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Abstract
AbstractSex ratios can differ from an expected equal proportion of males and females, carrying substantial implications for our understanding of how mating systems evolve. Typically, macro-evolutionary studies have been conducted without assessing how deviations from an equal sex ratio could be explained by sex-biased mortality or dispersal. Our understanding of sex ratio evolution independent of these confounds, in addition to any putative links between skewed sex ratios and other factors (e.g. life history), therefore remains largely unexplored. Here, we conducted an exploratory study investigating differences in sex ratios across closely related species while controlling for extrinsic mortality. We also tested two factors, non-overlapping/overlapping generations and the social environment, which have both been hypothesised to affect sex ratios. Specifically, we raised 15 species of killifish, which have either overlapping or discrete generations, under both solitary and social treatments. We found substantial divergences in sex ratios across closely related species, which exhibited both male and female biases. In conjunction with a low phylogenetic signal, our results suggest that sex ratios can evolve rapidly in this group. However, we found no evidence that overlapping generations or the social environment affected sex biases, suggesting that other factors drive the rapid evolution of sex ratios in killifishes.
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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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Szász E, Garamszegi LZ, Rosivall B. What is behind the variation in mate quality dependent sex ratio adjustment? - A meta-analysis. OIKOS 2019. [DOI: 10.1111/oik.05157] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Eszter Szász
- Dept of Systematic Zoology and Ecology, Eötvös Loránd Univ; Pázmány Péter sétány 1/C HU-1117 Budapest Hungary
| | - László Zsolt Garamszegi
- Depto de Ecología Evolutiva, Estación Biológica de Donaña-CSIC; Sevilla España
- MTA-ELTE-Theoretical Biology and Evolutionary Ecology Research Group, Eötvös Loránd Univ; Budapest Hungary
| | - Balázs Rosivall
- Dept of Systematic Zoology and Ecology, Eötvös Loránd Univ; Pázmány Péter sétány 1/C HU-1117 Budapest Hungary
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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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Song Z, Liu Y, Booksmythe I, Ding C. Effects of individual-based preferences for colour-banded mates on sex allocation in zebra finches. Behav Ecol 2017. [DOI: 10.1093/beheco/arx069] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Douhard M. Offspring sex ratio in mammals and the Trivers-Willard hypothesis: In pursuit of unambiguous evidence. Bioessays 2017; 39. [DOI: 10.1002/bies.201700043] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Mathieu Douhard
- Département de Biologie; Université de Sherbrooke; Sherbrooke Québec Canada
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Song Z, Lou Y, Hu Y, Deng Q, Gao W, Zhang K. Local resource competition affects sex allocation in a bird: experimental evidence. Anim Behav 2016. [DOI: 10.1016/j.anbehav.2016.08.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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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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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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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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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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Aggressive behavior of the male parent predicts brood sex ratio in a songbird. Naturwissenschaften 2014; 101:653-60. [DOI: 10.1007/s00114-014-1204-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2014] [Revised: 06/13/2014] [Accepted: 06/19/2014] [Indexed: 01/22/2023]
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Sardell RJ, DuVal EH. Differential allocation in a lekking bird: females lay larger eggs and are more likely to have male chicks when they mate with less related males. Proc Biol Sci 2013; 281:20132386. [PMID: 24225457 DOI: 10.1098/rspb.2013.2386] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The differential allocation hypothesis predicts increased investment in offspring when females mate with high-quality males. Few studies have tested whether investment varies with mate relatedness, despite evidence that non-additive gene action influences mate and offspring genetic quality. We tested whether female lekking lance-tailed manakins (Chiroxiphia lanceolata) adjust offspring sex and egg volume in response to mate attractiveness (annual reproductive success, ARS), heterozygosity and relatedness. Across 968 offspring, the probability of being male decreased with increasing parental relatedness but not father ARS or heterozygosity. This correlation tended to diminish with increasing lay-date. Across 162 offspring, egg volume correlated negatively with parental relatedness and varied with lay-date, but was unrelated to father ARS or heterozygosity. Offspring sex and egg size were unrelated to maternal age. Comparisons of maternal half-siblings in broods with no mortality produced similar results, indicating differential allocation rather than covariation between female quality and relatedness or sex-specific inbreeding depression in survival. As males suffer greater inbreeding depression, overproducing females after mating with related males may reduce fitness costs of inbreeding in a system with no inbreeding avoidance, while biasing the sex of outbred offspring towards males may maximize fitness via increased mating success of outbred sons.
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Affiliation(s)
- Rebecca J Sardell
- Department of Biological Science, Florida State University, , 319 Stadium Drive, Tallahassee, FL 32306-4295, USA
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