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Fresneau N, Pipoly I, Gigler D, Kosztolányi A, Székely T, Liker A. The evolution of sex roles: The importance of ecology and social environment. Proc Natl Acad Sci U S A 2024; 121:e2321294121. [PMID: 38771872 PMCID: PMC11145285 DOI: 10.1073/pnas.2321294121] [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: 12/04/2023] [Accepted: 03/27/2024] [Indexed: 05/23/2024] Open
Abstract
Males and females often have different roles in reproduction, although the origin of these differences has remained controversial. Explaining the enigmatic reversed sex roles where males sacrifice their mating potential and provide full parental care is a particularly long-standing challenge in evolutionary biology. While most studies focused on ecological factors as the drivers of sex roles, recent research highlights the significance of social factors such as the adult sex ratio. To disentangle these propositions, here, we investigate the additive and interactive effects of several ecological and social factors on sex role variation using shorebirds (sandpipers, plovers, and allies) as model organisms that provide the full spectrum of sex role variation including some of the best-known examples of sex-role reversal. Our results consistently show that social factors play a prominent role in driving sex roles. Importantly, we show that reversed sex roles are associated with both male-skewed adult sex ratios and high breeding densities. Furthermore, phylogenetic path analyses provide general support for sex ratios driving sex role variations rather than being a consequence of sex roles. Together, these important results open future research directions by showing that different mating opportunities of males and females play a major role in generating the evolutionary diversity of sex roles, mating system, and parental care.
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Affiliation(s)
- Nolwenn Fresneau
- Evolutionary Ecology Research Group, Hungarian Research Network-University of Pannonia, Veszprém8200, Hungary
- Behavioural Ecology Research Group, Center for Natural Sciences, University of Pannonia, Veszprém8200, Hungary
| | - Ivett Pipoly
- Evolutionary Ecology Research Group, Hungarian Research Network-University of Pannonia, Veszprém8200, Hungary
- Behavioural Ecology Research Group, Center for Natural Sciences, University of Pannonia, Veszprém8200, Hungary
| | - Dóra Gigler
- World Wide Fund (WWF) for Nature Hungary Foundation, Budapest1141, Hungary
| | - András Kosztolányi
- Department of Zoology, University of Veterinary Medicine, Budapest1077, Hungary
| | - Tamás Székely
- Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, Claverton Down, BathBA2 7AZ, United Kingdom
- Reproductive Strategies Research Group, Department of Evolutionary Zoology, Hungarian Research Network - University of Debrecen, Debrecen4032, Hungary
- Debrecen Biodiversity Centre, University of Debrecen, Debrecen4032, Hungary
| | - András Liker
- Evolutionary Ecology Research Group, Hungarian Research Network-University of Pannonia, Veszprém8200, Hungary
- Behavioural Ecology Research Group, Center for Natural Sciences, University of Pannonia, Veszprém8200, Hungary
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2
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Brumm H, de Framond L, Goymann W. Territorial behaviour of thrush nightingales outside the breeding season. Proc Biol Sci 2023; 290:20230496. [PMID: 37644837 PMCID: PMC10465977 DOI: 10.1098/rspb.2023.0496] [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: 03/01/2023] [Accepted: 08/04/2023] [Indexed: 08/31/2023] Open
Abstract
Territoriality is a common pattern of space use in animals that has fundamental consequences for ecological processes. In the tropics, all-year resident songbirds usually hold territories throughout the year, whereas most all-year resident temperate species are territorial only during the breeding season. In long-distance migrants, however, the situation is mostly unexplored. Here, we report findings from a Palaearctic-African migrant, the thrush nightingale Luscinia luscina. We found that only a fraction of the males was territorial in their East African winter quarters and that this was related to the stage of their song development. Individuals with full song were territorial towards other full songsters, but not towards birds that sang plastic song (i.e. an earlier stage of song development). Plastic singers were not territorial towards full songsters and often settled closely to territorial males. We suggest that territoriality of thrush nightingales in the winter quarters may be a by-product of rising testosterone levels that trigger song crystallization. Collectively, our study indicates that changes in territoriality can occur rapidly, giving rise to shifting proportions of territorial and non-territorial individuals in a population, which may lead to complex dynamics in settlement patterns and resulting ecological interactions.
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Affiliation(s)
- Henrik Brumm
- Communication and Social Behaviour Group, Max Planck Institute for Ornithology, 82319 Seewiesen, Germany
| | - Léna de Framond
- Communication and Social Behaviour Group, Max Planck Institute for Ornithology, 82319 Seewiesen, Germany
| | - Wolfgang Goymann
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, 82319 Seewiesen, Germany
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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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Fresneau N, Lee YF, Lee WC, Kosztolányi A, Székely T, Liker A. Sex Role Reversal and High Frequency of Social Polyandry in the Pheasant-Tailed Jacana (Hydrophasianus chirurgus). Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.742588] [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
In a few species, males invest more than females in parental care while the females invest in mating competition and producing multiple broods for several mates. Species in the family Jacanidae are commonly used for studying this type of breeding system (called sex-role reversal), and previous studies found discrepancies and variation between species in the expected characteristics of reversed sex roles. Yet, a better understanding of sex role differences in breeding behavior in such species is crucial for disentangling possible evolutionary mechanisms leading to this peculiar breeding system. Sex-role reversal in the pheasant-tailed jacana Hydrophasianus chirurgus has been documented long time ago. Since the very early observation of this species, however, there was no attempt to provide a comprehensive and quantitative description of their breeding. This study aims to fill these knowledge gaps by investigating the sex role differences in the breeding behavior of pheasant-tailed jacanas, by observing and monitoring a breeding population in Taiwan. We focused on three main characteristics of sex-role reversal: (1) competition between females for access to males, such as agonistic and courtship behaviors, (2) polyandrous mating, and (3) male-only care. As expected, we found that females provide most of the territory defense toward conspecifics. Males also participated in agonistic behaviors, although less frequently than females. Furthermore, contrary to what was expected, we found that males spent more time than females on courtship behavior. Polyandrous females performed mating and laying sequentially with different mates but maintained the pair bonds simultaneously with multiple males. For the first time for the species, we could estimate that the average number of mates per female (i.e., degree of polyandry) was 2.4 and that at least 81.8% of the females in the population were polyandrous. Finally, our observations corroborated that brood care is predominantly provided by males, nevertheless females were also participating to some degree in brood attendance but never in direct care (i.e., brooding). This study highlights that some aspects of polyandrous breeding might deviate from stereotyped view on sex-role reversal, and stress the importance of further within species and comparative studies in order to fully understand the mechanisms leading to sex-role reversal.
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McClelland SC, Reynolds M, Cordall M, Hauber ME, Goymann W, McClean LA, Hamama S, Lund J, Dixit T, Louder MIM, Safari I, Honza M, Spottiswoode CN, Portugal SJ. Embryo movement is more frequent in avian brood parasites than birds with parental reproductive strategies. Proc Biol Sci 2021; 288:20211137. [PMID: 34702076 PMCID: PMC8548802 DOI: 10.1098/rspb.2021.1137] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 10/04/2021] [Indexed: 12/24/2022] Open
Abstract
Movement of the embryo is essential for musculoskeletal development in vertebrates, yet little is known about whether, and why, species vary. Avian brood parasites exhibit feats of strength in early life as adaptations to exploit the hosts that rear them. We hypothesized that an increase in embryonic movement could allow brood parasites to develop the required musculature for these demands. We measured embryo movement across incubation for multiple brood-parasitic and non-parasitic bird species. Using a phylogenetically controlled analysis, we found that brood parasites exhibited significantly increased muscular movement during incubation compared to non-parasites. This suggests that increased embryo movement may facilitate the development of the stronger musculoskeletal system required for the demanding tasks undertaken by young brood parasites.
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Affiliation(s)
- Stephanie C. McClelland
- Department of Biological Sciences, School of Life and Environmental Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK
| | - Miranda Reynolds
- Department of Biological Sciences, School of Life and Environmental Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK
| | - Molly Cordall
- Department of Biological Sciences, School of Life and Environmental Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK
| | - Mark E. Hauber
- Department of Evolution, Ecology, and Behavior, School of Integrative Biology, University of Illinois, Urbana-Champaign, IL 61801, USA
- American Museum of Natural History, New York, NY 10024, USA
| | - Wolfgang Goymann
- Max-Planck-Institut für Ornithologie, Abteilung für Verhaltensneurobiologie, Eberhard-Gwinner-Str. 6a, D-82319 Seewiesen, Germany
- Coucal Project, PO Box 26, Chimala, Tanzania
| | - Luke A. McClean
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, Cape Town, South Africa
| | - Silky Hamama
- c/o Musumanene Farm, PO Box 630038, Choma, Zambia
| | - Jess Lund
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, Cape Town, South Africa
| | - Tanmay Dixit
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
| | - Matthew I. M. Louder
- Department of Evolution, Ecology, and Behavior, School of Integrative Biology, University of Illinois, Urbana-Champaign, IL 61801, USA
| | - Ignas Safari
- Max-Planck-Institut für Ornithologie, Abteilung für Verhaltensneurobiologie, Eberhard-Gwinner-Str. 6a, D-82319 Seewiesen, Germany
- Coucal Project, PO Box 26, Chimala, Tanzania
- Department of Biology, University of Dodoma, PO Box 338, Dodoma, Tanzania
| | - Marcel Honza
- The Czech Academy of Sciences, Institute of Vertebrate Biology, Květná 8, 603 65 Brno, Czech Republic
| | - Claire N. Spottiswoode
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
- FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, Cape Town, South Africa
| | - Steven J. Portugal
- Department of Biological Sciences, School of Life and Environmental Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK
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Males and females of a polygamous songbird respond differently to mating opportunities. Behav Ecol Sociobiol 2021. [DOI: 10.1007/s00265-021-03000-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Safari I, Goymann W. The evolution of reversed sex roles and classical polyandry: Insights from coucals and other animals. Ethology 2020. [DOI: 10.1111/eth.13095] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Ignas Safari
- Max‐Planck‐Institut für Ornithologie, Abteilung für Verhaltensneurobiologie Seewiesen Germany
- Coucal Project Chimala Tanzania
- Department of Biology University of Dodoma Dodoma Tanzania
| | - Wolfgang Goymann
- Max‐Planck‐Institut für Ornithologie, Abteilung für Verhaltensneurobiologie Seewiesen Germany
- Coucal Project Chimala Tanzania
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Safari I, Goymann W, Kokko H. Male-only care and cuckoldry in black coucals: does parenting hamper sex life? Proc Biol Sci 2020; 286:20182789. [PMID: 30966989 DOI: 10.1098/rspb.2018.2789] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Providing parental care often reduces additional mating opportunities. Paternal care becomes easier to understand if trade-offs between mating and caring remain mild. The black coucal Centropus grillii combines male-only parental care with 50% of all broods containing young sired by another male. To understand how much caring for offspring reduces a male's chance to sire additional young in other males' nests, we matched the production of extra-pair young in each nest with the periods during which potential extra-pair sires were either caring for offspring themselves or when they had no own offspring to care for. We found that males which cared for a clutch were not fully excluded from the pool of competitors for siring young in other males' nests. Instead, the relative siring success showed a temporary dip. Males were approximately 17% less likely to sire young in other males' nests while they were incubating, about 48% less likely to do so while feeding nestlings, followed by 26% when feeding fledglings, compared to the success of males that currently did not care for offspring. These results suggest that real-life care situations by males may involve trade-off structures that differ from, and are less strict than those frequently employed in theoretical considerations of operational sex ratios, sex roles and parenting decisions.
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Affiliation(s)
- Ignas Safari
- 1 Max-Planck-Institut für Ornithologie, Abteilung für Verhaltensneurobiologie , Eberhard-Gwinner-Straße 6a, 82319 Seewiesen , Germany.,2 Coucal Project , PO Box 26, Chimala , Tanzania.,3 Department of Conservation Biology, University of Dodoma , PO Box 338, Dodoma , Tanzania
| | - Wolfgang Goymann
- 1 Max-Planck-Institut für Ornithologie, Abteilung für Verhaltensneurobiologie , Eberhard-Gwinner-Straße 6a, 82319 Seewiesen , Germany.,2 Coucal Project , PO Box 26, Chimala , Tanzania
| | - Hanna Kokko
- 4 Department of Evolutionary Biology and Environmental Studies, University of Zurich , Zurich , Switzerland
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Lasala JA, Hughes C, Wyneken J. Female loggerhead sea turtles ( Caretta caretta L.) rarely remate during nesting season. Ecol Evol 2020; 10:163-174. [PMID: 31988720 PMCID: PMC6972835 DOI: 10.1002/ece3.5869] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 08/19/2019] [Indexed: 11/05/2022] Open
Abstract
The goal of this study was to assess the consequences of single versus multiple paternity by identifying paternity of clutches per female to identify whether there were detectable costs or benefits. Multiple mating can occur when the benefits of mating outweigh the costs, but if costs and benefits are equal, no pattern is expected. Previous research on loggerhead sea turtle (Caretta caretta) populations found male-biased breeding sex ratios and multiple mating by many females nesting in southwestern Florida. A sample of nesting loggerhead females who laid more than one nest over the course of the season and a subset of their hatchlings were examined from 36 clutches in 2016 on Sanibel Island, Florida. Males that fathered hatchlings in the first clutch sampled were identified in subsequent clutches. Interestingly, 75% of the females analyzed had mated singly. No male was represented in more than one female's clutches. The results suggest that females likely mate at the beginning of the season and use stored sperm for multiple clutches. Evidence for mating between laying events was limited. There was no consistent pattern across the subsequent multiple paternity clutches, suggesting benefits to loggerhead females likely equal their costs and subsequent mating is likely determined by female preference.
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Affiliation(s)
- Jacob A. Lasala
- Florida Atlantic UniversityBoca RatonFLUSA
- Mote Marine LaboratorySarasotaFLUSA
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Goymann W. Males paving the road to polyandry? Parental compensation in a monogamous nesting cuckoo and a classical polyandrous relative. Ethology 2019. [DOI: 10.1111/eth.12988] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Wolfgang Goymann
- Max‐Planck‐Institut für Ornithologie Abteilung für Verhaltensneurobiologie Seewiesen Germany
- Coucal Project Mbeya Tanzania
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12
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Safari I, Goymann W. Certainty of paternity in two coucal species with divergent sex roles: the devil takes the hindmost. BMC Evol Biol 2018; 18:110. [PMID: 30005606 PMCID: PMC6043945 DOI: 10.1186/s12862-018-1225-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 06/29/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Certainty of paternity is considered an important factor in the evolution of paternal care. Several meta-analyses across birds support this idea, particularly for species with altricial young. However, the role of certainty of paternity in the evolution and maintenance of exclusive paternal care in the black coucal (Centropus grillii), which is the only known altricial bird species with male-only care, is not well understood. Here we investigated whether the differences in levels of paternal care in the black coucal and its sympatric congener, the bi-parental white-browed coucal (Centropus superciliosus), are shaped by extra-pair paternity. RESULTS We found that male black coucals experienced a substantially higher loss of paternity than white-browed coucals. Further, unlike any previously reported bird species, extra-pair offspring in black coucals represented mainly the last hatchlings of the broods, and these last hatchlings were more likely to disappear during partial-brood loss. CONCLUSION The results suggest that exclusive paternal care in black coucals is not maintained by male certainty of parentage, and extra-pair fertilizations are unlikely to be a female strategy for seeking 'good genes'. Extra-pair paternity in black coucals may reflect the inability of males to guard and copulate with the female after the onset of incubation, and a female strategy to demonstrate her commitment to other males of her social group.
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Affiliation(s)
- Ignas Safari
- Max-Planck-Institut für Ornithologie, Abteilung für Verhaltensneurobiologie, Eberhard-Gwinner-Straße 6a, 82319, Seewiesen, Germany. .,Coucal Project, P.O. Box 26, Chimala, Tanzania. .,Department of Conservation Biology, University of Dodoma, P.O. Box 338, Dodoma, Tanzania.
| | - Wolfgang Goymann
- Max-Planck-Institut für Ornithologie, Abteilung für Verhaltensneurobiologie, Eberhard-Gwinner-Straße 6a, 82319, Seewiesen, Germany.,Coucal Project, P.O. Box 26, Chimala, Tanzania
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Goymann W, Trappschuh M, Urasa F. Corticosterone Concentrations Reflect Parental Expenditure in Contrasting Mating Systems of Two Coucal Species. Front Ecol Evol 2017. [DOI: 10.3389/fevo.2017.00015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Goymann W, Safari I, Muck C, Schwabl I. Sex roles, parental care and offspring growth in two contrasting coucal species. ROYAL SOCIETY OPEN SCIENCE 2016; 3:160463. [PMID: 27853561 PMCID: PMC5098986 DOI: 10.1098/rsos.160463] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 09/06/2016] [Indexed: 06/06/2023]
Abstract
The decision to provide parental care is often associated with trade-offs, because resources allocated to parental care typically cannot be invested in self-maintenance or mating. In most animals, females provide more parental care than males, but the reason for this pattern is still debated in evolutionary ecology. To better understand sex differences in parental care and its consequences, we need to study closely related species where the sexes differ in offspring care. We investigated parental care in relation to offspring growth in two closely related coucal species that fundamentally differ in sex roles and parental care, but live in the same food-rich habitat with a benign climate and have a similar breeding phenology. Incubation patterns differed and uniparental male black coucals fed their offspring two times more often than female and male white-browed coucals combined. Also, white-browed coucals had more 'off-times' than male black coucals, during which they perched and preened. However, these differences in parental care were not reflected in offspring growth, probably because white-browed coucals fed their nestlings a larger proportion of frogs than insects. A food-rich habitat with a benign climate may be a necessary, but-perhaps unsurprisingly-is not a sufficient factor for the evolution of uniparental care. In combination with previous results (Goymann et al. 2015 J. Evol. Biol. 28, 1335-1353 (doi:10.1111/jeb.12657)), these data suggest that white-browed coucals may cooperate in parental care, because they lack opportunities to become polygamous rather than because both parents were needed to successfully raise all offspring. Our case study supports recent theory suggesting that permissive environmental conditions in combination with a particular life history may induce sexual selection in females. A positive feedback loop among sexual selection, body size and adult sex-ratio may then stabilize reversed sex roles in competition and parental care.
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Affiliation(s)
- Wolfgang Goymann
- Max-Planck-Institut für Ornithologie, Abteilung für Verhaltensneurobiologie, Eberhard-Gwinner-Strasse 6a, 82319 Seewiesen, Germany
- Coucal Project, PO Box 26, Chimala, Tanzania
| | - Ignas Safari
- Max-Planck-Institut für Ornithologie, Abteilung für Verhaltensneurobiologie, Eberhard-Gwinner-Strasse 6a, 82319 Seewiesen, Germany
- Coucal Project, PO Box 26, Chimala, Tanzania
- Department of Conservation Biology, University of Dodoma, PO Box 338, Dodoma, Tanzania
| | - Christina Muck
- Max-Planck-Institut für Ornithologie, Abteilung für Verhaltensneurobiologie, Eberhard-Gwinner-Strasse 6a, 82319 Seewiesen, Germany
| | - Ingrid Schwabl
- Max-Planck-Institut für Ornithologie, Abteilung für Verhaltensneurobiologie, Eberhard-Gwinner-Strasse 6a, 82319 Seewiesen, Germany
- Coucal Project, PO Box 26, Chimala, Tanzania
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