1
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Zhang H, Lundberg M, Ponnikas S, Hasselquist D, Hansson B. Male-biased recombination at chromosome ends in a songbird revealed by precisely mapping crossover positions. G3 (BETHESDA, MD.) 2024; 14:jkae150. [PMID: 38985659 PMCID: PMC11373659 DOI: 10.1093/g3journal/jkae150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Revised: 06/17/2024] [Accepted: 06/24/2024] [Indexed: 07/12/2024]
Abstract
Recombination plays a crucial role in evolution by generating novel haplotypes and disrupting linkage between genes, thereby enhancing the efficiency of selection. Here, we analyze the genomes of 12 great reed warblers (Acrocephalus arundinaceus) in a 3-generation pedigree to identify precise crossover positions along the chromosomes. We located more than 200 crossovers and found that these were highly concentrated toward the telomeric ends of the chromosomes. Apart from this major pattern in the recombination landscape, we found significantly higher frequencies of crossovers in genic compared with intergenic regions, and in exons compared with introns. Moreover, while the number of recombination events was similar between the sexes, the crossovers were located significantly closer to the ends of paternal compared with maternal chromosomes. In conclusion, our study of the great reed warbler revealed substantial variation in crossover frequencies within chromosomes, with a distinct bias toward the sub-telomeric regions, particularly on the paternal side. These findings emphasize the importance of thoroughly screening the entire length of chromosomes to characterize the recombination landscape and uncover potential sex-biases in recombination.
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Affiliation(s)
- Hongkai Zhang
- Department of Biology, Lund University, 22362 Lund, Sweden
| | - Max Lundberg
- Department of Biology, Lund University, 22362 Lund, Sweden
| | - Suvi Ponnikas
- Department of Biology, University of Oulu, 90570 Oulu, Finland
| | | | - Bengt Hansson
- Department of Biology, Lund University, 22362 Lund, Sweden
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2
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Muralidhar P, Coop G. Polygenic response of sex chromosomes to sexual antagonism. Evolution 2024; 78:539-554. [PMID: 38153370 PMCID: PMC10903542 DOI: 10.1093/evolut/qpad231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 11/30/2023] [Accepted: 12/22/2023] [Indexed: 12/29/2023]
Abstract
Sexual antagonism occurs when males and females differ in their phenotypic fitness optima but are constrained in their evolution to these optima because of their shared genome. The sex chromosomes, which have distinct evolutionary "interests" relative to the autosomes, are theorized to play an important role in sexually antagonistic conflict. However, the evolutionary responses of sex chromosomes and autosomes have usually been considered independently, that is, via contrasting the response of a gene located on either an X chromosome or an autosome. Here, we study the coevolutionary response of the X chromosome and autosomes to sexually antagonistic selection acting on a polygenic phenotype. We model a phenotype initially under stabilizing selection around a single optimum, followed by a sudden divergence of the male and female optima. We find that, in the absence of dosage compensation, the X chromosome promotes evolution toward the female optimum, inducing coevolutionary male-biased responses on the autosomes. Dosage compensation obscures the female-biased interests of the X, causing it to contribute equally to male and female phenotypic change. We further demonstrate that fluctuations in an adaptive landscape can generate prolonged intragenomic conflict and accentuate the differential responses of the X and autosomes to this conflict.
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Affiliation(s)
- Pavitra Muralidhar
- Center for Population Biology, University of California, Davis, CA, United States
- Department of Evolution and Ecology, University of California, Davis, CA, United States
- Department of Ecology and Evolution, University of Chicago, Chicago, IL, United States
| | - Graham Coop
- Center for Population Biology, University of California, Davis, CA, United States
- Department of Evolution and Ecology, University of California, Davis, CA, United States
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3
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Gatto KP, Timoshevskaya N, Smith JJ, Lourenço LB. Sequencing of laser captured Z and W chromosomes of the tocantins paradoxical frog (Pseudis tocantins) provides insights on repeatome and chromosomal homology. J Evol Biol 2022; 35:1659-1674. [PMID: 35642451 DOI: 10.1111/jeb.14027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 04/06/2022] [Accepted: 05/09/2022] [Indexed: 11/30/2022]
Abstract
Pseudis tocantins is the only frog species of the hylid genus Pseudis that possesses highly heteromorphic sex chromosomes. Z and W chromosomes of Ps. tocantins differ in size, morphology, position of the nucleolar organizer region (NOR) and the amount and distribution of heterochromatin. A chromosomal inversion and heterochromatin amplification on the W chromosome were previously inferred to be involved in the evolution of this sex chromosome pair. Despite these findings, knowledge related to the molecular composition of the large heterochromatic band of this W chromosome is restricted to the PcP190 satellite DNA, and no data are available regarding the gene content of either the W or the Z chromosome of Ps. tocantins. Here, we sequenced microdissected Z and W chromosomes of this species to further resolve their molecular composition. Comparative genomic analysis suggests that Ps. tocantins sex chromosomes are likely homologous to chromosomes 4 and 10 of Xenopus tropicalis. Analyses of the repetitive DNA landscape in the Z and W assemblies allowed for the identification of several transposable elements and putative satellite DNA sequences. Finally, some transposable elements from the W assembly were found to be highly diverse and divergent from elements found elsewhere in the genome, suggesting a rapid amplification of these elements on the W chromosome.
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Affiliation(s)
- Kaleb Pretto Gatto
- Laboratory of Chromosome Studies, Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas, Brazil.,Laboratory of Herpetology and Aquaculture Center, Department of Zoology, Institute of Biosciences, São Paulo State University, Rio Claro, Brazil
| | - Nataliya Timoshevskaya
- Department of Biology, College of Arts and Sciences, University of Kentucky, Lexington, Kentucky, USA
| | - Jeramiah J Smith
- Department of Biology, College of Arts and Sciences, University of Kentucky, Lexington, Kentucky, USA
| | - Luciana Bolsoni Lourenço
- Laboratory of Chromosome Studies, Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas, Brazil
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4
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Perrin N. Sex-chromosome evolution in frogs: what role for sex-antagonistic genes? Philos Trans R Soc Lond B Biol Sci 2021; 376:20200094. [PMID: 34247502 PMCID: PMC8273499 DOI: 10.1098/rstb.2020.0094] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/08/2020] [Indexed: 02/07/2023] Open
Abstract
Sex-antagonistic (SA) genes are widely considered to be crucial players in the evolution of sex chromosomes, being instrumental in the arrest of recombination and degeneration of Y chromosomes, as well as important drivers of sex-chromosome turnovers. To test such claims, one needs to focus on systems at the early stages of differentiation, ideally with a high turnover rate. Here, I review recent work on two families of amphibians, Ranidae (true frogs) and Hylidae (tree frogs), to show that results gathered so far from these groups provide no support for a significant role of SA genes in the evolutionary dynamics of their sex chromosomes. The findings support instead a central role for neutral processes and deleterious mutations. This article is part of the theme issue 'Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part I)'.
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Affiliation(s)
- Nicolas Perrin
- Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland
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5
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Charlesworth D, Zhang Y, Bergero R, Graham C, Gardner J, Yong L. Using GC Content to Compare Recombination Patterns on the Sex Chromosomes and Autosomes of the Guppy, Poecilia reticulata, and Its Close Outgroup Species. Mol Biol Evol 2021; 37:3550-3562. [PMID: 32697821 DOI: 10.1093/molbev/msaa187] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Genetic and physical mapping of the guppy (Poecilia reticulata) have shown that recombination patterns differ greatly between males and females. Crossover events occur evenly across the chromosomes in females, but in male meiosis they are restricted to the tip furthest from the centromere of each chromosome, creating very high recombination rates per megabase, as in pseudoautosomal regions of mammalian sex chromosomes. We used GC content to indirectly infer recombination patterns on guppy chromosomes, based on evidence that recombination is associated with GC-biased gene conversion, so that genome regions with high recombination rates should be detectable by high GC content. We used intron sequences and third positions of codons to make comparisons between sequences that are matched, as far as possible, and are all probably under weak selection. Almost all guppy chromosomes, including the sex chromosome (LG12), have very high GC values near their assembly ends, suggesting high recombination rates due to strong crossover localization in male meiosis. Our test does not suggest that the guppy XY pair has stronger crossover localization than the autosomes, or than the homologous chromosome in the close relative, the platyfish (Xiphophorus maculatus). We therefore conclude that the guppy XY pair has not recently undergone an evolutionary change to a different recombination pattern, or reduced its crossover rate, but that the guppy evolved Y-linkage due to acquiring a male-determining factor that also conferred the male crossover pattern. We also identify the centromere ends of guppy chromosomes, which were not determined in the genome assembly.
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Affiliation(s)
- Deborah Charlesworth
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Yexin Zhang
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Roberta Bergero
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Chay Graham
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Jim Gardner
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Lengxob Yong
- Centre for Ecology and Conservation, University of Exeter, Falmouth, Cornwall, United Kingdom
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6
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Furman BLS, Cauret CMS, Knytl M, Song XY, Premachandra T, Ofori-Boateng C, Jordan DC, Horb ME, Evans BJ. A frog with three sex chromosomes that co-mingle together in nature: Xenopus tropicalis has a degenerate W and a Y that evolved from a Z chromosome. PLoS Genet 2020; 16:e1009121. [PMID: 33166278 PMCID: PMC7652241 DOI: 10.1371/journal.pgen.1009121] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 09/16/2020] [Indexed: 11/18/2022] Open
Abstract
In many species, sexual differentiation is a vital prelude to reproduction, and disruption of this process can have severe fitness effects, including sterility. It is thus interesting that genetic systems governing sexual differentiation vary among-and even within-species. To understand these systems more, we investigated a rare example of a frog with three sex chromosomes: the Western clawed frog, Xenopus tropicalis. We demonstrate that natural populations from the western and eastern edges of Ghana have a young Y chromosome, and that a male-determining factor on this Y chromosome is in a very similar genomic location as a previously known female-determining factor on the W chromosome. Nucleotide polymorphism of expressed transcripts suggests genetic degeneration on the W chromosome, emergence of a new Y chromosome from an ancestral Z chromosome, and natural co-mingling of the W, Z, and Y chromosomes in the same population. Compared to the rest of the genome, a small sex-associated portion of the sex chromosomes has a 50-fold enrichment of transcripts with male-biased expression during early gonadal differentiation. Additionally, X. tropicalis has sex-differences in the rates and genomic locations of recombination events during gametogenesis that are similar to at least two other Xenopus species, which suggests that sex differences in recombination are genus-wide. These findings are consistent with theoretical expectations associated with recombination suppression on sex chromosomes, demonstrate that several characteristics of old and established sex chromosomes (e.g., nucleotide divergence, sex biased expression) can arise well before sex chromosomes become cytogenetically distinguished, and show how these characteristics can have lingering consequences that are carried forward through sex chromosome turnovers.
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Affiliation(s)
- Benjamin L. S. Furman
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada
- Department of Zoology, University of British Columbia, 6270 University Blvd Vancouver, British Columbia, V6T 1Z4 Canada
| | - Caroline M. S. Cauret
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada
| | - Martin Knytl
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada
- Department of Cell Biology, Charles University, 7 Vinicna Street, Prague, 12843, Czech Republic
| | - Xue-Ying Song
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada
| | - Tharindu Premachandra
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada
| | | | - Danielle C. Jordan
- Eugene Bell Center for Regenerative Biology and Tissue Engineering and National Xenopus Resource, Marine Biological Laboratory, 7 MBL St, Woods Hole, MA 02543 USA
| | - Marko E. Horb
- Eugene Bell Center for Regenerative Biology and Tissue Engineering and National Xenopus Resource, Marine Biological Laboratory, 7 MBL St, Woods Hole, MA 02543 USA
| | - Ben J. Evans
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada
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7
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From molecules to populations: appreciating and estimating recombination rate variation. Nat Rev Genet 2020; 21:476-492. [DOI: 10.1038/s41576-020-0240-1] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/15/2020] [Indexed: 02/07/2023]
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8
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Molecular and evolutionary dynamics of animal sex-chromosome turnover. Nat Ecol Evol 2019; 3:1632-1641. [DOI: 10.1038/s41559-019-1050-8] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 10/24/2019] [Indexed: 11/08/2022]
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9
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Muralidhar P. Mating preferences of selfish sex chromosomes. Nature 2019; 570:376-379. [PMID: 31168095 DOI: 10.1038/s41586-019-1271-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 05/08/2019] [Indexed: 11/09/2022]
Abstract
The evolution of female mating preferences for harmful male traits is a central paradox of sexual selection1-9. Two dominant explanations for this paradox8,10 are Fisher's runaway process, which is based on genetic correlations between preference and trait1,3,4, and Zahavi's handicap principle, in which the trait is an honest costly signal of male quality2,6,8,11. However, both of these explanations require the exogenous initial spread of female preferences before harmful male traits can evolve1-4,6,8,11. Here I present a mechanism for the evolution of female mating preferences for harmful male traits that is based on the selfish evolutionary interests of sex chromosomes. I demonstrate that female-biased genetic elements-such as the W and X sex chromosomes-will evolve mating preferences for males who display traits that reduce their fitness and/or that of their male offspring, but increase fitness in female offspring. In particular, W-linked preferences can cause nearly lethal male traits to sweep to fixation. Sex-linked preferences can drive the evolution of traits such as ornamental handicaps and male parental care, and can explain variation in ornamentation and behaviour across taxa with divergent sex-determining mechanisms.
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Affiliation(s)
- Pavitra Muralidhar
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA. .,Program for Evolutionary Dynamics, Harvard University, Cambridge, MA, USA.
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10
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Exaggerated heterochiasmy in a fish with sex-linked male coloration polymorphisms. Proc Natl Acad Sci U S A 2019; 116:6924-6931. [PMID: 30894479 DOI: 10.1073/pnas.1818486116] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
It is often stated that polymorphisms for mutations affecting fitness of males and females in opposite directions [sexually antagonistic (SA) polymorphisms] are the main selective force for the evolution of recombination suppression between sex chromosomes. However, empirical evidence to discriminate between different hypotheses is difficult to obtain. We report genetic mapping results in laboratory-raised families of the guppy (Poecilia reticulata), a sexually dimorphic fish with SA polymorphisms for male coloration genes, mostly on the sex chromosomes. Comparison of the genetic and physical maps shows that crossovers are distributed very differently in the two sexes (heterochiasmy); in male meiosis, they are restricted to the termini of all four chromosomes studied, including chromosome 12, which carries the sex-determining locus. Genome resequencing of male and female guppies from a population also indicates sex linkage of variants across almost the entire chromosome 12. More than 90% of the chromosome carrying the male-determining locus is therefore transmitted largely through the male lineage. A lack of heterochiasmy in a related fish species suggests that it originated recently in the lineage leading to the guppy. Our findings do not support the hypothesis that suppressed recombination evolved in response to the presence of SA polymorphisms. Instead, a low frequency of recombination on a chromosome that carries a male-determining locus and has not undergone genetic degeneration has probably facilitated the establishment of male-beneficial coloration polymorphisms.
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11
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Gerchen JF, Dufresnes C, Stöck M. Introgression across Hybrid Zones Is Not Mediated by Large X-Effects in Green Toads with Undifferentiated Sex Chromosomes. Am Nat 2018; 192:E178-E188. [DOI: 10.1086/699162] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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12
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Hill PL, Burridge CP, Ezaz T, Wapstra E. Conservation of Sex-Linked Markers among Conspecific Populations of a Viviparous Skink, Niveoscincus ocellatus, Exhibiting Genetic and Temperature-Dependent Sex Determination. Genome Biol Evol 2018; 10:1079-1087. [PMID: 29659810 PMCID: PMC5905450 DOI: 10.1093/gbe/evy042] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/01/2018] [Indexed: 12/18/2022] Open
Abstract
Sex determination systems are exceptionally diverse and have undergone multiple and independent evolutionary transitions among species, particularly reptiles. However, the mechanisms underlying these transitions have not been established. Here, we tested for differences in sex-linked markers in the only known reptile that is polymorphic for sex determination system, the spotted snow skink, Niveoscincus ocellatus, to quantify the genomic differences that have accompanied this transition. In a highland population, sex is determined genetically, whereas in a lowland population, offspring sex ratio is influenced by temperature. We found a similar number of sex-linked loci in each population, including shared loci, with genotypes consistent with male heterogamety (XY). However, population-specific linkage disequilibrium suggests greater differentiation of sex chromosomes in the highland population. Our results suggest that transitions between sex determination systems can be facilitated by subtle genetic differences.
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Affiliation(s)
- Peta L Hill
- School of Biological Sciences, University of Tasmania, Sandy Bay, Tasmania, Australia
| | | | - Tariq Ezaz
- Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, Australia
| | - Erik Wapstra
- School of Biological Sciences, University of Tasmania, Sandy Bay, Tasmania, Australia
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13
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Furman BLS, Evans BJ. Divergent Evolutionary Trajectories of Two Young, Homomorphic, and Closely Related Sex Chromosome Systems. Genome Biol Evol 2018; 10:742-755. [PMID: 29608717 PMCID: PMC5841384 DOI: 10.1093/gbe/evy045] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/20/2018] [Indexed: 02/02/2023] Open
Abstract
There exists extraordinary variation among species in the degree and nature of sex chromosome divergence. However, much of our knowledge about sex chromosomes is based on comparisons between deeply diverged species with different ancestral sex chromosomes, making it difficult to establish how fast and why sex chromosomes acquire variable levels of divergence. To address this problem, we studied sex chromosome evolution in two species of African clawed frog (Xenopus), both of whom acquired novel systems for sex determination from a recent common ancestor, and both of whom have female (ZW/ZZ) heterogamy. Derived sex chromosomes of one species, X. laevis, have a small region of suppressed recombination that surrounds the sex determining locus, and have remained this way for millions of years. In the other species, X. borealis, a younger sex chromosome system exists on a different pair of chromosomes, but the region of suppressed recombination surrounding an unidentified sex determining gene is vast, spanning almost half of the sex chromosomes. Differences between these sex chromosome systems are also apparent in the extent of nucleotide divergence between the sex chromosomes carried by females. Our analyses also indicate that in autosomes of both of these species, recombination during oogenesis occurs more frequently and in different genomic locations than during spermatogenesis. These results demonstrate that new sex chromosomes can assume radically different evolutionary trajectories, with far-reaching genomic consequences. They also suggest that in some instances the origin of new triggers for sex determination may be coupled with rapid evolution sex chromosomes, including recombination suppression of large genomic regions.
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Affiliation(s)
| | - Ben J Evans
- Department of Biology, McMaster University, Hamilton, Ontario, Canada
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14
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Lourenço de Freitas N, Al-Rikabi ABH, Bertollo LAC, Ezaz T, Yano CF, Aguiar de Oliveira E, Hatanaka T, Cioffi MDB. Early Stages of XY Sex Chromosomes Differentiation in the Fish Hoplias malabaricus (Characiformes, Erythrinidae) Revealed by DNA Repeats Accumulation. Curr Genomics 2018; 19:216-226. [PMID: 29606909 PMCID: PMC5850510 DOI: 10.2174/1389202918666170711160528] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 01/27/2017] [Accepted: 01/30/2017] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Species with 'young' or nascent sex chromosomes provide unique opportunities to understand early evolutionary mechanisms (e.g. accumulation of repetitive sequences, cessation of recombination and gene loss) that drive the evolution of sex chromosomes. Among vertebrates, fishes exhibit highly diverse and a wide spectrum of sex-determining mechanisms and sex chromosomes, ranging from cryptic to highly differentiated ones, as well as, from simple to multiple sex chromosome systems. Such variability in sex chromosome morphology and composition not only exists within closely related taxa, but often within races/populations of the same species. Inside this context, the wolf fish Hoplias malabaricus offers opportunity to investigate the evolution of morphologically variable sex chromosomes within a species complex, as homomorphic to highly differentiated sex chromosome systems occur among its different karyomorphs. MATERIALS & METHODS To discover various evolutionary stages of sex chromosomes and to compare their sequence composition among the wolf fish´s karyomorphs, we applied multipronged molecular cytogenetic approaches, including C-banding, repetitive DNAs mapping, Comparative Genomic Hybridization (CGH) and Whole Chromosomal Painting (WCP). Our study was able to characterize a cryptically differentiated XX/XY sex chromosome system in the karyomorph F of this species. CONCLUSION The Y chromosome was clearly identified by an interstitial heterochromatic block on the short arms, primarily composed of microsatellite motifs and retrotransposons. Additionally, CGH also identified a male specific chromosome region in the same chromosomal location, implying that the accumulation of these repeats may have initiated the Y chromosome differentiation, as well as played a critical role towards the evolution and differentiation of sex chromosomes in various karyomorphs of this species.
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Affiliation(s)
| | - Ahmed Basheer Hamid Al-Rikabi
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, Brazil
- Jena University Hospital, Friedrich Schiller University, Institute of Human Genetics, Kollegiengasse 10, D-07743Jena, Germany
| | | | - Tariq Ezaz
- Institute for Applied Ecology, University of Canberra, Canberra, Australia
| | - Cassia Fernanda Yano
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, Brazil
| | | | - Terumi Hatanaka
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, Brazil
| | - Marcelo de Bello Cioffi
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, Brazil
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15
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Haag CR, Theodosiou L, Zahab R, Lenormand T. Low recombination rates in sexual species and sex-asex transitions. Philos Trans R Soc Lond B Biol Sci 2017; 372:20160461. [PMID: 29109224 PMCID: PMC5698623 DOI: 10.1098/rstb.2016.0461] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/24/2017] [Indexed: 12/11/2022] Open
Abstract
In most sexual, diploid eukaryotes, at least one crossover occurs between each pair of homologous chromosomes during meiosis, presumably in order to ensure proper segregation. Well-known exceptions to this rule are species in which one sex does not recombine and specific chromosomes lacking crossover. We review other possible exceptions, including species with chromosome maps of less than 50 cM in one or both sexes. We discuss the idea that low recombination rates may favour sex-asex transitions, or, alternatively may be a consequence of it. We then show that a yet undescribed species of brine shrimp Artemia from Kazakhstan (A sp. Kazakhstan), the closest known relative of the asexual Artemia parthenogenetica, has one of the shortest genetic linkage maps known. Based on a family of 42 individuals and 589 RAD markers, we find that many linkage groups are considerably shorter than 50 cM, suggesting either no obligate crossover or crossovers concentrated at terminal positions with little effect on recombination. We contrast these findings with the published map of the more distantly related sexual congener, A. franciscana, and conclude that the study of recombination in non-model systems is important to understand the evolutionary causes and consequences of recombination.This article is part of the themed issue 'Evolutionary causes and consequences of recombination rate variation in sexual organisms'.
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Affiliation(s)
- Christoph R Haag
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE)-Unité Mixte de Recherche 5175, Centre National de la Recherche Scientifique (CNRS), Université de Montpellier-Université Paul-Valéry Montpellier-École Pratique des Hautes Études, 1919 Route de Mende, 34293 Montpellier Cedex 5, France
| | - Loukas Theodosiou
- Research Group for Community Dynamics, Max Planck Institute for Evolutionary Biology, August-Thienemann-Straße 2, 24306 Plön, Germany
| | - Roula Zahab
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE)-Unité Mixte de Recherche 5175, Centre National de la Recherche Scientifique (CNRS), Université de Montpellier-Université Paul-Valéry Montpellier-École Pratique des Hautes Études, 1919 Route de Mende, 34293 Montpellier Cedex 5, France
| | - Thomas Lenormand
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE)-Unité Mixte de Recherche 5175, Centre National de la Recherche Scientifique (CNRS), Université de Montpellier-Université Paul-Valéry Montpellier-École Pratique des Hautes Études, 1919 Route de Mende, 34293 Montpellier Cedex 5, France
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16
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Sutherland BJG, Rico C, Audet C, Bernatchez L. Sex Chromosome Evolution, Heterochiasmy, and Physiological QTL in the Salmonid Brook Charr Salvelinus fontinalis. G3 (BETHESDA, MD.) 2017; 7:2749-2762. [PMID: 28626004 PMCID: PMC5555479 DOI: 10.1534/g3.117.040915] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 06/13/2017] [Indexed: 02/06/2023]
Abstract
Whole-genome duplication (WGD) can have large impacts on genome evolution, and much remains unknown about these impacts. This includes the mechanisms of coping with a duplicated sex determination system and whether this has an impact on increasing the diversity of sex determination mechanisms. Other impacts include sexual conflict, where alleles having different optimums in each sex can result in sequestration of genes into nonrecombining sex chromosomes. Sex chromosome development itself may involve sex-specific recombination rate (i.e., heterochiasmy), which is also poorly understood. The family Salmonidae is a model system for these phenomena, having undergone autotetraploidization and subsequent rediploidization in most of the genome at the base of the lineage. The salmonid master sex determining gene is known, and many species have nonhomologous sex chromosomes, putatively due to transposition of this gene. In this study, we identify the sex chromosome of Brook Charr Salvelinus fontinalis and compare sex chromosome identities across the lineage (eight species and four genera). Although nonhomology is frequent, homologous sex chromosomes and other consistencies are present in distantly related species, indicating probable convergence on specific sex and neo-sex chromosomes. We also characterize strong heterochiasmy with 2.7-fold more crossovers in maternal than paternal haplotypes with paternal crossovers biased to chromosome ends. When considering only rediploidized chromosomes, the overall heterochiasmy trend remains, although with only 1.9-fold more recombination in the female than the male. Y chromosome crossovers are restricted to a single end of the chromosome, and this chromosome contains a large interspecific inversion, although its status between males and females remains unknown. Finally, we identify quantitative trait loci (QTL) for 21 unique growth, reproductive, and stress-related phenotypes to improve knowledge of the genetic architecture of these traits important to aquaculture and evolution.
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Affiliation(s)
- Ben J G Sutherland
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec G1V 0A6, Canada
| | - Ciro Rico
- School of Marine Studies, Molecular Diagnostics Laboratory, University of the South Pacific, Suva, Fiji
- Department of Wetland Ecology, Estación Biológica de Doñana (EBD-CSIC), 41092 Sevilla, Spain
| | - Céline Audet
- Institut des Sciences de la Mer de Rimouski, Université du Québec à Rimouski, Quebec G5L 3A1, Canada
| | - Louis Bernatchez
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec G1V 0A6, Canada
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17
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Variation in Recombination Rate: Adaptive or Not? Trends Genet 2017; 33:364-374. [DOI: 10.1016/j.tig.2017.03.003] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 03/06/2017] [Accepted: 03/07/2017] [Indexed: 01/30/2023]
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Comparative High-Density Linkage Mapping Reveals Conserved Genome Structure but Variation in Levels of Heterochiasmy and Location of Recombination Cold Spots in the Common Frog. G3-GENES GENOMES GENETICS 2017; 7:637-645. [PMID: 28040782 PMCID: PMC5295608 DOI: 10.1534/g3.116.036459] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
By combining 7077 SNPs and 61 microsatellites, we present the first linkage map for some of the early diverged lineages of the common frog, Rana temporaria, and the densest linkage map to date for this species. We found high homology with the published linkage maps of the Eastern and Western lineages but with differences in the order of some markers. Homology was also strong with the genome of the Tibetan frog Nanorana parkeri and we found high synteny with the clawed frog Xenopus tropicalis. We confirmed marked heterochiasmy between sexes and detected nonrecombining regions in several groups of the male linkage map. Contrary to the expectations set by the male heterogamety of the common frog, we did not find male heterozygosity excess in the chromosome previously shown to be linked to sex determination. Finally, we found blocks of loci showing strong transmission ratio distortion. These distorted genomic regions might be related to genetic incompatibilities between the parental populations, and are promising candidates for further investigation into the genetic basis of speciation and adaptation in the common frog.
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Brelsford A, Dufresnes C, Perrin N. Trans-species variation in Dmrt1 is associated with sex determination in four European tree-frog species. Evolution 2016; 70:840-7. [PMID: 26920488 DOI: 10.1111/evo.12891] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 01/26/2016] [Accepted: 02/01/2016] [Indexed: 01/15/2023]
Abstract
Empirical studies on the relative roles of occasional XY recombination versus sex-chromosome turnover in preventing sex-chromosome differentiation may shed light on the evolutionary forces acting on sex-determination systems. Signatures of XY recombination are difficult to distinguish from those of homologous transitions (i.e., transitions in sex-determination systems that keep sex-chromosome identity): both models predict X and Y alleles at sex-linked genes to cluster by species. However, the XY-recombination model specifically predicts the reverse pattern (clustering by gametologs) for those genes that are directly involved in sex determination. Hence, the latter model can only be validated by identification of an ancestral sex-determining region (SDR) with trans-species polymorphism associated to sex. Here we combine a candidate-gene approach with a genome scan to identify a small SDR shared by four species of a monophyletic clade of European tree frogs. This SDR encompasses at least the N-terminal part of Dmrt1 and immediate upstream sequences. Our findings provide definitive evidence that sex-chromosome homomorphy in this clade results only from XY recombination, and take an important step toward the identification of the sex-determining locus. Moreover, the sex-diagnostic markers we identify will enable research on environmental sex reversal in a wider range of frog species.
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Affiliation(s)
- Alan Brelsford
- Department of Ecology and Evolution, University of Lausanne, 1015, Lausanne, Switzerland. .,Biology Department, University of California, Riverside, California, 92521.
| | - Christophe Dufresnes
- Department of Ecology and Evolution, University of Lausanne, 1015, Lausanne, Switzerland
| | - Nicolas Perrin
- Department of Ecology and Evolution, University of Lausanne, 1015, Lausanne, Switzerland
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20
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Brelsford A, Rodrigues N, Perrin N. High-density linkage maps fail to detect any genetic component to sex determination in a Rana temporaria family. J Evol Biol 2015; 29:220-5. [PMID: 26404414 DOI: 10.1111/jeb.12747] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 08/25/2015] [Accepted: 08/31/2015] [Indexed: 01/16/2023]
Abstract
Sex chromosome differentiation in Rana temporaria varies strikingly among populations or families: whereas some males display well-differentiated Y haplotypes at microsatellite markers on linkage group 2 (LG2), others are genetically undistinguishable from females. We analysed with RADseq markers one family from a Swiss lowland population with no differentiated sex chromosomes, and where sibship analyses had failed to detect any association between the phenotypic sex of progeny and parental haplotypes. Offspring were reared in a common tank in outdoor conditions and sexed at the froglet stage. We could map a total of 2177 SNPs (1123 in the mother, 1054 in the father), recovering in both adults 13 linkage groups (= chromosome pairs) that were strongly syntenic to Xenopus tropicalis despite > 200 My divergence. Sexes differed strikingly in the localization of crossovers, which were uniformly distributed in the female but limited to chromosome ends in the male. None of the 2177 markers showed significant association with offspring sex. Considering the very high power of our analysis, we conclude that sex determination was not genetic in this family; which factors determined sex remain to be investigated.
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Affiliation(s)
- A Brelsford
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - N Rodrigues
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - N Perrin
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
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21
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Brelsford A, Dufresnes C, Perrin N. High-density sex-specific linkage maps of a European tree frog (Hyla arborea) identify the sex chromosome without information on offspring sex. Heredity (Edinb) 2015; 116:177-81. [PMID: 26374238 DOI: 10.1038/hdy.2015.83] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 06/12/2015] [Accepted: 07/29/2015] [Indexed: 01/16/2023] Open
Abstract
Identifying homology between sex chromosomes of different species is essential to understanding the evolution of sex determination. Here, we show that the identity of a homomorphic sex chromosome pair can be established using a linkage map, without information on offspring sex. By comparing sex-specific maps of the European tree frog Hyla arborea, we find that the sex chromosome (linkage group 1) shows a threefold difference in marker number between the male and female maps. In contrast, the number of markers on each autosome is similar between the two maps. We also find strongly conserved synteny between H. arborea and Xenopus tropicalis across 200 million years of evolution, suggesting that the rate of chromosomal rearrangement in anurans is low. Finally, we show that recombination in males is greatly reduced at the centers of large chromosomes, consistent with previous cytogenetic findings. Our research shows the importance of high-density linkage maps for studies of recombination, chromosomal rearrangement and the genetic architecture of ecologically or economically important traits.
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Affiliation(s)
- A Brelsford
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - C Dufresnes
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - N Perrin
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
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22
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Dufresnes C, Borzée A, Horn A, Stöck M, Ostini M, Sermier R, Wassef J, Litvinchuck SN, Kosch TA, Waldman B, Jang Y, Brelsford A, Perrin N. Sex-Chromosome Homomorphy in Palearctic Tree Frogs Results from Both Turnovers and X-Y Recombination. Mol Biol Evol 2015; 32:2328-37. [PMID: 25957317 DOI: 10.1093/molbev/msv113] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Contrasting with birds and mammals, poikilothermic vertebrates often have homomorphic sex chromosomes, possibly resulting from high rates of sex-chromosome turnovers and/or occasional X-Y recombination. Strong support for the latter mechanism was provided by four species of European tree frogs, which inherited from a common ancestor (∼ 5 Ma) the same pair of homomorphic sex chromosomes (linkage group 1, LG1), harboring the candidate sex-determining gene Dmrt1. Here, we test sex linkage of LG1 across six additional species of the Eurasian Hyla radiation with divergence times ranging from 6 to 40 Ma. LG1 turns out to be sex linked in six of nine resolved cases. Mapping the patterns of sex linkage to the Hyla phylogeny reveals several transitions in sex-determination systems within the last 10 My, including one switch in heterogamety. Phylogenetic trees of DNA sequences along LG1 are consistent with occasional X-Y recombination in all species where LG1 is sex linked. These patterns argue against one of the main potential causes for turnovers, namely the accumulation of deleterious mutations on nonrecombining chromosomes. Sibship analyses show that LG1 recombination is strongly reduced in males from most species investigated, including some in which it is autosomal. Intrinsically low male recombination might facilitate the evolution of male heterogamety, and the presence of important genes from the sex-determination cascade might predispose LG1 to become a sex chromosome.
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Affiliation(s)
- Christophe Dufresnes
- Department of Ecology & Evolution, Biophore Building, University of Lausanne, Lausanne, Switzerland
| | - Amaël Borzée
- Laboratory of Behavioral and Population Ecology, School of Biological Sciences, Seoul National University, Seoul, Republic of Korea
| | - Agnès Horn
- Department of Ecology & Evolution, Biophore Building, University of Lausanne, Lausanne, Switzerland
| | - Matthias Stöck
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries-IGB, Berlin, Germany
| | - Massimo Ostini
- Department of Ecology & Evolution, Biophore Building, University of Lausanne, Lausanne, Switzerland
| | - Roberto Sermier
- Department of Ecology & Evolution, Biophore Building, University of Lausanne, Lausanne, Switzerland
| | - Jérôme Wassef
- Department of Ecology & Evolution, Biophore Building, University of Lausanne, Lausanne, Switzerland
| | | | - Tiffany A Kosch
- Laboratory of Behavioral and Population Ecology, School of Biological Sciences, Seoul National University, Seoul, Republic of Korea
| | - Bruce Waldman
- Laboratory of Behavioral and Population Ecology, School of Biological Sciences, Seoul National University, Seoul, Republic of Korea
| | - Yikweon Jang
- Department of Life Sciences and Division of EcoScience, Ewha Womans University, Seoul, Republic of Korea
| | - Alan Brelsford
- Department of Ecology & Evolution, Biophore Building, University of Lausanne, Lausanne, Switzerland
| | - Nicolas Perrin
- Department of Ecology & Evolution, Biophore Building, University of Lausanne, Lausanne, Switzerland
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Tamschick S, Rozenblut-Kościsty B, Bonato L, Dufresnes C, Lymberakis P, Kloas W, Ogielska M, Stöck M. Sex Chromosome Conservation, DMRT1 Phylogeny and Gonad Morphology in Diploid Palearctic Green Toads ( Bufo viridis Subgroup). Cytogenet Genome Res 2015; 144:315-24. [DOI: 10.1159/000380841] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/26/2015] [Indexed: 11/19/2022] Open
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24
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Betto-Colliard C, Sermier R, Litvinchuk S, Perrin N, Stöck M. Origin and genome evolution of polyploid green toads in Central Asia: evidence from microsatellite markers. Heredity (Edinb) 2015; 114:300-8. [PMID: 25370211 PMCID: PMC4815583 DOI: 10.1038/hdy.2014.100] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 09/10/2014] [Accepted: 09/22/2014] [Indexed: 02/08/2023] Open
Abstract
Polyploidization, which is expected to trigger major genomic reorganizations, occurs much less commonly in animals than in plants, possibly because of constraints imposed by sex-determination systems. We investigated the origins and consequences of allopolyploidization in Palearctic green toads (Bufo viridis subgroup) from Central Asia, with three ploidy levels and different modes of genome transmission (sexual versus clonal), to (i) establish a topology for the reticulate phylogeny in a species-rich radiation involving several closely related lineages and (ii) explore processes of genomic reorganization that may follow polyploidization. Sibship analyses based on 30 cross-amplifying microsatellite markers substantiated the maternal origins and revealed the paternal origins and relationships of subgenomes in allopolyploids. Analyses of the synteny of linkage groups identified three markers affected by translocation events, which occurred only within the paternally inherited subgenomes of allopolyploid toads and exclusively affected the linkage group that determines sex in several diploid species of the green toad radiation. Recombination rates did not differ between diploid and polyploid toad species, and were overall much reduced in males, independent of linkage group and ploidy levels. Clonally transmitted subgenomes in allotriploid toads provided support for strong genetic drift, presumably resulting from recombination arrest. The Palearctic green toad radiation seems to offer unique opportunities to investigate the consequences of polyploidization and clonal transmission on the dynamics of genomes in vertebrates.
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Affiliation(s)
- C Betto-Colliard
- Department of Ecology and Evolution, Biophore Building University of Lausanne, Lausanne, Switzerland
| | - R Sermier
- Department of Ecology and Evolution, Biophore Building University of Lausanne, Lausanne, Switzerland
| | - S Litvinchuk
- Institute of Cytology, Russian Academy of Sciences, St Petersburg, Russia
| | - N Perrin
- Department of Ecology and Evolution, Biophore Building University of Lausanne, Lausanne, Switzerland
| | - M Stöck
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany
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25
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Dufresnes C, Brelsford A, Perrin N. First-generation linkage map for the European tree frog (Hyla arborea) with utility in congeneric species. BMC Res Notes 2014; 7:850. [PMID: 25430653 PMCID: PMC4258042 DOI: 10.1186/1756-0500-7-850] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 11/12/2014] [Indexed: 11/10/2022] Open
Abstract
Background Western Palearctic tree frogs (Hyla arborea group) represent a strong potential for evolutionary and conservation genetic research, so far underexploited due to limited molecular resources. New microsatellite markers have recently been developed for Hyla arborea, with high cross-species utility across the entire circum-Mediterranean radiation. Here we conduct sibship analyses to map available markers for use in future population genetic applications. Findings We characterized eight linkage groups, including one sex-linked, all showing drastically reduced recombination in males compared to females, as previously documented in this species. Mapping of the new 15 markers to the ~200 My diverged Xenopus tropicalis genome suggests a generally conserved synteny with only one confirmed major chromosome rearrangement. Conclusions The new microsatellites are representative of several chromosomes of H. arborea that are likely to be conserved across closely-related species. Our linkage map provides an important resource for genetic research in European Hylids, notably for studies of speciation, genome evolution and conservation. Electronic supplementary material The online version of this article (doi:10.1186/1756-0500-7-850) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Christophe Dufresnes
- Department of Ecology and Evolution, Biophore building, University of Lausanne, 1015 Lausanne, Switzerland.
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26
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Dufresnes C, Bertholet Y, Wassef J, Ghali K, Savary R, Pasteur B, Brelsford A, Rozenblut-Kościsty B, Ogielska M, Stöck M, Perrin N. Sex-chromosome differentiation parallels postglacial range expansion in European tree frogs (Hyla arborea). Evolution 2014; 68:3445-56. [PMID: 25209463 DOI: 10.1111/evo.12525] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 08/25/2014] [Indexed: 11/28/2022]
Abstract
Occasional XY recombination is a proposed explanation for the sex-chromosome homomorphy in European tree frogs. Numerous laboratory crosses, however, failed to detect any event of male recombination, and a detailed survey of NW-European Hyla arborea populations identified male-specific alleles at sex-linked loci, pointing to the absence of XY recombination in their recent history. Here, we address this paradox in a phylogeographic framework by genotyping sex-linked microsatellite markers in populations and sibships from the entire species range. Contrasting with postglacial populations of NW Europe, which display complete absence of XY recombination and strong sex-chromosome differentiation, refugial populations of the southern Balkans and Adriatic coast show limited XY recombination and large overlaps in allele frequencies. Geographically and historically intermediate populations of the Pannonian Basin show intermediate patterns of XY differentiation. Even in populations where X and Y occasionally recombine, the genetic diversity of Y haplotypes is reduced below the levels expected from the fourfold drop in copy numbers. This study is the first in which X and Y haplotypes could be phased over the distribution range in a species with homomorphic sex chromosomes; it shows that XY-recombination patterns may differ strikingly between conspecific populations, and that recombination arrest may evolve rapidly (<5000 generations).
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Affiliation(s)
- Christophe Dufresnes
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, 1015, Lausanne
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27
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Dufresnes C, Stöck M, Brelsford A, Perrin N. Range-wide sex-chromosome sequence similarity supports occasional XY recombination in European tree frogs (Hyla arborea). PLoS One 2014; 9:e97959. [PMID: 24892652 PMCID: PMC4043726 DOI: 10.1371/journal.pone.0097959] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 04/27/2014] [Indexed: 11/18/2022] Open
Abstract
In contrast with mammals and birds, most poikilothermic vertebrates feature structurally undifferentiated sex chromosomes, which may result either from frequent turnovers, or from occasional events of XY recombination. The latter mechanism was recently suggested to be responsible for sex-chromosome homomorphy in European tree frogs (Hyla arborea). However, no single case of male recombination has been identified in large-scale laboratory crosses, and populations from NW Europe consistently display sex-specific allelic frequencies with male-diagnostic alleles, suggesting the absence of recombination in their recent history. To address this apparent paradox, we extended the phylogeographic scope of investigations, by analyzing the sequences of three sex-linked markers throughout the whole species distribution. Refugial populations (southern Balkans and Adriatic coast) show a mix of X and Y alleles in haplotypic networks, and no more within-individual pairwise nucleotide differences in males than in females, testifying to recurrent XY recombination. In contrast, populations of NW Europe, which originated from a recent postglacial expansion, show a clear pattern of XY differentiation; the X and Y gametologs of the sex-linked gene Med15 present different alleles, likely fixed by drift on the front wave of expansions, and kept differentiated since. Our results support the view that sex-chromosome homomorphy in H. arborea is maintained by occasional or historical events of recombination; whether the frequency of these events indeed differs between populations remains to be clarified.
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Affiliation(s)
- Christophe Dufresnes
- Department of Ecology and evolution, Biophore Building, University of Lausanne, Lausanne, Switzerland
| | - Matthias Stöck
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany
- * E-mail:
| | - Alan Brelsford
- Department of Ecology and evolution, Biophore Building, University of Lausanne, Lausanne, Switzerland
| | - Nicolas Perrin
- Department of Ecology and evolution, Biophore Building, University of Lausanne, Lausanne, Switzerland
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28
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Dufresnes C, Brelsford A, Béziers P, Perrin N. Stronger transferability but lower variability in transcriptomic- than in anonymous microsatellites: evidence from Hylid frogs. Mol Ecol Resour 2014; 14:716-25. [PMID: 24345298 DOI: 10.1111/1755-0998.12215] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 12/03/2013] [Accepted: 12/11/2013] [Indexed: 11/28/2022]
Abstract
A simple way to quickly optimize microsatellites in nonmodel organisms is to reuse loci available in closely related taxa; however, this approach can be limited by the stochastic and low cross-amplification success experienced in some groups (e.g. amphibians). An efficient alternative is to develop loci from transcriptome sequences. Transcriptomic microsatellites have been found to vary in their levels of cross-species amplification and variability, but this has to date never been tested in amphibians. Here, we compare the patterns of cross-amplification and levels of polymorphism of 18 published anonymous microsatellites isolated from genomic DNA vs. 17 loci derived from a transcriptome, across nine species of tree frogs (Hyla arborea and Hyla cinerea group). We established a clear negative relationship between divergence time and amplification success, which was much steeper for anonymous than transcriptomic markers, with half-lives (time at which 50% of the markers still amplify) of 1.1 and 37 My, respectively. Transcriptomic markers are significantly less polymorphic than anonymous loci, but remain variable across diverged taxa. We conclude that the exploitation of amphibian transcriptomes for developing microsatellites seems an optimal approach for multispecies surveys (e.g. analyses of hybrid zones, comparative linkage mapping), whereas anonymous microsatellites may be more informative for fine-scale analyses of intraspecific variation. Moreover, our results confirm the pattern that microsatellite cross-amplification is greatly variable among amphibians and should be assessed independently within target lineages. Finally, we provide a bank of microsatellites for Palaearctic tree frogs (so far only available for H. arborea), which will be useful for conservation and evolutionary studies in this radiation.
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Affiliation(s)
- Christophe Dufresnes
- Department of Ecology & Evolution, University of Lausanne, Biophore Building, Lausanne , 1015, Switzerland
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29
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Jones DB, Jerry DR, Khatkar MS, Raadsma HW, Zenger KR. A high-density SNP genetic linkage map for the silver-lipped pearl oyster, Pinctada maxima: a valuable resource for gene localisation and marker-assisted selection. BMC Genomics 2013; 14:810. [PMID: 24252414 PMCID: PMC4046678 DOI: 10.1186/1471-2164-14-810] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 11/18/2013] [Indexed: 11/26/2022] Open
Abstract
Background The silver-lipped pearl oyster, Pinctada maxima, is an important tropical aquaculture species extensively farmed for the highly sought "South Sea" pearls. Traditional breeding programs have been initiated for this species in order to select for improved pearl quality, but many economic traits under selection are complex, polygenic and confounded with environmental factors, limiting the accuracy of selection. The incorporation of a marker-assisted selection (MAS) breeding approach would greatly benefit pearl breeding programs by allowing the direct selection of genes responsible for pearl quality. However, before MAS can be incorporated, substantial genomic resources such as genetic linkage maps need to be generated. The construction of a high-density genetic linkage map for P. maxima is not only essential for unravelling the genomic architecture of complex pearl quality traits, but also provides indispensable information on the genome structure of pearl oysters. Results A total of 1,189 informative genome-wide single nucleotide polymorphisms (SNPs) were incorporated into linkage map construction. The final linkage map consisted of 887 SNPs in 14 linkage groups, spans a total genetic distance of 831.7 centimorgans (cM), and covers an estimated 96% of the P. maxima genome. Assessment of sex-specific recombination across all linkage groups revealed limited overall heterochiasmy between the sexes (i.e. 1.15:1 F/M map length ratio). However, there were pronounced localised differences throughout the linkage groups, whereby male recombination was suppressed near the centromeres compared to female recombination, but inflated towards telomeric regions. Mean values of LD for adjacent SNP pairs suggest that a higher density of markers will be required for powerful genome-wide association studies. Finally, numerous nacre biomineralization genes were localised providing novel positional information for these genes. Conclusions This high-density SNP genetic map is the first comprehensive linkage map for any pearl oyster species. It provides an essential genomic tool facilitating studies investigating the genomic architecture of complex trait variation and identifying quantitative trait loci for economically important traits useful in genetic selection programs within the P. maxima pearling industry. Furthermore, this map provides a foundation for further research aiming to improve our understanding of the dynamic process of biomineralization, and pearl oyster evolution and synteny. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-14-810) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- David B Jones
- Centre for Sustainable Tropical Fisheries & Aquaculture, The School of Marine and Tropical Biology, James Cook University, Townsville, QLD, Australia.
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30
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Dufresnes C, Wassef J, Ghali K, Brelsford A, Stöck M, Lymberakis P, Crnobrnja-Isailovic J, Perrin N. Conservation phylogeography: does historical diversity contribute to regional vulnerability in European tree frogs (Hyla arborea)? Mol Ecol 2013; 22:5669-84. [PMID: 24102652 DOI: 10.1111/mec.12513] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 08/24/2013] [Accepted: 08/28/2013] [Indexed: 11/28/2022]
Abstract
Documenting and preserving the genetic diversity of populations, which conditions their long-term survival, have become a major issue in conservation biology. The loss of diversity often documented in declining populations is usually assumed to result from human disturbances; however, historical biogeographic events, otherwise known to strongly impact diversity, are rarely considered in this context. We apply a multilocus phylogeographic study to investigate the late-Quaternary history of a tree frog (Hyla arborea) with declining populations in the northern and western part of its distribution range. Mitochondrial and nuclear polymorphisms reveal high genetic diversity in the Balkan Peninsula, with a spatial structure moulded by the last glaciations. While two of the main refugial lineages remained limited to the Balkans (Adriatic coast, southern Balkans), a third one expanded to recolonize Northern and Western Europe, loosing much of its diversity in the process. Our findings show that mobile and a priori homogeneous taxa may also display substructure within glacial refugia ('refugia within refugia') and emphasize the importance of the Balkans as a major European biodiversity centre. Moreover, the distribution of diversity roughly coincides with regional conservation situations, consistent with the idea that historically impoverished genetic diversity may interact with anthropogenic disturbances, and increase the vulnerability of populations. Phylogeographic models seem important to fully appreciate the risks of local declines and inform conservation strategies.
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Affiliation(s)
- Christophe Dufresnes
- Department of Ecology & Evolution, University of Lausanne, Biophore Building, 1015, Lausanne, Switzerland
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31
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Stöck M, Savary R, Zaborowska A, Górecki G, Brelsford A, Rozenblut-Kościsty B, Ogielska M, Perrin N. Maintenance of ancestral sex chromosomes in Palearctic tree frogs: direct evidence from Hyla orientalis. Sex Dev 2013; 7:261-6. [PMID: 23735903 DOI: 10.1159/000351089] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/22/2013] [Indexed: 11/19/2022] Open
Abstract
Contrasting with the situation found in birds and mammals, sex chromosomes are generally homomorphic in poikilothermic vertebrates. This homomorphy was recently shown to result from occasional X-Y recombinations (not from turnovers) in several European species of tree frogs (Hyla arborea, H. intermedia and H. molleri). Because of recombination, however, alleles at sex-linked loci were rarely diagnostic at the population level; support for sex linkage had to rely on multilocus associations, combined with occasional sex differences in allelic frequencies. Here, we use direct evidence, obtained from anatomical and histological analyses of offspring with known pedigrees, to show that the Eastern tree frog (H. orientalis) shares the same pair of sex chromosomes, with identical patterns of male heterogamety and complete absence of X-Y recombination in males. Conservation of an ancestral pair of sex chromosomes, regularly rejuvenated via occasional X-Y recombination, seems thus a widespread pattern among Hyla species. Sibship analyses also identified discrepancies between genotypic and phenotypic sex among offspring, associated with abnormal gonadal development, suggesting a role for sexually antagonistic genes on the sex chromosomes.
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Affiliation(s)
- M Stöck
- Department of Ecology and Evolution, University of Lausanne, Switzerland
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32
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Brelsford A, Stöck M, Betto-Colliard C, Dubey S, Dufresnes C, Jourdan-Pineau H, Rodrigues N, Savary R, Sermier R, Perrin N. HOMOLOGOUS SEX CHROMOSOMES IN THREE DEEPLY DIVERGENT ANURAN SPECIES. Evolution 2013; 67:2434-40. [DOI: 10.1111/evo.12151] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 04/15/2013] [Indexed: 12/22/2022]
Affiliation(s)
- Alan Brelsford
- Department of Ecology and Evolution; University of Lausanne; 1015 Lausanne Switzerland
| | - Matthias Stöck
- Department of Ecology and Evolution; University of Lausanne; 1015 Lausanne Switzerland
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB); Müggelseedamm; 310, D-12587 Berlin Germany
| | | | - Sylvain Dubey
- Department of Ecology and Evolution; University of Lausanne; 1015 Lausanne Switzerland
| | - Christophe Dufresnes
- Department of Ecology and Evolution; University of Lausanne; 1015 Lausanne Switzerland
| | - Hélène Jourdan-Pineau
- Department of Ecology and Evolution; University of Lausanne; 1015 Lausanne Switzerland
| | - Nicolas Rodrigues
- Department of Ecology and Evolution; University of Lausanne; 1015 Lausanne Switzerland
| | - Romain Savary
- Department of Ecology and Evolution; University of Lausanne; 1015 Lausanne Switzerland
| | - Roberto Sermier
- Department of Ecology and Evolution; University of Lausanne; 1015 Lausanne Switzerland
| | - Nicolas Perrin
- Department of Ecology and Evolution; University of Lausanne; 1015 Lausanne Switzerland
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33
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Stöck M, Savary R, Betto-Colliard C, Biollay S, Jourdan-Pineau H, Perrin N. Low rates of X-Y recombination, not turnovers, account for homomorphic sex chromosomes in several diploid species of Palearctic green toads (Bufo viridis
subgroup). J Evol Biol 2013; 26:674-82. [DOI: 10.1111/jeb.12086] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 11/22/2012] [Accepted: 11/24/2012] [Indexed: 11/30/2022]
Affiliation(s)
- M. Stöck
- Department of Ecology and Evolution (DEE); University of Lausanne; Lausanne Switzerland
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB); Müggelseedamm 310 Berlin Germany
| | - R. Savary
- Department of Ecology and Evolution (DEE); University of Lausanne; Lausanne Switzerland
| | - C. Betto-Colliard
- Department of Ecology and Evolution (DEE); University of Lausanne; Lausanne Switzerland
| | - S. Biollay
- Department of Ecology and Evolution (DEE); University of Lausanne; Lausanne Switzerland
| | - H. Jourdan-Pineau
- Department of Ecology and Evolution (DEE); University of Lausanne; Lausanne Switzerland
| | - N. Perrin
- Department of Ecology and Evolution (DEE); University of Lausanne; Lausanne Switzerland
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34
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Within- and among-population impact of genetic erosion on adult fitness-related traits in the European tree frog Hyla arborea. Heredity (Edinb) 2012; 110:347-54. [PMID: 23250010 DOI: 10.1038/hdy.2012.110] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Assessing in wild populations how fitness is impacted by inbreeding and genetic drift is a major goal for conservation biology. An approach to measure the detrimental effects of inbreeding on fitness is to estimate correlations between molecular variation and phenotypic performances within and among populations. Our study investigated the effect of individual multilocus heterozygosity on body size, body condition and reproductive investment of males (that is, chorus attendance) and females (that is, clutch mass and egg size) in both small fragmented and large non-fragmented populations of European tree frog (Hyla arborea). Because adult size and/or condition and reproductive investment are usually related, genetic erosion may have detrimental effects directly on reproductive investment, and also on individual body size and condition that in turn may affect reproductive investment. We confirmed that the reproductive investment was highly size-dependent for both sexes. Larger females invested more in offspring production, and larger males attended the chorus in the pond more often. Our results did not provide evidence for a decline in body size, condition and reproductive effort with decreased multilocus heterozygosity both within and among populations. We showed that the lack of heterozygosity-fitness correlations within populations probably resulted from low inbreeding levels (inferior to ca. 20% full-sib mating rate), even in the small fragmented populations. The detrimental effects of fixation load were either low in adults or hidden by environmental variation among populations. These findings will be useful to design specific management actions to improve population persistence.
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35
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Guerrero RF, Kirkpatrick M, Perrin N. Cryptic recombination in the ever‐young sex chromosomes of
H
ylid frogs. J Evol Biol 2012; 25:1947-1954. [DOI: 10.1111/j.1420-9101.2012.02591.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2012] [Revised: 06/22/2012] [Accepted: 07/09/2012] [Indexed: 11/29/2022]
Affiliation(s)
- R. F. Guerrero
- Section of Integrative Biology The University of Texas at Austin Austin TX USA
| | - M. Kirkpatrick
- Section of Integrative Biology The University of Texas at Austin Austin TX USA
| | - N. Perrin
- Department of Ecology and Evolution University of Lausanne Lausanne Switzerland
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36
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PRUNIER J, KAUFMANN B, GROLET O, PICARD D, POMPANON F, JOLY P. Skin swabbing as a new efficient DNA sampling technique in amphibians, and 14 new microsatellite markers in the alpine newt (
Ichthyosaura alpestris
). Mol Ecol Resour 2012; 12:524-31. [DOI: 10.1111/j.1755-0998.2012.03116.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- J. PRUNIER
- Ecosphère, 3bis rue des Remises, 94100 Saint Maur des Fossés, France
- UMR5023 Ecologie des Hydrosystèmes Naturels et Anthropisés, Université de Lyon, Université Lyon 1, ENTPE, CNRS, Villeurbanne, F‐69622, France
| | - B. KAUFMANN
- UMR5023 Ecologie des Hydrosystèmes Naturels et Anthropisés, Université de Lyon, Université Lyon 1, ENTPE, CNRS, Villeurbanne, F‐69622, France
| | - O. GROLET
- UMR5023 Ecologie des Hydrosystèmes Naturels et Anthropisés, Université de Lyon, Université Lyon 1, ENTPE, CNRS, Villeurbanne, F‐69622, France
| | - D. PICARD
- Université d’Angers, Laboratoire d’Etudes Environnementales des Systèmes Anthropisés, 2 Boulevard Lavoisier, 49045 Angers Cedex 01, France
| | - F. POMPANON
- Université Joseph Fourier, Laboratoire d’Ecologie Alpine, CNRS, UMR 5553, 2233 Rue de la Piscine, 38041 Grenoble Cedex 9, France
| | - P. JOLY
- UMR5023 Ecologie des Hydrosystèmes Naturels et Anthropisés, Université de Lyon, Université Lyon 1, ENTPE, CNRS, Villeurbanne, F‐69622, France
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37
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Abstract
Although sex chromosomes have been the focus of a great deal of scientific scrutiny, most interest has centred on understanding the evolution and relative importance of X and Z chromosomes. By contrast, the sex-limited W and Y chromosomes have received far less attention, both because of their generally degenerate nature and the difficulty in studying non-recombining and often highly heterochromatic genomic regions. However, recent theory and empirical evidence suggest that the W and Y chromosomes play a far more important role in sex-specific fitness traits than would be expected based on their size alone, and this importance may explain the persistence of some Y and W chromosomes in the face of powerful degradative forces. In addition to their role in fertility and fecundity, the sex-limited nature of these genomic regions results in unique evolutionary forces acting on Y and W chromosomes, implicating them as potentially major contributors to sexual selection and speciation. Recent empirical studies have borne out these predictions and revealed that some W and Y chromosomes play a vital role in key sex-specific evolutionary processes.
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Affiliation(s)
- Judith E Mank
- Department of Zoology, Edward Grey Institute, University of Oxford, South Parks Road, Oxford, UK.
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38
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Cano JM, Li MH, Laurila A, Vilkki J, Merilä J. First-generation linkage map for the common frog Rana temporaria reveals sex-linkage group. Heredity (Edinb) 2011; 107:530-6. [PMID: 21587305 DOI: 10.1038/hdy.2011.39] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The common frog (Rana temporaria) has become a model species in the fields of ecology and evolutionary biology. However, lack of genomic resources has been limiting utility of this species for detailed evolutionary genetic studies. Using a set of 107 informative microsatellite markers genotyped in a large full-sib family (800 F1 offspring), we created the first linkage map for this species. This partial map-distributed over 15 linkage groups-has a total length of 1698.8 cM. In line with the fact that males are the heterogametic sex in this species and a reduction of recombination is expected, we observed a lower recombination rate in the males (map length: 1371.5 cM) as compared with females (2089.8 cM). Furthermore, three loci previously documented to be sex-linked (that is, carrying male-specific alleles) in adults from the wild mapped to the same linkage group. The linkage map described in this study is one of the densest ones available for amphibians. The discovery of a sex linkage group in Rana temporaria, as well as other regions with strongly reduced male recombination rates, should help to uncover the genetic underpinnings of the sex-determination system in this species. As the number of linkage groups found (n=15) is quite close to the actual number of chromosomes (n=13), the map should provide a useful resource for further evolutionary, ecological and conservation genetic work in this and other closely related species.
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Affiliation(s)
- J M Cano
- Ecological Genetics Research Unit, Department of Biosciences, University of Helsinki, Helsinki, Finland.
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39
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Stöck M, Horn A, Grossen C, Lindtke D, Sermier R, Betto-Colliard C, Dufresnes C, Bonjour E, Dumas Z, Luquet E, Maddalena T, Sousa HC, Martinez-Solano I, Perrin N. Ever-young sex chromosomes in European tree frogs. PLoS Biol 2011; 9:e1001062. [PMID: 21629756 PMCID: PMC3100596 DOI: 10.1371/journal.pbio.1001062] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 04/06/2011] [Indexed: 11/23/2022] Open
Abstract
Non-recombining sex chromosomes are expected to undergo evolutionary decay,
ending up genetically degenerated, as has happened in birds and mammals. Why are
then sex chromosomes so often homomorphic in cold-blooded vertebrates? One
possible explanation is a high rate of turnover events, replacing master
sex-determining genes by new ones on other chromosomes. An alternative is that
X-Y similarity is maintained by occasional recombination events, occurring in
sex-reversed XY females. Based on mitochondrial and nuclear gene sequences, we
estimated the divergence times between European tree frogs (Hyla
arborea, H. intermedia, and H.
molleri) to the upper Miocene, about 5.4–7.1 million years
ago. Sibship analyses of microsatellite polymorphisms revealed that all three
species have the same pair of sex chromosomes, with complete absence of X-Y
recombination in males. Despite this, sequences of sex-linked loci show no
divergence between the X and Y chromosomes. In the phylogeny, the X and Y
alleles cluster according to species, not in groups of gametologs. We conclude
that sex-chromosome homomorphy in these tree frogs does not result from a recent
turnover but is maintained over evolutionary timescales by occasional X-Y
recombination. Seemingly young sex chromosomes may thus carry old-established
sex-determining genes, a result at odds with the view that sex chromosomes
necessarily decay until they are replaced. This raises intriguing perspectives
regarding the evolutionary dynamics of sexually antagonistic genes and the
mechanisms that control X-Y recombination. Non-recombining sex chromosomes, such as the Y chromosome, are expected to
degenerate over evolutionary times because they accumulate deleterious mutations
that cannot be corrected by recombination with a pristine copy. In most
cold-blooded vertebrates, such as frogs, however, sex chromosomes are
undifferentiated. Why is that so? On the one hand, the
“high-turnover” hypothesis holds that these sex chromosomes are
regularly replaced before they had time to decay. On the other hand, the
“fountain-of-youth” hypothesis posits that they are regularly
rejuvenated by X-Y recombination in sex-reversed XY females. Here, we show that
three species of tree frogs that diverged more than 5.4 million years ago share
the same pair of undifferentiated sex chromosomes. Although male recombination
stopped before species divergence, X and Y alleles show no differentiation, and
cluster by species, not gametologs. We conclude that their sex chromosome
homomorphy is not due to a recent turnover but is maintained over long
evolutionary times by occasional recombination. Such rare episodes of X-Y
recombination are expected to have long-lasting consequences on the evolution of
sex chromosomes and sex antagonistic genes.
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Affiliation(s)
- Matthias Stöck
- Department of Ecology and Evolution, University of Lausanne, Lausanne,
Switzerland
| | - Agnès Horn
- Department of Ecology and Evolution, University of Lausanne, Lausanne,
Switzerland
| | - Christine Grossen
- Department of Ecology and Evolution, University of Lausanne, Lausanne,
Switzerland
| | - Dorothea Lindtke
- Department of Ecology and Evolution, University of Lausanne, Lausanne,
Switzerland
- Department of Biology, University of Fribourg, Fribourg,
Switzerland
| | - Roberto Sermier
- Department of Ecology and Evolution, University of Lausanne, Lausanne,
Switzerland
| | | | - Christophe Dufresnes
- Department of Ecology and Evolution, University of Lausanne, Lausanne,
Switzerland
| | - Emmanuel Bonjour
- Department of Ecology and Evolution, University of Lausanne, Lausanne,
Switzerland
| | - Zoé Dumas
- Department of Ecology and Evolution, University of Lausanne, Lausanne,
Switzerland
- Umweltmikrobiologie, EAWAG, Dübendorf, Switzerland
| | - Emilien Luquet
- UMR 5023 Ecology of Fluvial Hydrosystems, Bât. Darwin C,
Université Lyon, Villeurbanne, France
| | | | - Helena Clavero Sousa
- Department of Ecology and Evolution, University of Lausanne, Lausanne,
Switzerland
- Perpetuo Socorro, Puerto Santa María (Cádiz),
Spain
| | - Iñigo Martinez-Solano
- Instituto de Investigación en Recursos Cinegéticos
(UCLM-CSIC-JCCM), Ciudad Real, Spain
| | - Nicolas Perrin
- Department of Ecology and Evolution, University of Lausanne, Lausanne,
Switzerland
- * E-mail:
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40
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Matsuba C, Alho JS, Merilä J. Recombination rate between sex chromosomes depends on phenotypic sex in the common frog. Evolution 2011; 64:3634-7. [PMID: 20624177 DOI: 10.1111/j.1558-5646.2010.01076.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We show that the recombination rate between the sex chromosomes is controlled by phenotypic, rather than genotypic, sex in sex-reversed common frogs. This supports the recent hypothesis that in ectothermic vertebrates sex reversal can prevent the progressive accumulation of mutations to nonrecombining Y chromosomes and their subsequent evolutionary decay.
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Affiliation(s)
- Chikako Matsuba
- Ecological Genetics Research Unit, Department of Biosciences, PO Box 65, FI-00014, University of Helsinki, Finland.
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41
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Luquet E, David P, Lena JP, Joly P, Konecny L, Dufresnes C, Perrin N, Plenet S. Heterozygosity-fitness correlations among wild populations of European tree frog (Hyla arborea) detect fixation load. Mol Ecol 2011; 20:1877-87. [PMID: 21410805 DOI: 10.1111/j.1365-294x.2011.05061.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Quantifying the impacts of inbreeding and genetic drift on fitness traits in fragmented populations is becoming a major goal in conservation biology. Such impacts occur at different levels and involve different sets of loci. Genetic drift randomly fixes slightly deleterious alleles leading to different fixation load among populations. By contrast, inbreeding depression arises from highly deleterious alleles in segregation within a population and creates variation among individuals. A popular approach is to measure correlations between molecular variation and phenotypic performances. This approach has been mainly used at the individual level to detect inbreeding depression within populations and sometimes at the population level but without consideration about the genetic processes measured. For the first time, we used in this study a molecular approach considering both the interpopulation and intrapopulation level to discriminate the relative importance of inbreeding depression vs. fixation load in isolated and non-fragmented populations of European tree frog (Hyla arborea), complemented with interpopulational crosses. We demonstrated that the positive correlations observed between genetic heterozygosity and larval performances on merged data were mainly caused by co-variations in genetic diversity and fixation load among populations rather than by inbreeding depression and segregating deleterious alleles within populations. Such a method is highly relevant in a conservation perspective because, depending on how populations lose fitness (inbreeding vs. fixation load), specific management actions may be designed to improve the persistence of populations.
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Affiliation(s)
- E Luquet
- Université Lyon 1, CNRS UMR 5023 Ecologie des Hydrosystèmes Fluviaux, Université Claude Bernard Lyon 1, Université de Lyon, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne Cedex, France.
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42
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STÖCK M, CROLL D, DUMAS Z, BIOLLAY S, WANG J, PERRIN N. A cryptic heterogametic transition revealed by sex-linked DNA markers in Palearctic green toads. J Evol Biol 2011; 24:1064-70. [DOI: 10.1111/j.1420-9101.2011.02239.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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43
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Broquet T, Angelone S, Jaquiery J, Joly P, Lena JP, Lengagne T, Plenet S, Luquet E, Perrin N. Genetic bottlenecks driven by population disconnection. CONSERVATION BIOLOGY : THE JOURNAL OF THE SOCIETY FOR CONSERVATION BIOLOGY 2010; 24:1596-1605. [PMID: 20666803 DOI: 10.1111/j.1523-1739.2010.01556.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Connectivity among populations plays a crucial role in maintaining genetic variation at a local scale, especially in small populations affected strongly by genetic drift. The negative consequences of population disconnection on allelic richness and gene diversity (heterozygosity) are well recognized and empirically established. It is not well recognized, however, that a sudden drop in local effective population size induced by such disconnection produces a temporary disequilibrium in allelic frequency distributions that is akin to the genetic signature of a demographic bottleneck. To document this effect, we used individual-based simulations and empirical data on allelic richness and gene diversity in six pairs of isolated versus well-connected (core) populations of European tree frogs. In our simulations, population disconnection depressed allelic richness more than heterozygosity and thus resulted in a temporary excess in gene diversity relative to mutation drift equilibrium (i.e., signature of a genetic bottleneck). We observed a similar excess in gene diversity in isolated populations of tree frogs. Our results show that population disconnection can create a genetic bottleneck in the absence of demographic collapse.
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Affiliation(s)
- Thomas Broquet
- Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland.
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44
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Charlesworth D, Mank JE. The birds and the bees and the flowers and the trees: lessons from genetic mapping of sex determination in plants and animals. Genetics 2010; 186:9-31. [PMID: 20855574 PMCID: PMC2940314 DOI: 10.1534/genetics.110.117697] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The ability to identify genetic markers in nonmodel systems has allowed geneticists to construct linkage maps for a diversity of species, and the sex-determining locus is often among the first to be mapped. Sex determination is an important area of study in developmental and evolutionary biology, as well as ecology. Its importance for organisms might suggest that sex determination is highly conserved. However, genetic studies have shown that sex determination mechanisms, and the genes involved, are surprisingly labile. We review studies using genetic mapping and phylogenetic inferences, which can help reveal evolutionary pattern within this lability and potentially identify the changes that have occurred among different sex determination systems. We define some of the terminology, particularly where confusion arises in writing about such a diverse range of organisms, and highlight some major differences between plants and animals, and some important similarities. We stress the importance of studying taxa suitable for testing hypotheses, and the need for phylogenetic studies directed to taxa where the patterns of changes can be most reliably inferred, if the ultimate goal of testing hypotheses regarding the selective forces that have led to changes in such an essential trait is to become feasible.
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Affiliation(s)
- Deborah Charlesworth
- Department of Zoology, Edward Grey Institute, University of Oxford, Oxford OX1 3PS, United Kingdom.
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45
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Wedekind C. Searching for sex-reversals to explain population demography and the evolution of sex chromosomes. Mol Ecol 2010; 19:1760-2. [PMID: 20529067 DOI: 10.1111/j.1365-294x.2010.04608.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Sex determination can be purely genetic (as in mammals and birds), purely environmental (as in many reptiles), or genetic but reversible by environmental factors during a sensitive period in life, as in many fish and amphibians (Wallace et al. 1999; Baroiller et al. 2009a; Stelkens & Wedekind 2010). Such environmental sex reversal (ESR) can be induced, for example, by temperature changes or by exposure to hormone-active substances. ESR has long been recognized as a means to produce more profitable single-sex cultures in fish farms (Cnaani & Levavi-Sivan 2009), but we know very little about its prevalence in the wild. Obviously, induced feminization or masculinization may immediately distort population sex ratios, and distorted sex ratios are indeed reported from some amphibian and fish populations (Olsen et al. 2006; Alho et al. 2008; Brykov et al. 2008). However, sex ratios can also be skewed by, for example, segregation distorters or sex-specific mortality. Demonstrating ESR in the wild therefore requires the identification of sex-linked genetic markers (in the absence of heteromorphic sex chromosomes) followed by comparison of genotypes and phenotypes, or experimental crosses with individuals who seem sex reversed, followed by sexing of offspring after rearing under non-ESR conditions and at low mortality. In this issue, Alho et al. (2010) investigate the role of ESR in the common frog (Rana temporaria) and a population that has a distorted adult sex ratio. They developed new sex-linked microsatellite markers and tested wild-caught male and female adults for potential mismatches between phenotype and genotype. They found a significant proportion of phenotypic males with a female genotype. This suggests environmental masculinization, here with a prevalence of 9%. The authors then tested whether XX males naturally reproduce with XX females. They collected egg clutches and found that some had indeed a primary sex ratio of 100% daughters. Other clutches seemed to result from multi-male fertilizations of which at least one male had the female genotype. These results suggest that sex-reversed individuals affect the sex ratio in the following generation. But how relevant is ESR if its prevalence is rather low, and what are the implications of successful reproduction of sex-reversed individuals in the wild?
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Affiliation(s)
- Claus Wedekind
- Department of Ecology and Evolution, Biophore, University of Lausanne, CH-1015 Lausanne, Switzerland.
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ALHO JUSSIS, MATSUBA CHIKAKO, MERILÄ JUHA. Sex reversal and primary sex ratios in the common frog (Rana temporaria). Mol Ecol 2010; 19:1763-73. [DOI: 10.1111/j.1365-294x.2010.04607.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Broquet T, Jaquiéry J, Perrin N. Opportunity for sexual selection and effective population size in the lek-breeding European treefrog (Hyla arborea). Evolution 2009; 63:674-83. [PMID: 19087183 DOI: 10.1111/j.1558-5646.2008.00586.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Sexual selection in lek-breeding species might drastically lower male effective population size, with potentially important consequences for evolutionary and conservation biology. Using field-monitoring and parental-assignment methods, we analyzed sex-specific variances in breeding success in a population of European treefrogs, to (1) help understanding the dynamics of genetic variance at sex-specific loci, and (2) better quantify the risk posed by genetic drift in this species locally endangered by habitat fragmentation. The variance in male mating success turned out to be markedly lower than values obtained from other amphibian species with polygamous mating systems. The ratio of effective breeding size to census breeding size was only slightly lower in males (0.44) than in females (0.57), in line with the patterns of genetic diversity previously reported from H. arborea sex chromosomes. Combining our results with data on age at maturity and adult survival, we show that the negative effect of the mating system is furthermore compensated by the effect of delayed maturity, so that the estimated instantaneous effective size broadly corresponded to census breeding size. We conclude that the lek-breeding system of treefrogs impacts only weakly the patterns of genetic diversity on sex-linked genes and the ability of natural populations to resist genetic drift.
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Affiliation(s)
- Thomas Broquet
- Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland.
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