1
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Cīrulis A, Nordén AK, Churcher AM, Ramm SA, Zadesenets KS, Abbott JK. Sex-limited experimental evolution drives transcriptomic divergence in a hermaphrodite. Genome Biol Evol 2024; 16:evad235. [PMID: 38155579 PMCID: PMC10786194 DOI: 10.1093/gbe/evad235] [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: 02/22/2023] [Revised: 12/12/2023] [Accepted: 12/23/2023] [Indexed: 12/30/2023] Open
Abstract
The evolution of gonochorism from hermaphroditism is linked with the formation of sex chromosomes, as well as the evolution of sex-biased and sex-specific gene expression to allow both sexes to reach their fitness optimum. There is evidence that sexual selection drives the evolution of male-biased gene expression in particular. However, previous research in this area in animals comes from either theoretical models or comparative studies of already old sex chromosomes. We therefore investigated changes in gene expression under 3 different selection regimes for the simultaneous hermaphrodite Macrostomum lignano subjected to sex-limited experimental evolution (i.e. selection for fitness via eggs, sperm, or a control regime allowing both). After 21 and 22 generations of selection for male-specific or female-specific fitness, we characterized changes in whole-organism gene expression. We found that female-selected lines had changed the most in their gene expression. Although annotation for this species is limited, gene ontology term and Kyoto Encyclopedia of Genes and Genomes pathway analyses suggest that metabolic changes (e.g. biosynthesis of amino acids and carbon metabolism) are an important adaptive component. As predicted, we found that the expression of genes previously identified as testis-biased candidates tended to be downregulated in the female-selected lines. We did not find any significant expression differences for previously identified candidates of other sex-specific organs, but this may simply reflect that few transcripts have been characterized in this way. In conclusion, our experiment suggests that changes in testis-biased gene expression are important in the early evolution of sex chromosomes and gonochorism.
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Affiliation(s)
- Aivars Cīrulis
- Department of Biology, Lund University, 223 62 Lund, Sweden
- Laboratory of Microbiology and Pathology, Institute of Food Safety, Animal Health and Environment “BIOR,”Riga LV-1076, Latvia
- Faculty of Biology, University of Latvia, Riga LV-1004, Latvia
| | - Anna K Nordén
- Department of Biology, Lund University, 223 62 Lund, Sweden
| | - Allison M Churcher
- Department of Molecular Biology, National Bioinformatics Infrastructure Sweden, Umeå University, 901 87 Umeå, Sweden
| | - Steven A Ramm
- Department of Evolutionary Biology, Bielefeld University, 33615 Bielefeld, Germany
- UMR 6553 ECOBIO, Université de Rennes, 35042 Rennes, France
| | - Kira S Zadesenets
- Department of Molecular Genetics, Cell Biology and Bionformatics, The Federal Research Center Institute of Cytology and Genetics SB RAS, 630090 Novosibirsk, Russian Federation
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2
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Janicke T, Chapuis E, Meconcelli S, Bonel N, Delahaie B, David P. Environmental effects on the genetic architecture of fitness components in a simultaneous hermaphrodite. J Anim Ecol 2021; 91:124-137. [PMID: 34652857 DOI: 10.1111/1365-2656.13607] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 10/04/2021] [Indexed: 12/01/2022]
Abstract
Understanding how environmental change affects genetic variances and covariances of reproductive traits is key to formulate firm predictions on evolutionary responses. This is particularly true for sex-specific variance in reproductive success, which has been argued to affect how populations can adapt to environmental change. Our current knowledge on the impact of environmental stress on sex-specific genetic architecture of fitness components is still limited and restricted to separate-sexed organisms. However, hermaphroditism is widespread across animals and may entail interesting peculiarities with respect to genetic constraints imposed on the evolution of male and female reproduction. We explored how food restriction affects the genetic variance-covariance (G) matrix of body size and reproductive success of the simultaneously hermaphroditic freshwater snail Physa acuta. Our results provide strong evidence that the imposed environmental stress elevated the opportunity for selection in both sex functions. However, the G-matrix remained largely stable across the tested food treatments. Importantly, our results provide no support for cross-sex genetic correlations suggesting no strong evolutionary coupling of male and female reproductive traits. We discuss potential implications for the adaptation to changing environments and highlight the need for more quantitative genetic studies on male and female fitness components in simultaneous hermaphrodites.
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Affiliation(s)
- Tim Janicke
- Centre d'Écologie Fonctionnelle et Évolutive, CNRS, Univ Montpellier, EPHE, IRD, Montpellier, France.,Applied Zoology, Technical University Dresden, Dresden, Germany
| | - Elodie Chapuis
- MIVEGEC, Univ Montpellier, CNRS, IRD, Montpellier, France
| | - Stefania Meconcelli
- Centre d'Écologie Fonctionnelle et Évolutive, CNRS, Univ Montpellier, EPHE, IRD, Montpellier, France.,Department of Life Sciences and Systems Biology, Università di Torino, Torino, Italy
| | - Nicolas Bonel
- Centre d'Écologie Fonctionnelle et Évolutive, CNRS, Univ Montpellier, EPHE, IRD, Montpellier, France.,Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS-CCT-CONICET Bahía Blanca), Bahía Blanca, Argentina
| | - Boris Delahaie
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Patrice David
- Centre d'Écologie Fonctionnelle et Évolutive, CNRS, Univ Montpellier, EPHE, IRD, Montpellier, France
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3
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Qin X, Yang J, Ma J, Lock TR, Wang G, Zhang Z. Precopulatory oral sex contact plays an important role in copulatory success in a cryptic desert beetle. Ecol Evol 2021; 11:12285-12293. [PMID: 34594499 PMCID: PMC8462132 DOI: 10.1002/ece3.6595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 06/11/2020] [Accepted: 06/29/2020] [Indexed: 11/07/2022] Open
Abstract
Precopulatory courtship plays an essential role in the insemination process and influences postcopulatory behavior between males and females. Male precopulatory oral stimulation of female genitals is rare for invertebrates. Here, we describe an intriguing oral sexual courtship in a cryptic desert beetle Platyope mongolica Faldermann. The males repeatedly contact the female's genitals using their mouths to gain consent to mate. Furthermore, the rate at which males contact the female's genitals relates to the copulation success in a series of observations. However, interference in oral sexual contacts decreased the proportion of successful copulation. Further no-choice tests found homosexual behavior between males with antenna removed. We report the precopulatory oral sexual behavior and its important role for copulation success in P. mongolica for the first time. These findings highlight the significance of oral sexual courtship in sexual selection.
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Affiliation(s)
- Xinghu Qin
- Institute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
- School of BiologyUniversity of St AndrewsSt AndrewsUK
- Scientific Observation and Experimental Station of Pests in Xilingol RangelandMinistry of AgricultureXilinhotChina
| | - Jinshu Yang
- Institute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
- Scientific Observation and Experimental Station of Pests in Xilingol RangelandMinistry of AgricultureXilinhotChina
| | - Jingchuan Ma
- Institute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
- Scientific Observation and Experimental Station of Pests in Xilingol RangelandMinistry of AgricultureXilinhotChina
| | | | - Guangjun Wang
- Institute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
- Scientific Observation and Experimental Station of Pests in Xilingol RangelandMinistry of AgricultureXilinhotChina
| | - Zehua Zhang
- Institute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
- Scientific Observation and Experimental Station of Pests in Xilingol RangelandMinistry of AgricultureXilinhotChina
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4
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Wiberg RAW, Veltsos P, Snook RR, Ritchie MG. Experimental evolution supports signatures of sexual selection in genomic divergence. Evol Lett 2021; 5:214-229. [PMID: 34136270 PMCID: PMC8190450 DOI: 10.1002/evl3.220] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 02/13/2021] [Accepted: 02/14/2021] [Indexed: 12/13/2022] Open
Abstract
Comparative genomics has contributed to the growing evidence that sexual selection is an important component of evolutionary divergence and speciation. Divergence by sexual selection is implicated in faster rates of divergence of the X chromosome and of genes thought to underlie sexually selected traits, including genes that are sex biased in expression. However, accurately inferring the relative importance of complex and interacting forms of natural selection, demography, and neutral processes that occurred in the evolutionary past is challenging. Experimental evolution provides an opportunity to apply controlled treatments for multiple generations and examine the consequent genomic divergence. Here, we altered sexual selection intensity, elevating sexual selection in polyandrous lines and eliminating it in monogamous lines, and examined patterns of allele frequency divergence in the genome of Drosophila pseudoobscura after more than 160 generations of experimental evolution. Divergence is not uniform across the genome but concentrated in "islands," many of which contain candidate genes implicated in mating behaviors and other sexually selected phenotypes. These are more often seen on the X chromosome, which also shows greater divergence in F ST than neutral expectations. There are characteristic signatures of selection seen in these regions, with lower diversity on the X chromosome than the autosomes, and differences in diversity on the autosomes between selection regimes. Reduced Tajima's D within some of the divergent regions may imply that selective sweeps have occurred, despite considerable recombination. These changes are associated with both differential gene expression between the lines and sex-biased gene expression within the lines. Our results are very similar to those thought to implicate sexual selection in divergence between species and natural populations, and hence provide experimental support for the likely role of sexual selection in driving such types of genetic divergence, but also illustrate how variable outcomes can be for different genomic regions.
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Affiliation(s)
- R. Axel W. Wiberg
- Centre for Biological DiversityUniversity of St AndrewsSt AndrewsKY16 9THUnited Kingdom
- Current Address: Department of Environmental SciencesZoological InstituteUniversity of BaselBaselCH‐4051Switzerland
| | - Paris Veltsos
- Department of Ecology and Evolutionary BiologyUniversity of KansasLawrenceKansas66045
| | - Rhonda R. Snook
- Department of ZoologyStockholm UniversityStockholm106 91Sweden
| | - Michael G. Ritchie
- Centre for Biological DiversityUniversity of St AndrewsSt AndrewsKY16 9THUnited Kingdom
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5
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Can Sexual Selection Drive the Evolution of Sperm Cell Structure? Cells 2021; 10:cells10051227. [PMID: 34067752 PMCID: PMC8156441 DOI: 10.3390/cells10051227] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 05/04/2021] [Accepted: 05/14/2021] [Indexed: 02/07/2023] Open
Abstract
Sperm cells have undergone an extraordinarily divergent evolution among metazoan animals. Parker recognized that because female animals frequently mate with more than one male, sexual selection would continue after mating and impose strong selection on sperm cells to maximize fertilization success. Comparative analyses among species have revealed a general relationship between the strength of selection from sperm competition and the length of sperm cells and their constituent parts. However, comparative analyses cannot address causation. Here, we use experimental evolution to ask whether sexual selection can drive the divergence of sperm cell phenotype, using the dung beetle Onthophagus taurus as a model. We either relaxed sexual selection by enforcing monogamy or allowed sexual selection to continue for 20 generations before sampling males and measuring the total length of sperm cells and their constituent parts, the acrosome, nucleus, and flagella. We found differences in the length of the sperm cell nucleus but no differences in the length of the acrosome, flagella, or total sperm length. Our data suggest that different sperm cell components may respond independently to sexual selection and contribute to the divergent evolution of these extraordinary cells.
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6
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Strategic adjustment of ejaculate quality in response to variation of the socio-sexual environment. Behav Ecol Sociobiol 2021. [DOI: 10.1007/s00265-021-03032-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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7
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Giannakara A, Ramm SA. Evidence for inter-population variation in waiting times in a self-fertilizing flatworm. INVERTEBR REPROD DEV 2020. [DOI: 10.1080/07924259.2020.1732485] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
| | - Steven A. Ramm
- Evolutionary Biology, Bielefeld University, Bielefeld, Germany
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8
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Singh P, Vellnow N, Schärer L. Variation in sex allocation plasticity in three closely related flatworm species. Ecol Evol 2020; 10:26-37. [PMID: 31988714 PMCID: PMC6972800 DOI: 10.1002/ece3.5566] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 07/15/2019] [Accepted: 07/28/2019] [Indexed: 01/15/2023] Open
Abstract
Sex allocation (SA) theory for simultaneous hermaphrodites predicts an influence of group size on SA. Since group size can vary within an individual's lifetime, this can favor the evolution of phenotypically plastic SA. In an emerging comparative context, we here report on SA plasticity in three closely related Macrostomum flatworm species, namely Macrostomum janickei, Macrostomum cliftonensis, and Macrostomum mirumnovem. For each species, we experimentally raised worms in three group sizes (isolated, pairs, and octets) and two enclosure sizes (small and large) in all factorial combinations and studied the effects of these factors on different estimates of SA. In addition, we also evaluated whether isolated worms engage in self-fertilization. We found that all species have plastic SA, with M. cliftonensis being more plastic than the other two species, as assessed by comparing standardized effect sizes of (a) the presence/absence of mating partners and (b) the strength of sexual competition. Moreover, we found that sperm production rate-but not sperm morphology-is plastic in M. cliftonensis, and that only M. mirumnovem self-fertilized during our observation period. Our study suggests that both SA and SA plasticity can diverge even between closely related species.
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Affiliation(s)
- Pragya Singh
- Evolutionary BiologyZoological InstituteUniversity of BaselBaselSwitzerland
| | - Nikolas Vellnow
- Evolutionary BiologyZoological InstituteUniversity of BaselBaselSwitzerland
- Evolutionary Biology DepartmentBielefeld UniversityBielefeldGermany
| | - Lukas Schärer
- Evolutionary BiologyZoological InstituteUniversity of BaselBaselSwitzerland
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9
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Santi M, Picchi L, Lorenzi MC. Dynamic modulation of reproductive strategies in a simultaneous hermaphrodite and preference for the male role. Anim Behav 2018. [DOI: 10.1016/j.anbehav.2018.10.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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10
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Winkler L, Ramm SA. Experimental evidence for reduced male allocation under selfing in a simultaneously hermaphroditic animal. Biol Lett 2018; 14:rsbl.2018.0570. [PMID: 30305462 DOI: 10.1098/rsbl.2018.0570] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 09/15/2018] [Indexed: 11/12/2022] Open
Abstract
Self-fertilization is widespread among simultaneously hermaphroditic animals and plants, but is often only facultatively deployed under circumstances that constrain outcrossing. A central prediction of sex allocation (SA) theory is that because exclusive selfing reduces sperm or pollen competition to zero, this should favour extreme economy in resources channelled to the male sex function. We can therefore expect that organisms switching from outcrossing to selfing should reduce their male allocation. However, to date this prediction has received relatively little support in animal taxa, especially compared to plants. Here we show that isolated individuals (under enforced selfing conditions) have a less male-biased SA than do grouped conspecifics (under outcrossing conditions) in the preferentially outcrossing flatworm Macrostomum hystrix This shift arises from a reduced male allocation (testis area) in isolated individuals, although we did not find any evidence for a re-allocation of these resources to the female sex function (i.e. ovary area was unaffected by selfing/outcrossing conditions). Our results provide some of the clearest experimental evidence to date for reduced male allocation under selfing in simultaneously hermaphroditic animals, extending previous findings comparing SA between populations differing in selfing rates to the level of individual plasticity in gametogenesis.
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Affiliation(s)
- Lennart Winkler
- Department of Evolutionary Biology, Bielefeld University, Morgenbreede 45, 33615 Bielefeld, Germany
| | - Steven A Ramm
- Department of Evolutionary Biology, Bielefeld University, Morgenbreede 45, 33615 Bielefeld, Germany
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11
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Bonel N, Noël E, Janicke T, Sartori K, Chapuis E, Ségard A, Meconcelli S, Pélissié B, Sarda V, David P. Asymmetric evolutionary responses to sex-specific selection in a hermaphrodite. Evolution 2018; 72:2181-2201. [PMID: 30109706 DOI: 10.1111/evo.13565] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Accepted: 07/25/2018] [Indexed: 01/10/2023]
Abstract
Sex allocation theory predicts that simultaneous hermaphrodites evolve to an evolutionary stable resource allocation, whereby any increase in investment to male reproduction leads to a disproportionate cost on female reproduction and vice versa. However, empirical evidence for sexual trade-offs in hermaphroditic animals is still limited. Here, we tested how male and female reproductive traits evolved under conditions of reduced selection on either male or female reproduction for 40 generations in a hermaphroditic snail. This selection favors a reinvestment of resources from the sex function under relaxed selection toward the other function. We found no such evolutionary response. Instead, juvenile survival and male reproductive success significantly decreased in lines where selection on the male function (i.e., sexual selection) was relaxed, while relaxing selection on the female function had no effect. Our results suggest that most polymorphisms under selection in these lines were not sex-antagonistic. Rather, they were deleterious mutations affecting juvenile survival (thus reducing both male and female fitness) with strong pleiotropic effects on male success in a sexual selection context. These mutations accumulated when sexual selection was relaxed, which supports the idea that sexual selection in hermaphrodites contributes to purge the mutation load from the genome as in separate-sex organisms.
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Affiliation(s)
- Nicolás Bonel
- Laboratorio de Zoología de Invertebrados I, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, San Juan 670, B8000ICN, Bahía Blanca, CONICET, Argentina.,Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, Ecole Pratique des Hautes Etudes, 1919 Route de Mende, 34293 Montpellier Cedex 05, France
| | - Elsa Noël
- Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, Ecole Pratique des Hautes Etudes, 1919 Route de Mende, 34293 Montpellier Cedex 05, France.,Institute for Population Genetics, University of Veterinary Medicine, Veterinärplatz 1, A-1210, Vienna, Austria
| | - Tim Janicke
- Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, Ecole Pratique des Hautes Etudes, 1919 Route de Mende, 34293 Montpellier Cedex 05, France.,School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, United Kingdom
| | - Kevin Sartori
- Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, Ecole Pratique des Hautes Etudes, 1919 Route de Mende, 34293 Montpellier Cedex 05, France
| | - Elodie Chapuis
- Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, Ecole Pratique des Hautes Etudes, 1919 Route de Mende, 34293 Montpellier Cedex 05, France.,IRD, UMR186 Intéractions Plantes-Microrganismes-Environement, 911, Avenue Agropolis, BP 64501 34394 Montpellier Cedex 05, France.,CIRAD, UMR PVBMT, F-97410 St Pierre, La Réunion, France
| | - Adeline Ségard
- Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, Ecole Pratique des Hautes Etudes, 1919 Route de Mende, 34293 Montpellier Cedex 05, France
| | - Stefania Meconcelli
- Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, Ecole Pratique des Hautes Etudes, 1919 Route de Mende, 34293 Montpellier Cedex 05, France.,Department of Life Sciences and Systems Biology, Università di Torino, Turin, Italy
| | - Benjamin Pélissié
- University of Wisconsin Madison, Department of Entomology, 1630 Linden Dr, Madison, Wisconsin 53706
| | - Violette Sarda
- Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, Ecole Pratique des Hautes Etudes, 1919 Route de Mende, 34293 Montpellier Cedex 05, France
| | - Patrice David
- Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, Ecole Pratique des Hautes Etudes, 1919 Route de Mende, 34293 Montpellier Cedex 05, France
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12
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Vellnow N, Marie-Orleach L, Zadesenets KS, Schärer L. Bigger testes increase paternity in a simultaneous hermaphrodite, independently of the sperm competition level. J Evol Biol 2017; 31:180-196. [DOI: 10.1111/jeb.13212] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 10/31/2017] [Accepted: 11/14/2017] [Indexed: 12/12/2022]
Affiliation(s)
- N. Vellnow
- Zoological Institute, Evolutionary Biology; University of Basel; Basel Switzerland
| | | | | | - L. Schärer
- Zoological Institute, Evolutionary Biology; University of Basel; Basel Switzerland
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13
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Godwin JL, Vasudeva R, Michalczyk Ł, Martin OY, Lumley AJ, Chapman T, Gage MJG. Experimental evolution reveals that sperm competition intensity selects for longer, more costly sperm. Evol Lett 2017; 1:102-113. [PMID: 30283643 PMCID: PMC6089504 DOI: 10.1002/evl3.13] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 04/24/2017] [Accepted: 05/02/2017] [Indexed: 12/12/2022] Open
Abstract
It is the differences between sperm and eggs that fundamentally underpin the differences between the sexes within reproduction. For males, it is theorized that widespread sperm competition leads to selection for investment in sperm numbers, achieved by minimizing sperm size within limited resources for spermatogenesis in the testis. Here, we empirically examine how sperm competition shapes sperm size, after more than 77 generations of experimental selection of replicate lines under either high or low sperm competition intensities in the promiscuous flour beetle Tribolium castaneum. After this experimental evolution, populations had diverged significantly in their sperm competitiveness, with sperm in ejaculates from males evolving under high sperm competition intensities gaining 20% greater paternity than sperm in ejaculates from males that had evolved under low sperm competition intensity. Males did not change their relative investment into sperm production following this experimental evolution, showing no difference in testis sizes between high and low intensity regimes. However, the more competitive males from high sperm competition intensity regimes had evolved significantly longer sperm and, across six independently selected lines, there was a significant association between the degree of divergence in sperm length and average sperm competitiveness. To determine whether such sperm elongation is costly, we used dietary restriction experiments, and revealed that protein-restricted males produced significantly shorter sperm. Our findings therefore demonstrate that sperm competition intensity can exert positive directional selection on sperm size, despite this being a costly reproductive trait.
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Affiliation(s)
- Joanne L. Godwin
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUnited Kingdom
| | - Ramakrishnan Vasudeva
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUnited Kingdom
| | | | | | - Alyson J. Lumley
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUnited Kingdom
| | - Tracey Chapman
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUnited Kingdom
| | - Matthew J. G. Gage
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUnited Kingdom
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14
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Vellnow N, Vizoso DB, Viktorin G, Schärer L. No evidence for strong cytonuclear conflict over sex allocation in a simultaneously hermaphroditic flatworm. BMC Evol Biol 2017; 17:103. [PMID: 28427326 PMCID: PMC5397761 DOI: 10.1186/s12862-017-0952-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Accepted: 04/10/2017] [Indexed: 01/31/2023] Open
Abstract
Background Cytoplasmic sex allocation distorters, which arise from cytonuclear conflict over the optimal investment into male versus female reproductive function, are some of the best-researched examples for genomic conflict. Among hermaphrodites, many such distorters have been found in plants, while, to our knowledge, none have been clearly documented in animals. Methods Here we provide a quantitative test for cytonuclear conflict over sex allocation in the simultaneously hermaphroditic flatworm Macrostomum lignano. We used a quantitative genetic breeding design, employing pair-wise crosses of 2 × 15 independent inbred lines, to partition the phenotypic variance in several traits (including sex allocation) into its nuclear and cytoplasmic components. Results Although the nuclear genetic background had a significant effect on all traits analyzed, we found significant cytoplasmic genetic variation only for ovary size, there explaining just 4.1% of the variance. A subsequent statistical power analysis showed that the experimental design had considerable power to detect cytonuclear interactions. Conclusion We conclude that there were no strong effects of cytonuclear conflict in the studied populations, possibly because the usually compact mitochondrial genomes in animals have a lower evolvability than the large mitochondrial genomes in plants or because the sampled populations currently do not harbor variation at putative distorter and/or the restorer loci. Electronic supplementary material The online version of this article (doi:10.1186/s12862-017-0952-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Nikolas Vellnow
- University of Basel, Zoological Institute, Evolutionary Biology, Basel, Switzerland.
| | - Dita B Vizoso
- University of Basel, Zoological Institute, Evolutionary Biology, Basel, Switzerland.,University of Innsbruck, Institute of Zoology, Innsbruck, Austria
| | - Gudrun Viktorin
- University of Basel, Zoological Institute, Evolutionary Biology, Basel, Switzerland
| | - Lukas Schärer
- University of Basel, Zoological Institute, Evolutionary Biology, Basel, Switzerland.,University of Innsbruck, Institute of Zoology, Innsbruck, Austria
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15
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Giannakara A, Schärer L, Ramm SA. Sperm competition-induced plasticity in the speed of spermatogenesis. BMC Evol Biol 2016; 16:60. [PMID: 26956948 PMCID: PMC4784355 DOI: 10.1186/s12862-016-0629-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Accepted: 03/01/2016] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND Sperm competition between rival ejaculates over the fertilization of ova typically selects for the production of large numbers of sperm. An obvious way to increase sperm production is to increase testis size, and most empirical work has focussed on this parameter. Adaptive plasticity in sperm production rate could also arise due to variation in the speed with which each spermatozoon is produced, but whether animals can respond to relevant environmental conditions by modulating the kinetics of spermatogenesis in this way has not been experimentally investigated. RESULTS Here we demonstrate that the simultaneously hermaphroditic flatworm Macrostomum lignano exhibits substantial plasticity in the speed of spermatogenesis, depending on the social context: worms raised under higher levels of sperm competition produce sperm faster. CONCLUSIONS Our findings overturn the prevailing view that the speed of spermatogenesis is a static property of a genotype, and demonstrate the profound impact that social environmental conditions can exert upon a key developmental process. We thus identify, to our knowledge, a novel mechanism through which sperm production rate is maximised under sperm competition.
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Affiliation(s)
- Athina Giannakara
- Evolutionary Biology, Bielefeld University, Morgenbreede 45, 33615, Bielefeld, Germany.
| | - Lukas Schärer
- Evolutionary Biology, Zoological Institute, University of Basel, Vesalgasse 1, 4051, Basel, Switzerland.
| | - Steven A Ramm
- Evolutionary Biology, Bielefeld University, Morgenbreede 45, 33615, Bielefeld, Germany.
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