1
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Douhard M, Geffroy B. Males can adjust offspring sex ratio in an adaptive fashion through different mechanisms. Bioessays 2021; 43:e2000264. [PMID: 33594712 DOI: 10.1002/bies.202000264] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 01/26/2021] [Accepted: 01/26/2021] [Indexed: 01/15/2023]
Abstract
Sex allocation research has primarily focused on offspring sex-ratio adjustment by mothers. Yet, fathers also benefit from producing more of the sex with greater fitness returns. Here, we review the state-of-the art in the study of male-driven sex allocation and, counter to the current paradigm, we propose that males can adaptively influence offspring sex ratio through a wide variety of mechanisms. This includes differential production and motility of X- versus Y-bearing sperms in mammals, variation in seminal fluid composition in haplo-diploid invertebrates, and epigenetic mechanisms in some fish and lizards exhibiting environmental sex determination. Conflicts of interest between mothers and fathers over offspring sex ratios can emerge, although many more studies are needed in this area. While many studies of sex allocation have focused on adaptive explanations with little attention to mechanisms, and vice versa, the integration of these two topics is essential for understanding male-driven sex allocation.
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Affiliation(s)
- Mathieu Douhard
- Laboratoire de Biométrie & Biologie Evolutive, Université Lyon 1, Villeurbanne, France
| | - Benjamin Geffroy
- MARBEC, Univ Montpellier, Ifremer, CNRS, IRD, Palavas-Les-Flots, France
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2
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Fox RJ, Fromhage L, Jennions MD. Sexual selection, phenotypic plasticity and female reproductive output. Philos Trans R Soc Lond B Biol Sci 2019; 374:20180184. [PMID: 30966965 PMCID: PMC6365872 DOI: 10.1098/rstb.2018.0184] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/15/2018] [Indexed: 01/17/2023] Open
Abstract
In a rapidly changing environment, does sexual selection on males elevate a population's reproductive output? If so, does phenotypic plasticity enhance or diminish any such effect? We outline two routes by which sexual selection can influence the reproductive output of a population: a genetic correlation between male sexual competitiveness and female lifetime reproductive success; and direct effects of males on females' breeding success. We then discuss how phenotypic plasticity of sexually selected male traits and/or female responses (e.g. plasticity in mate choice), as the environment changes, might influence how sexual selection affects a population's reproductive output. Two key points emerge. First, condition-dependent expression of male sexual traits makes it likely that sexual selection increases female fitness if reproductively successful males disproportionately transfer genes that are under natural selection in both sexes, such as genes for foraging efficiency. Condition-dependence is a form of phenotypic plasticity if some of the variation in net resource acquisition and assimilation is attributable to the environment rather than solely genetic in origin. Second, the optimal allocation of resources into different condition-dependent traits depends on their marginal fitness gains. As male condition improves, this can therefore increase or, though rarely highlighted, actually decrease the expression of sexually selected traits. It is therefore crucial to understand how condition determines male allocation of resources to different sexually selected traits that vary in their immediate effects on female reproductive output (e.g. ornaments versus coercive behaviour). In addition, changes in the distribution of condition among males as the environment shifts could reduce phenotypic variance in certain male traits, thereby reducing the strength of sexual selection imposed by females. Studies of adaptive evolution under rapid environmental change should consider the possibility that phenotypic plasticity of sexually selected male traits, even if it elevates male fitness, could have a negative effect on female reproductive output, thereby increasing the risk of population extinction. This article is part of the theme issue 'The role of plasticity in phenotypic adaptation to rapid environmental change'.
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Affiliation(s)
- Rebecca J. Fox
- Division of Ecology and Evolution, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Lutz Fromhage
- Department of Biological and Environmental Science, University of Jyvaskyla, PO Box 35, Jyvaskyla 40014, Finland
| | - Michael D. Jennions
- Division of Ecology and Evolution, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
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3
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Costanzo A, Rubolini D, Ambrosini R, Caprioli M, Gatti E, Romano A, Parolini M, Gianfranceschi L, Saino N. Association between extra-pair paternity and nestling sex and condition in the barn swallow. Behav Ecol Sociobiol 2018. [DOI: 10.1007/s00265-018-2552-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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4
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Affiliation(s)
- Mathieu Douhard
- Département de Biologie; Université de Sherbrooke; 2500 boulevard de l’ Université Sherbrooke QC J1K 2R1 Canada
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5
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Costanzo A, Ambrosini R, Caprioli M, Gatti E, Parolini M, Canova L, Rubolini D, Romano A, Gianfranceschi L, Saino N. Lifetime reproductive success, selection on lifespan, and multiple sexual ornaments in male European barn swallows. Evolution 2017; 71:2457-2468. [DOI: 10.1111/evo.13312] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 06/30/2017] [Indexed: 01/15/2023]
Affiliation(s)
- Alessandra Costanzo
- Department of Environmental Science and Policy; University of Milan; via Celoria 26, I-20133 Milan Italy
| | - Roberto Ambrosini
- Department of Earth and Environmental Sciences (DISAT); University of Milano Bicocca; Piazza della Scienza, 1, I-20126 Milan Italy
| | - Manuela Caprioli
- Department of Environmental Science and Policy; University of Milan; via Celoria 26, I-20133 Milan Italy
| | - Emanuele Gatti
- Department of Biosciences; University of Milan; via Celoria 26, I-20133 Milan Italy
| | - Marco Parolini
- Department of Environmental Science and Policy; University of Milan; via Celoria 26, I-20133 Milan Italy
| | - Luca Canova
- Department of Chemistry; Via Taramelli 12, I-27100 Pavia Italy
| | - Diego Rubolini
- Department of Environmental Science and Policy; University of Milan; via Celoria 26, I-20133 Milan Italy
| | - Andrea Romano
- Department of Environmental Science and Policy; University of Milan; via Celoria 26, I-20133 Milan Italy
| | - Luca Gianfranceschi
- Department of Earth and Environmental Sciences (DISAT); University of Milano Bicocca; Piazza della Scienza, 1, I-20126 Milan Italy
| | - Nicola Saino
- Department of Environmental Science and Policy; University of Milan; via Celoria 26, I-20133 Milan Italy
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6
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Veller C, Haig D, Nowak MA. The Trivers-Willard hypothesis: sex ratio or investment? Proc Biol Sci 2017; 283:rspb.2016.0126. [PMID: 27170721 DOI: 10.1098/rspb.2016.0126] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 04/18/2016] [Indexed: 11/12/2022] Open
Abstract
The Trivers-Willard hypothesis has commonly been considered to predict two things. First, that a mother in good condition should bias the sex ratio of her offspring towards males (if males exhibit greater variation in reproductive value). Second, that a mother in good condition should invest more per son than per daughter. These two predictions differ empirically, mechanistically and, as we demonstrate here, theoretically too. We construct a simple model of sex allocation that allows simultaneous analysis of both versions of the Trivers-Willard hypothesis. We show that the sex ratio version holds under very general conditions, being valid for a large class of male and female fitness functions. The investment version, on the other hand, is shown to hold only for a small subset of male and female fitness functions. Our results help to make sense of the observation that the sex ratio version is empirically more successful than the investment version.
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Affiliation(s)
- Carl Veller
- Department of Organismic and Evolutionary Biology, Harvard University, MA, USA Program for Evolutionary Dynamics, Harvard University, MA, USA
| | - David Haig
- Department of Organismic and Evolutionary Biology, Harvard University, MA, USA
| | - Martin A Nowak
- Department of Organismic and Evolutionary Biology, Harvard University, MA, USA Program for Evolutionary Dynamics, Harvard University, MA, USA Department of Mathematics, Harvard University, MA, USA
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7
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Shyu E, Caswell H. Frequency-dependent two-sex models: a new approach to sex ratio evolution with multiple maternal conditions. Ecol Evol 2016; 6:6855-6879. [PMID: 27980727 PMCID: PMC5139946 DOI: 10.1002/ece3.2202] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Revised: 05/02/2016] [Accepted: 05/04/2016] [Indexed: 11/12/2022] Open
Abstract
Mothers that experience different individual or environmental conditions may produce different proportions of male to female offspring. The Trivers-Willard hypothesis, for instance, suggests that mothers with different qualities (size, health, etc.) will use different sex ratios if maternal quality differentially affects sex-specific reproductive success. Condition-dependent, or facultative, sex ratio strategies like these allow multiple sex ratios to coexist within a population. They also create complex population structure due to the presence of multiple maternal conditions. As a result, modeling facultative sex ratio evolution requires not only sex ratio strategies with multiple components, but also two-sex population models with explicit stage structure. To this end, we combine nonlinear, frequency-dependent matrix models and multidimensional adaptive dynamics to create a new framework for studying sex ratio evolution. We illustrate the applications of this framework with two case studies where the sex ratios depend one of two possible maternal conditions (age or quality). In these cases, we identify evolutionarily singular sex ratio strategies, find instances where one maternal condition produces exclusively male or female offspring, and show that sex ratio biases depend on the relative reproductive value ratios for each sex.
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Affiliation(s)
- Esther Shyu
- Biology Department MS-34 Woods Hole Oceanographic Institution Woods Hole Massachusetts 02543
| | - Hal Caswell
- Biology Department MS-34 Woods Hole Oceanographic Institution Woods Hole Massachusetts 02543; Institute for Biodiversity and Ecosystem Dynamics University of Amsterdam Amsterdam The Netherlands
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8
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Durand G, Lessard S. Fixation probability in a two-locus intersexual selection model. Theor Popul Biol 2016; 109:75-87. [DOI: 10.1016/j.tpb.2016.03.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 03/24/2016] [Accepted: 03/28/2016] [Indexed: 10/22/2022]
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9
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Romano A, Costanzo A, Caprioli M, Parolini M, Ambrosini R, Rubolini D, Saino N. Better-surviving barn swallow mothers produce more and better-surviving sons. Evolution 2016; 70:1120-8. [PMID: 26990898 DOI: 10.1111/evo.12908] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 03/04/2016] [Accepted: 03/08/2016] [Indexed: 11/28/2022]
Abstract
Sex allocation theory predicts that parents are selected to bias their progeny sex ratio (SR) toward the sex that will benefit the most from parental quality. Because parental quality may differentially affect survival of sons and daughters, a pivotal test of the adaptive value of SR adjustment is whether parents overproduce offspring of the sex that accrues larger fitness advantages from high parental quality. However, this crucial test of the long-term fitness consequences of sex allocation decisions has seldom been performed. In this study of the barn swallow (Hirundo rustica), we showed a positive correlation between the proportion of sons and maternal annual survival. We then experimentally demonstrated that this association did not depend on the differential costs of rearing offspring of either sex. Finally, we showed that maternal lifespan positively predicted lifespan of sons but not of daughters. Because in barn swallows lifespan is a strong determinant of lifetime reproductive success, the results suggest that mothers overproduce offspring of the sex that benefits the most from maternal quality. Hence, irrespective of mechanisms causing the SR bias and mother-son covariation in lifespan, we provide strong evidence that sex allocation decisions of mothers can highly impact on their lifetime fitness.
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Affiliation(s)
- Andrea Romano
- Department of Biosciences, University of Milan, I-20133, Milan, Italy.
| | | | - Manuela Caprioli
- Department of Biosciences, University of Milan, I-20133, Milan, Italy
| | - Marco Parolini
- Department of Biosciences, University of Milan, I-20133, Milan, Italy
| | - Roberto Ambrosini
- Department of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, I-20126, Milan, Italy
| | - Diego Rubolini
- Department of Biosciences, University of Milan, I-20133, Milan, Italy
| | - Nicola Saino
- Department of Biosciences, University of Milan, I-20133, Milan, Italy.
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10
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Are there physiological constraints on maternal ability to adjust sex ratios in mammals? J Zool (1987) 2016. [DOI: 10.1111/jzo.12327] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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11
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Douhard M, Festa-Bianchet M, Coltman DW, Pelletier F. Paternal reproductive success drives sex allocation in a wild mammal. Evolution 2016; 70:358-68. [DOI: 10.1111/evo.12860] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 01/10/2016] [Indexed: 01/08/2023]
Affiliation(s)
- Mathieu Douhard
- Département de biologie and Centre d’Études Nordiques; Université de Sherbrooke; 2500 boulevard de l'Université Sherbrooke Québec J1K 2R1 Canada
| | - Marco Festa-Bianchet
- Département de biologie and Centre d’Études Nordiques; Université de Sherbrooke; 2500 boulevard de l'Université Sherbrooke Québec J1K 2R1 Canada
| | - David W. Coltman
- Department of Biological Sciences; University of Alberta; Edmonton Alberta T6G 2E9 Canada
| | - Fanie Pelletier
- Département de biologie and Centre d’Études Nordiques; Université de Sherbrooke; 2500 boulevard de l'Université Sherbrooke Québec J1K 2R1 Canada
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12
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Booksmythe I, Mautz B, Davis J, Nakagawa S, Jennions MD. Facultative adjustment of the offspring sex ratio and male attractiveness: a systematic review and meta-analysis. Biol Rev Camb Philos Soc 2015; 92:108-134. [DOI: 10.1111/brv.12220] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Revised: 08/09/2015] [Accepted: 08/28/2015] [Indexed: 01/12/2023]
Affiliation(s)
- Isobel Booksmythe
- Division of Evolution, Ecology & Genetics; Research School of Biology, The Australian National University; Daley road Canberra Australian Capital Territory 2601 Australia
- Department of Animal Ecology; Evolutionary Biology Centre, Uppsala University; Norbyvägen 18D SE-75236 Uppsala Sweden
- Institute of Evolutionary Biology and Environmental Studies; University of Zürich; Winterthurerstrasse 190 CH-8057 Zürich Switzerland
| | - Brian Mautz
- Division of Evolution, Ecology & Genetics; Research School of Biology, The Australian National University; Daley road Canberra Australian Capital Territory 2601 Australia
- Department of Animal Ecology; Evolutionary Biology Centre, Uppsala University; Norbyvägen 18D SE-75236 Uppsala Sweden
| | - Jacqueline Davis
- Division of Evolution, Ecology & Genetics; Research School of Biology, The Australian National University; Daley road Canberra Australian Capital Territory 2601 Australia
- Department of Psychology; University of Cambridge; Downing Street CB2 3EB Cambridge U.K
| | - Shinichi Nakagawa
- Department of Zoology; University of Otago; PO Box 56 Dunedin 9054 New Zealand
- Evolution & Ecology Research Centre, School of Biological, Earth and Environmental Sciences; University of New South Wales; Sydney New South Wales 2052 Australia
| | - Michael D. Jennions
- Division of Evolution, Ecology & Genetics; Research School of Biology, The Australian National University; Daley road Canberra Australian Capital Territory 2601 Australia
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13
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Calsbeek R, Duryea MC, Goedert D, Bergeron P, Cox RM. Intralocus sexual conflict, adaptive sex allocation, and the heritability of fitness. J Evol Biol 2015; 28:1975-85. [PMID: 26310599 DOI: 10.1111/jeb.12713] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2014] [Revised: 06/25/2015] [Accepted: 07/29/2015] [Indexed: 11/27/2022]
Abstract
Intralocus sexual conflict arises when selection favours alternative fitness optima in males and females. Unresolved conflict can create negative between-sex genetic correlations for fitness, such that high-fitness parents produce high-fitness progeny of their same sex, but low-fitness progeny of the opposite sex. This cost of sexual conflict could be mitigated if high-fitness parents bias sex allocation to produce more offspring of their same sex. Previous studies of the brown anole lizard (Anolis sagrei) show that viability selection on body size is sexually antagonistic, favouring large males and smaller females. However, sexual conflict over body size may be partially mitigated by adaptive sex allocation: large males sire more sons than daughters, whereas small males sire more daughters than sons. We explored the evolutionary implications of these phenomena by assessing the additive genetic (co)variance of fitness within and between sexes in a wild population. We measured two components of fitness: viability of adults over the breeding season, and the number of their progeny that survived to sexual maturity, which includes components of parental reproductive success and offspring viability (RS(V) ). Viability of parents was not correlated with adult viability of their sons or daughters. RS(V) was positively correlated between sires and their offspring, but not between dams and their offspring. Neither component of fitness was significantly heritable, and neither exhibited negative between-sex genetic correlations that would indicate unresolved sexual conflict. Rather, our results are more consistent with predictions regarding adaptive sex allocation in that, as the number of sons produced by a sire increased, the adult viability of his male progeny increased.
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Affiliation(s)
- R Calsbeek
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | - M C Duryea
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | - D Goedert
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA.,CAPES Foundation, Ministry of Education of Brazil, Brasília, DF, Brazil
| | - P Bergeron
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | - R M Cox
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
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14
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Romano A, Romano M, Caprioli M, Costanzo A, Parolini M, Rubolini D, Saino N. Sex allocation according to multiple sexually dimorphic traits of both parents in the barn swallow (Hirundo rustica). J Evol Biol 2015; 28:1234-47. [PMID: 25913917 DOI: 10.1111/jeb.12650] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 04/21/2015] [Accepted: 04/23/2015] [Indexed: 01/10/2023]
Abstract
Parents should differentially invest in sons or daughters depending on the sex-specific fitness returns from male and female offspring. In species with sexually selected heritable male characters, highly ornamented fathers should overproduce sons, which will be more sexually attractive than sons of less ornamented fathers. Because of genetic correlations between the sexes, females that express traits which are under selection in males should also overproduce sons. However, sex allocation strategies may consist in reaction norms leading to spatiotemporal variation in the association between offspring sex ratio (SR) and parental phenotype. We analysed offspring SR in barn swallows (Hirundo rustica) over 8 years in relation to two sexually dimorphic traits: tail length and melanin-based ventral plumage coloration. The proportion of sons increased with maternal plumage darkness and paternal tail length, consistently with sexual dimorphism in these traits. The size of the effect of these parental traits on SR was large compared to other studies of offspring SR in birds. Barn swallows thus manipulate offspring SR to overproduce 'sexy sons' and potentially to mitigate the costs of intralocus sexually antagonistic selection. Interannual variation in the relationships between offspring SR and parental traits was observed which may suggest phenotypic plasticity in sex allocation and provides a proximate explanation for inconsistent results of studies of sex allocation in relation to sexual ornamentation in birds.
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Affiliation(s)
- A Romano
- Department of Biosciences, University of Milan, Milan, Italy
| | - M Romano
- Department of Biosciences, University of Milan, Milan, Italy
| | - M Caprioli
- Department of Biosciences, University of Milan, Milan, Italy
| | - A Costanzo
- Department of Biosciences, University of Milan, Milan, Italy
| | - M Parolini
- Department of Biosciences, University of Milan, Milan, Italy
| | - D Rubolini
- Department of Biosciences, University of Milan, Milan, Italy
| | - N Saino
- Department of Biosciences, University of Milan, Milan, Italy
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15
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Bocedi G, Reid JM. Evolution of female multiple mating: A quantitative model of the "sexually selected sperm" hypothesis. Evolution 2014; 69:39-58. [PMID: 25330405 PMCID: PMC4312924 DOI: 10.1111/evo.12550] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 10/01/2014] [Indexed: 12/03/2022]
Abstract
Explaining the evolution and maintenance of polyandry remains a key challenge in evolutionary ecology. One appealing explanation is the sexually selected sperm (SSS) hypothesis, which proposes that polyandry evolves due to indirect selection stemming from positive genetic covariance with male fertilization efficiency, and hence with a male's success in postcopulatory competition for paternity. However, the SSS hypothesis relies on verbal analogy with “sexy-son” models explaining coevolution of female preferences for male displays, and explicit models that validate the basic SSS principle are surprisingly lacking. We developed analogous genetically explicit individual-based models describing the SSS and “sexy-son” processes. We show that the analogy between the two is only partly valid, such that the genetic correlation arising between polyandry and fertilization efficiency is generally smaller than that arising between preference and display, resulting in less reliable coevolution. Importantly, indirect selection was too weak to cause polyandry to evolve in the presence of negative direct selection. Negatively biased mutations on fertilization efficiency did not generally rescue runaway evolution of polyandry unless realized fertilization was highly skewed toward a single male, and coevolution was even weaker given random mating order effects on fertilization. Our models suggest that the SSS process is, on its own, unlikely to generally explain the evolution of polyandry.
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Affiliation(s)
- Greta Bocedi
- Institute of Biological and Environmental Sciences, University of Aberdeen, Zoology Building, Tillydrone Avenue, Aberdeen, AB24 2TZ, United Kingdom.
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16
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Tazzyman SJ, Iwasa Y, Pomiankowski A. The handicap process favors exaggerated, rather than reduced, sexual ornaments. Evolution 2014; 68:2534-49. [PMID: 24837599 PMCID: PMC4277338 DOI: 10.1111/evo.12450] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Accepted: 05/07/2014] [Indexed: 11/28/2022]
Abstract
Why are traits that function as secondary sexual ornaments generally exaggerated in size compared to the naturally selected optimum, and not reduced? Because they deviate from the naturally selected optimum, traits that are reduced in size will handicap their bearer, and could thus provide an honest signal of quality to a potential mate. Thus if secondary sexual ornaments evolve via the handicap process, current theory suggests that reduced ornamentation should be as frequent as exaggerated ornamentation, but this is not the case. To try to explain this discrepancy, we analyze a simple model of the handicap process. Our analysis shows that asymmetries in costs of preference or ornament with regard to exaggeration and reduction cannot fully explain the imbalance. Rather, the bias toward exaggeration can be best explained if either the signaling efficacy or the condition dependence of a trait increases with size. Under these circumstances, evolution always leads to more extreme exaggeration than reduction: although the two should occur just as frequently, exaggerated secondary sexual ornaments are likely to be further removed from the naturally selected optimum than reduced ornaments.
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Affiliation(s)
- Samuel J Tazzyman
- CoMPLEX, , University College London, London WC1E 6BT, United Kingdom; Institute of Integrative Biology (IBZ), ETH Zürich, Zürich 8092, Switzerland; The Galton Laboratory, , Department of Genetics, Environment, and Evolution, , University College London, London WC1E 6BT, United Kingdom.
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17
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Conflict over resources generates conflict over mate choice: reply to Smaldino and Newson. EVOL HUM BEHAV 2014. [DOI: 10.1016/j.evolhumbehav.2013.12.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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18
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Tazzyman SJ, Iwasa Y, Pomiankowski A. Signaling efficacy drives the evolution of larger sexual ornaments by sexual selection. Evolution 2014; 68:216-29. [PMID: 24099137 PMCID: PMC3920633 DOI: 10.1111/evo.12255] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 08/10/2013] [Indexed: 11/27/2022]
Abstract
Why are there so few small secondary sexual characters? Theoretical models predict that sexual selection should lead to reduction as often as exaggeration, and yet we mainly associate secondary sexual ornaments with exaggerated features such as the peacock's tail. We review the literature on mate choice experiments for evidence of reduced sexual traits. This shows that reduced ornamentation is effectively impossible in certain types of ornamental traits (behavioral, pheromonal, or color-based traits, and morphological ornaments for which the natural selection optimum is no trait), but that there are many examples of morphological traits that would permit reduction. Yet small sexual traits are very rarely seen. We analyze a simple mathematical model of Fisher's runaway process (the null model for sexual selection). Our analysis shows that the imbalance cannot be wholly explained by larger ornaments being less costly than smaller ornaments, nor by preferences for larger ornaments being less costly than preferences for smaller ornaments. Instead, we suggest that asymmetry in signaling efficacy limits runaway to trait exaggeration.
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Affiliation(s)
- Samuel J Tazzyman
- Theoretical Biology, Institute of Integrative Biology, ETH Zürich, Universitätstrasse 16, CH-8092, Zürich, Switzerland; CoMPLEX, University College London, Gower Street, London, WC1E 6BT, United Kingdom; The Galton Laboratory, Department of Genetics, Environment, and Evolution, University College London, Gower Street, London, WC1E 6BT, United Kingdom.
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19
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Featherston R, Jones TM, Elgar MA. Female resistance behaviour and progeny sex ratio in two Bradysia
species (Diptera: Sciaridae) with paternal genome elimination. J Evol Biol 2013; 26:919-28. [DOI: 10.1111/jeb.12117] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2011] [Accepted: 12/28/2012] [Indexed: 11/29/2022]
Affiliation(s)
- R. Featherston
- Department of Zoology; The University of Melbourne; Melbourne Victoria Australia
| | - T. M. Jones
- Department of Zoology; The University of Melbourne; Melbourne Victoria Australia
| | - M. A. Elgar
- Department of Zoology; The University of Melbourne; Melbourne Victoria Australia
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20
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Booksmythe I, Schwanz LE, Kokko H. THE COMPLEX INTERPLAY OF SEX ALLOCATION AND SEXUAL SELECTION. Evolution 2012; 67:673-8. [DOI: 10.1111/evo.12003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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21
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Kuijper B, Pen I, Weissing FJ. A Guide to Sexual Selection Theory. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2012. [DOI: 10.1146/annurev-ecolsys-110411-160245] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Mathematical models have played an important role in the development of sexual selection theory. These models come in different flavors and they differ in their assumptions, often in a subtle way. Similar questions can be addressed by modeling frameworks from population genetics, quantitative genetics, evolutionary game theory, or adaptive dynamics, or by individual-based simulations. Confronted with such diversity, nonspecialists may have difficulties judging the scope and limitations of the various approaches. Here we review the major modeling frameworks, highlighting their pros and cons when applied to different research questions. We also discuss recent developments, where classical models are enriched by including more detail regarding genetics, behavior, demography, and population dynamics. It turns out that some seemingly well-established conclusions of sexual selection theory are less general than previously thought. Linking sexual selection to other processes such as sex-ratio evolution or speciation also reveals that enriching the theory can lead to surprising new insights.
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Affiliation(s)
- Bram Kuijper
- Theoretical Biology Group, Center for Ecological and Evolutionary Studies, University of Groningen, 9747 AG Groningen, The Netherlands;, ,
- Behavior and Evolution Group, Department of Zoology, University of Cambridge, CB2 3EJ Cambridge, United Kingdom
| | - Ido Pen
- Theoretical Biology Group, Center for Ecological and Evolutionary Studies, University of Groningen, 9747 AG Groningen, The Netherlands;, ,
| | - Franz J. Weissing
- Theoretical Biology Group, Center for Ecological and Evolutionary Studies, University of Groningen, 9747 AG Groningen, The Netherlands;, ,
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Bowers EK, Munclinger P, Bureš S, Kučerová L, Nádvorník P, Krist M. Cross-fostering eggs reveals that female collared flycatchers adjust clutch sex ratios according to parental ability to invest in offspring. Mol Ecol 2012; 22:215-28. [PMID: 23116299 DOI: 10.1111/mec.12106] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Revised: 09/20/2012] [Accepted: 10/02/2012] [Indexed: 12/14/2022]
Abstract
Across animal taxa, reproductive success is generally more variable and more strongly dependent upon body condition for males than for females; in such cases, parents able to produce offspring in above-average condition are predicted to produce sons, whereas parents unable to produce offspring in good condition should produce daughters. We tested this hypothesis in the collared flycatcher (Ficedula albicollis) by cross-fostering eggs among nests and using the condition of foster young that parents raised to fledging as a functional measure of their ability to produce fit offspring. As predicted, females raising heavier-than-average foster fledglings with their social mate initially produced male-biased primary sex ratios, whereas those raising lighter-than-average foster fledglings produced female-biased primary sex ratios. Females also produced male-biased clutches when mated to males with large secondary sexual characters (wing patches), and tended to produce male-biased clutches earlier within breeding seasons relative to females breeding later. However, females did not adjust the sex of individuals within their clutches; sex was distributed randomly with respect to egg size, laying order and paternity. Future research investigating the proximate mechanisms linking ecological contexts and the quality of offspring parents are able to produce with primary sex-ratio variation could provide fundamental insight into the evolution of context-dependent sex-ratio adjustment.
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Affiliation(s)
- E Keith Bowers
- Behavior, Ecology, Evolution, and Systematics Section, School of Biological Sciences, Illinois State University, Normal, IL, USA
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Sex-ratio control erodes sexual selection, revealing evolutionary feedback from adaptive plasticity. Proc Natl Acad Sci U S A 2011; 108:15925-30. [PMID: 21911375 DOI: 10.1073/pnas.1105721108] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Female choice is a powerful selective force, driving the elaboration of conspicuous male ornaments. This process of sexual selection has profound implications for many life-history decisions, including sex allocation. For example, females with attractive partners should produce more sons, because these sons will inherit their father's attractiveness and enjoy high mating success, thereby yielding greater fitness returns than daughters. However, previous research has overlooked the fact that there is a reciprocal feedback from life-history strategies to sexual selection. Here, using a simple mathematical model, we show that if mothers adaptively control offspring sex in relation to their partner's attractiveness, sexual selection is weakened and male ornamentation declines. This weakening occurs because the ability to determine offspring sex reduces the fitness difference between females with attractive and unattractive partners. We use individual-based, evolutionary simulations to show that this result holds under more biologically realistic conditions. Sexual selection and sex allocation thus interact in a dynamic fashion: The evolution of conspicuous male ornaments favors sex-ratio adjustment, but this conditional strategy then undermines the very same process that generated it, eroding sexual selection. We predict that, all else being equal, the most elaborate sexual displays should be seen in species with little or no control over offspring sex. The feedback process we have described points to a more general evolutionary principle, in which a conditional strategy weakens directional selection on another trait by reducing fitness differences.
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Pryke SR, Rollins LA, Griffith SC. CONTEXT-DEPENDENT SEX ALLOCATION: CONSTRAINTS ON THE EXPRESSION AND EVOLUTION OF MATERNAL EFFECTS. Evolution 2011; 65:2792-9. [DOI: 10.1111/j.1558-5646.2011.01391.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Blackburn GS, Albert AYK, Otto SP. The evolution of sex ratio adjustment in the presence of sexually antagonistic selection. Am Nat 2010; 176:264-75. [PMID: 20653443 DOI: 10.1086/655220] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Sex ratio adjustment (SRA) of broods has received widespread interest as a means for optimizing parental investment in offspring. Classical explanations for the evolution of SRA focus on improving offspring fitness in light of resource availability or mate attractiveness. Here, we use genetic models to demonstrate that SRA can evolve to alleviate sexual antagonism by improving the chance that the alleles of a sexually antagonistic trait are transmitted to the sex they benefit. In cases where the trait is autosomally inherited, this result is obtained regardless of whether SRA is based on the mother's or the father's genotype and irrespective of the recombination rate between the trait and SRA loci. SRA also evolves in this manner when the trait is sex-linked, provided that SRA decisions are based on the homogametic genotype (XX mothers or ZZ fathers). By contrast, when based on traits in the heterogametic sex, SRA promotes fixation of the allele that is detrimental to that sex, preventing the evolution of substantial levels of SRA. Our models indicate that the evolution of SRA in nature should be strongly influenced by the genetic architecture of the traits on which it is based and the form of selection affecting them.
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Affiliation(s)
- Gwylim S Blackburn
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, Canada
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House CM, Simmons LW, Kotiaho JS, Tomkins JL, Hunt J. Sex ratio bias in the dung beetle Onthophagus taurus: adaptive allocation or sex-specific offspring mortality? Evol Ecol 2010. [DOI: 10.1007/s10682-010-9423-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Pryke SR, Griffith SC. Genetic incompatibility drives sex allocation and maternal investment in a polymorphic finch. Science 2009; 323:1605-7. [PMID: 19299618 DOI: 10.1126/science.1168928] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Genetic compatibility may drive individual mate choice decisions because of predictable fitness effects associated with breeding with incompatible partners. In Gouldian finches (Erythrura gouldiae), females paired with genetically incompatible males of alternative color morphs overproduce sons, presumably to reduce investment in inviable daughters. We also observed a reduced overall investment in clutch size, egg size, and care to offspring resulting from incompatible matings. Within-female experimental pairings demonstrate that female birds have the ability to adaptively adjust the sex of their eggs and allocate resources on the basis of partner quality. Female Gouldian finches thus make cumulative strategic allocation decisions to minimize the costs of poor-quality pairings when faced with a genetically incompatible partner.
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Affiliation(s)
- Sarah R Pryke
- Department of Brain, Behaviour, and Evolution, Macquarie University, Sydney, NSW 2109, Australia.
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Addison B, Kitaysky AS, Hipfner JM. Sex allocation in a monomorphic seabird with a single-egg clutch: test of the environment, mate quality, and female condition hypotheses. Behav Ecol Sociobiol 2008. [DOI: 10.1007/s00265-008-0643-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Cockburn A, Double MC. Cooperatively breeding superb fairy-wrens show no facultative manipulation of offspring sex ratio despite plausible benefits. Behav Ecol Sociobiol 2007. [DOI: 10.1007/s00265-007-0492-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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