual selection.
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Affiliation(s)
- Jenélle Dowling
- Cornell Lab of Ornithology, Cornell University, 159 Sapsucker Woods Road, Ithaca, NY 14850, USA
| | - Michael S Webster
- Cornell Lab of Ornithology, Cornell University, 159 Sapsucker Woods Road, Ithaca, NY 14850, USA
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15
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Correlated evolution of sexually selected traits: interspecific variation in ejaculates, sperm morphology, copulatory mate guarding, and body size in two sympatric species of garter snakes. Behav Ecol Sociobiol 2017. [DOI: 10.1007/s00265-017-2414-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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16
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Kappeler PM. Sex roles and adult sex ratios: insights from mammalian biology and consequences for primate behaviour. Philos Trans R Soc Lond B Biol Sci 2017; 372:20160321. [PMID: 28760762 PMCID: PMC5540861 DOI: 10.1098/rstb.2016.0321] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/14/2017] [Indexed: 12/23/2022] Open
Abstract
Theoretical models and empirical studies in various taxa have identified important links between variation in sex roles and the number of adult males and females (adult sex ratio (ASR)) in a population. In this review, I examine these relationships in non-human primates. Because most existing theoretical models of the evolution of sex roles focus on the evolutionary origins of sex-biased behaviour, they offer only a general scaffold for predicting variation in sex roles among and within species. I argue that studies examining sex role variation at these more specific levels need to take social organization into account to identify meaningful levels for the measurement of ASR and to account for the fact that ASR and sex roles mutually influence each other. Moreover, taxon-specific life-history traits can constrain sex role flexibility and impact the operational sex ratio (OSR) by specifying the minimum length of female time outs from reproduction. Using examples from the primate literature, I highlight practical problems in estimating ASR and OSR. I then argue that interspecific variation in the occurrence of indirect forms of paternal care might indeed be linked to variation in ASR. Some studies also indicate that female aggression and bonding, as well as components of inter-sexual relationships, are sensitive to variation in ASR. Thus, links between primate sex roles and sex ratios merit further study, and such studies could prompt the development of more specific theoretical models that make realistic assumptions about taxon-specific life history and social organization.This article is part of the themed issue 'Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'.
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Affiliation(s)
- Peter M Kappeler
- Wissenschaftskolleg zu Berlin, Wallotstrasse 19, 14193 Berlin, Germany
- Behavioral Ecology and Sociobiology Unit, German Primate Center, Kellnerweg 4, 37077 Göttingen, Germany
- Department of Sociobiology/Anthropology, University of Göttingen, Kellnerweg 6, 37077 Göttingen, Germany
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The evolution of monogamy in response to partner scarcity. Sci Rep 2016; 6:32472. [PMID: 27600189 PMCID: PMC5013280 DOI: 10.1038/srep32472] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 07/26/2016] [Indexed: 11/29/2022] Open
Abstract
The evolution of monogamy and paternal care in humans is often argued to have resulted from the needs of our expensive offspring. Recent research challenges this claim, however, contending that promiscuous male competitors and the risk of cuckoldry limit the scope for the evolution of male investment. So how did monogamy first evolve? Links between mating strategies and partner availability may offer resolution. While studies of sex roles commonly assume that optimal mating rates for males are higher, fitness payoffs to monogamy and the maintenance of a single partner can be greater when partners are rare. Thus, partner availability is increasingly recognized as a key variable structuring mating behavior. To apply these recent insights to human evolution, we model three male strategies – multiple mating, mate guarding and paternal care – in response to partner availability. Under assumed ancestral human conditions, we find that male mate guarding, rather than paternal care, drives the evolution of monogamy, as it secures a partner and ensures paternity certainty in the face of more promiscuous competitors. Accordingly, we argue that while paternal investment may be common across human societies, current patterns should not be confused with the reason pairing first evolved.
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Sutter A, Lindholm AK. Meiotic drive changes sperm precedence patterns in house mice: potential for male alternative mating tactics? BMC Evol Biol 2016; 16:133. [PMID: 27328665 PMCID: PMC4915163 DOI: 10.1186/s12862-016-0710-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 06/13/2016] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND With female multiple mating (polyandry), male-male competition extends to after copulation (sperm competition). Males respond to this selective pressure through physiological, morphological and behavioural adaptations. Sperm competitiveness is commonly decreased in heterozygote carriers of male meiotic drivers, selfish genetic elements that manipulate the production of gametes in males. This might give carriers an evolutionary incentive to reduce the risk of sperm competition. Here, we explore this possibility in house mice. Natural populations frequently harbour a well-characterised male driver (t haplotype), which is transmitted to 90 % of heterozygous (+/t) males' offspring. Previous research demonstrated strong detrimental effects on sperm competitiveness, and suggested that +/t males are particularly disadvantaged against wild type males when first-to-mate. Low paternity success in the first-to-mate role is expected to favour male adaptations that decrease the risk of sperm competition by preventing female remating. Genotype-specific paternity patterns (sperm precedence) could lead to genetically determined alternative reproductive tactics that can spread through gene level selection. Here, we seek confirmation that +/t males are generally disadvantaged when first-to-mate and address whether males of different genotypes differ in reproductive tactics (copulatory and morphological) to maximise individual or driver fitness. Finally, we attempt to explain the mechanistic basis for alternative sperm precedence patterns in this species. RESULTS We confirmed that +/t males are weak sperm competitors when first to mate. When two +/t males competed, the second-to-mate was more successful, which contrasts with first male sperm precedence when wild type males competed. However, we found no differences between male genotypes in reproductive behaviour or morphology that were consistent with alternative reproductive tactics. Sperm of +/+ and +/t males differed with respect to in vitro sperm features. Premature hypermotility in +/t males' sperm can potentially explain why +/t males are very weak sperm competitors when first-to-mate. CONCLUSIONS Our results demonstrate that meiotic drivers can have strong effects on sperm precedence patterns, and may provide a heritable basis for alternative reproductive tactics motivated by reduced sperm competitiveness. We discuss how experimental and evolutionary constraints may help explain why male genotypes did not show the predicted differences.
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Affiliation(s)
- Andreas Sutter
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
| | - Anna K Lindholm
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
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Abstract
The evolution of distinctively human life history and social organization is generally attributed to paternal provisioning based on pair bonds. Here we develop an alternative argument that connects the evolution of human pair bonds to the male-biased mating sex ratios that accompanied the evolution of human life history. We simulate an agent-based model of the grandmother hypothesis, compare simulated sex ratios to data on great apes and human hunter-gatherers, and note associations between a preponderance of males and mate guarding across taxa. Then we explore a recent model that highlights the importance of mating sex ratios for differences between birds and mammals and conclude that lessons for human evolution cannot ignore mammalian reproductive constraints. In contradiction to our claim that male-biased sex ratios are characteristically human, female-biased ratios are reported in some populations. We consider the likelihood that fertile men are undercounted and conclude that the mate-guarding hypothesis for human pair bonds gains strength from explicit links with our grandmothering life history.
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