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Wilhoit KT, Alexander EP, Blackmon H. Worse than nothing at all: the inequality of fusions joining autosomes to the PAR and non-PAR portions of sex chromosomes. PeerJ 2024; 12:e17740. [PMID: 39071118 PMCID: PMC11276758 DOI: 10.7717/peerj.17740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Accepted: 06/24/2024] [Indexed: 07/30/2024] Open
Abstract
Chromosomal fusions play an integral role in genome remodeling and karyotype evolution. Fusions that join a sex chromosome to an autosome are particularly abundant across the tree of life. However, previous models on the establishment of such fusions have not accounted for the physical structure of the chromosomes. We predict a fusion joining an autosome to the pseudoautosomal region (PAR) of a sex chromosome will not remain stable, and the fusion will switch from the X to the Y chromosome each generation due to recombination. We have produced a forward-time population genetic simulation to explore the outcomes of fusions to both the PAR and non-PAR of sex chromosomes. The model can simulate the fusion of an autosome containing a sexually antagonistic locus to either the PAR or non-PAR end of a sex chromosome. Our model is diploid, two-locus, and biallelic. Our results show a clear pattern where fusions to the non-PAR are favored in the presence of sexual antagonism, whereas fusions to the PAR are disfavored in the presence of sexual antagonism.
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Affiliation(s)
- Kayla T. Wilhoit
- Biomedical Sciences Program, Texas A&M University, College Station, TX, United States of America
- Department of Biology, Texas A&M University, College Station, TX, United States of America
- University Program in Genetics and Genomics, Duke University, Durham, NC, United States of America
| | - Emmarie P. Alexander
- Interdisciplinary Program in Genetics and Genomics, Texas A&M University, College Station, TX, United States of America
- Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, United States of America
| | - Heath Blackmon
- Department of Biology, Texas A&M University, College Station, TX, United States of America
- Interdisciplinary Program in Genetics and Genomics, Texas A&M University, College Station, TX, United States of America
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2
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Souza FHS, Perez MF, Ferreira PHN, Bertollo LAC, Ezaz T, Charlesworth D, Cioffi MB. Multiple karyotype differences between populations of the Hoplias malabaricus (Teleostei; Characiformes), a species complex in the gray area of the speciation process. Heredity (Edinb) 2024:10.1038/s41437-024-00707-z. [PMID: 39039117 DOI: 10.1038/s41437-024-00707-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 07/15/2024] [Accepted: 07/16/2024] [Indexed: 07/24/2024] Open
Abstract
Neotropical fishes exhibit remarkable karyotype diversity, whose evolution is poorly understood. Here, we studied genetic differences in 60 individuals, from 11 localities of one species, the wolf fish Hoplias malabaricus, from populations that include six different "karyomorphs". These differ in Y-X chromosome differentiation, and, in several cases, by fusions with autosomes that have resulted in multiple sex chromosomes. Other differences are also observed in diploid chromosome numbers and morphologies. In an attempt to start understanding how this diversity was generated, we analyzed within- and between-population differences in a genome-wide sequence data set. We detect clear genotype differences between karyomorphs. Even in sympatry, samples with different karyomorphs differ more in sequence than samples from allopatric populations of the same karyomorph, suggesting that they represent populations that are to some degree reproductively isolated. However, sequence divergence between populations with different karyomorphs is remarkably low, suggesting that chromosome rearrangements may have evolved during a brief evolutionary time. We suggest that the karyotypic differences probably evolved in allopatry, in small populations that would have allowed rapid fixation of rearrangements, and that they became sympatric after their differentiation. Further studies are needed to test whether the karyotype differences contribute to reproductive isolation detected between some H. malabaricus karyomorphs.
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Affiliation(s)
- Fernando H S Souza
- Laboratory of Evolutionary Cytogenetics, Department of Genetics and Evolution, Federal University of São Carlos, São Carlos, SP, Brazil
| | - Manolo F Perez
- Laboratory of Evolutionary Cytogenetics, Department of Genetics and Evolution, Federal University of São Carlos, São Carlos, SP, Brazil
| | - Pedro H N Ferreira
- Laboratory of Evolutionary Cytogenetics, Department of Genetics and Evolution, Federal University of São Carlos, São Carlos, SP, Brazil
| | - Luiz A C Bertollo
- Laboratory of Evolutionary Cytogenetics, Department of Genetics and Evolution, Federal University of São Carlos, São Carlos, SP, Brazil
| | - Tariq Ezaz
- Institute for Applied Ecology, University of Canberra, Canberra, NSW, Australia
| | - Deborah Charlesworth
- Institute for Evolutionary Biology, Ashworth Laboratories, King's Buildings, University of Edinburgh, Edinburgh, UK
| | - Marcelo B Cioffi
- Laboratory of Evolutionary Cytogenetics, Department of Genetics and Evolution, Federal University of São Carlos, São Carlos, SP, Brazil.
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Chase MA, Vilcot M, Mugal CF. The role of recombination dynamics in shaping signatures of direct and indirect selection across the Ficedula flycatcher genome †. Proc Biol Sci 2024; 291:20232382. [PMID: 38228173 DOI: 10.1098/rspb.2023.2382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 12/14/2023] [Indexed: 01/18/2024] Open
Abstract
Recombination is a central evolutionary process that reshuffles combinations of alleles along chromosomes, and consequently is expected to influence the efficacy of direct selection via Hill-Robertson interference. Additionally, the indirect effects of selection on neutral genetic diversity are expected to show a negative relationship with recombination rate, as background selection and genetic hitchhiking are stronger when recombination rate is low. However, owing to the limited availability of recombination rate estimates across divergent species, the impact of evolutionary changes in recombination rate on genomic signatures of selection remains largely unexplored. To address this question, we estimate recombination rate in two Ficedula flycatcher species, the taiga flycatcher (Ficedula albicilla) and collared flycatcher (Ficedula albicollis). We show that recombination rate is strongly correlated with signatures of indirect selection, and that evolutionary changes in recombination rate between species have observable impacts on this relationship. Conversely, signatures of direct selection on coding sequences show little to no relationship with recombination rate, even when restricted to genes where recombination rate is conserved between species. Thus, using measures of indirect and direct selection that bridge micro- and macro-evolutionary timescales, we demonstrate that the role of recombination rate and its dynamics varies for different signatures of selection.
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Affiliation(s)
- Madeline A Chase
- Department of Ecology and Genetics, Uppsala University, 75236 Uppsala, Sweden
- Swiss Ornithological Institute, 6204 Sempach, Switzerland
| | - Maurine Vilcot
- Department of Ecology and Genetics, Uppsala University, 75236 Uppsala, Sweden
- CEFE, University of Montpellier, CNRS, EPHE, IRD, 34293 Montpellier 5, France
| | - Carina F Mugal
- Department of Ecology and Genetics, Uppsala University, 75236 Uppsala, Sweden
- Laboratory of Biometry and Evolutionary Biology, University of Lyon 1, CNRS UMR 5558, 69622 Villeurbanne cedex, France
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4
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Zhang H, Lundberg M, Tarka M, Hasselquist D, Hansson B. Evidence of Site-Specific and Male-Biased Germline Mutation Rate in a Wild Songbird. Genome Biol Evol 2023; 15:evad180. [PMID: 37793164 PMCID: PMC10627410 DOI: 10.1093/gbe/evad180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 09/07/2023] [Accepted: 09/26/2023] [Indexed: 10/06/2023] Open
Abstract
Germline mutations are the ultimate source of genetic variation and the raw material for organismal evolution. Despite their significance, the frequency and genomic locations of mutations, as well as potential sex bias, are yet to be widely investigated in most species. To address these gaps, we conducted whole-genome sequencing of 12 great reed warblers (Acrocephalus arundinaceus) in a pedigree spanning 3 generations to identify single-nucleotide de novo mutations (DNMs) and estimate the germline mutation rate. We detected 82 DNMs within the pedigree, primarily enriched at CpG sites but otherwise randomly located along the chromosomes. Furthermore, we observed a pronounced sex bias in DNM occurrence, with male warblers exhibiting three times more mutations than females. After correction for false negatives and adjusting for callable sites, we obtained a mutation rate of 7.16 × 10-9 mutations per site per generation (m/s/g) for the autosomes and 5.10 × 10-9 m/s/g for the Z chromosome. To demonstrate the utility of species-specific mutation rates, we applied our autosomal mutation rate in models reconstructing the demographic history of the great reed warbler. We uncovered signs of drastic population size reductions predating the last glacial period (LGP) and reduced gene flow between western and eastern populations during the LGP. In conclusion, our results provide one of the few direct estimates of the mutation rate in wild songbirds and evidence for male-driven mutations in accordance with theoretical expectations.
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Affiliation(s)
- Hongkai Zhang
- Department of Biology, Lund University, Lund, Sweden
| | - Max Lundberg
- Department of Biology, Lund University, Lund, Sweden
| | - Maja Tarka
- Department of Biology, Lund University, Lund, Sweden
| | | | - Bengt Hansson
- Department of Biology, Lund University, Lund, Sweden
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Burley JT, Orzechowski SCM, Sin SYW, Edwards SV. Whole-genome phylogeography of the blue-faced honeyeater (Entomyzon cyanotis) and discovery and characterization of a neo-Z chromosome. Mol Ecol 2023; 32:1248-1270. [PMID: 35797346 DOI: 10.1111/mec.16604] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 06/22/2022] [Accepted: 07/04/2022] [Indexed: 11/28/2022]
Abstract
Whole-genome surveys of genetic diversity and geographic variation often yield unexpected discoveries of novel structural variation, which long-read DNA sequencing can help clarify. Here, we report on whole-genome phylogeography of a bird exhibiting classic vicariant geographies across Australia and New Guinea, the blue-faced honeyeater (Entomyzon cyanotis), and the discovery and characterization of a novel neo-Z chromosome by long-read sequencing. Using short-read genome-wide SNPs, we inferred population divergence events within E. cyanotis across the Carpentarian and other biogeographic barriers during the Pleistocene (~0.3-1.7 Ma). Evidence for introgression between nonsister populations supports a hypothesis of reticulate evolution around a triad of dynamic barriers around Pleistocene Lake Carpentaria between Australia and New Guinea. During this phylogeographic survey, we discovered a large (134 Mbp) neo-Z chromosome and we explored its diversity, divergence and introgression landscape. We show that, as in some sylvioid passerine birds, a fusion occurred between chromosome 5 and the Z chromosome to form a neo-Z chromosome; and in E. cyanotis, the ancestral pseudoautosomal region (PAR) appears nonrecombinant between Z and W, along with most of the fused chromosome 5. The added recombination-suppressed portion of the neo-Z (~37.2 Mbp) displays reduced diversity and faster population genetic differentiation compared with the ancestral-Z. Yet, the new PAR (~17.4 Mbp) shows elevated diversity and reduced differentiation compared to autosomes, potentially resulting from introgression. In our case, long-read sequencing helped clarify the genomic landscape of population divergence on autosomes and sex chromosomes in a species where prior knowledge of genome structure was still incomplete.
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Affiliation(s)
- John T Burley
- Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, USA.,Department of Evolutionary Biology, Evolutionary Biology Centre (EBC), Uppsala University, Uppsala, Sweden.,Department of Ecology Evolution and Organismal Biology, Brown University, Providence, Rhode Island, USA.,Institute at Brown for Environment and Society, Brown University, Providence, Rhode Island, USA
| | | | - Simon Yung Wa Sin
- Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, USA.,School of Biological Sciences, The University of Hong Kong, Hong Kong SAR, China
| | - Scott V Edwards
- Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, USA
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Sigeman H, Zhang H, Ali Abed S, Hansson B. A novel neo-sex chromosome in Sylvietta brachyura (Macrosphenidae) adds to the extraordinary avian sex chromosome diversity among Sylvioidea songbirds. J Evol Biol 2022; 35:1797-1805. [PMID: 36156325 PMCID: PMC10087220 DOI: 10.1111/jeb.14096] [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: 01/26/2022] [Revised: 06/03/2022] [Accepted: 07/21/2022] [Indexed: 11/29/2022]
Abstract
We report the discovery of a novel neo-sex chromosome in an African warbler, Sylvietta brachyura (northern crombec; Macrosphenidae). This species is part of the Sylvioidea superfamily, where four separate autosome-sex chromosome translocation events have previously been discovered via comparative genomics of 11 of the 22 families in this clade. Our discovery here resulted from analyses of genomic data of single species-representatives from three additional Sylvioidea families (Macrosphenidae, Pycnonotidae and Leiothrichidae). In all three species, we confirmed the translocation of a part of chromosome 4A to the sex chromosomes, which originated basally in Sylvioidea. In S. brachyura, we found that a part of chromosome 8 has been translocated to the sex chromosomes, forming a unique neo-sex chromosome in this lineage. Furthermore, the non-recombining part of 4A in S. brachyura is smaller than in other Sylvioidea species, which suggests that recombination continued along this region after the fusion event in the Sylvioidea ancestor. These findings reveal additional sex chromosome diversity among the Sylvioidea, where five separate translocation events are now confirmed.
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Affiliation(s)
- Hanna Sigeman
- Department of Biology, Lund University, Lund, Sweden.,Ecology and Genetics Research Unit, University of Oulu, Oulu, Finland
| | - Hongkai Zhang
- Department of Biology, Lund University, Lund, Sweden
| | | | - Bengt Hansson
- Department of Biology, Lund University, Lund, Sweden
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Zhang H, Sigeman H, Hansson B. Assessment of phylogenetic approaches to study the timing of recombination cessation on sex chromosomes. J Evol Biol 2022; 35:1721-1733. [PMID: 35895083 PMCID: PMC10086819 DOI: 10.1111/jeb.14068] [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: 01/28/2022] [Revised: 06/18/2022] [Accepted: 06/26/2022] [Indexed: 12/01/2022]
Abstract
The evolution of sex chromosomes is hypothesized to be punctuated by consecutive recombination cessation events, forming "evolutionary strata" that ceased to recombine at different time points. The demarcation of evolutionary strata is often assessed by estimates of the timing of recombination cessation (tRC ) along the sex chromosomes, commonly inferred from the level of synonymous divergence or with species phylogenies at gametologous (X-Y or Z-W) sequence data. However, drift and selection affect sequences unpredictably and introduce uncertainty when inferring tRC . Here, we assess two alternative phylogenetic approaches to estimate tRC ; (i) the expected likelihood weight (ELW) approach that finds the most likely topology among a set of hypothetical topologies and (ii) the BEAST approach that estimates tRC with specified calibration priors on a reference species topology. By using Z and W gametologs of an old and a young evolutionary stratum on the neo-sex chromosome of Sylvioidea songbirds, we show that the ELW and BEAST approaches yield similar tRC estimates, and that both outperform two frequently applied approaches utilizing synonymous substitution rates (dS) and maximum likelihood (ML) trees, respectively. Moreover, we demonstrate that both ELW and BEAST provide more precise tRC estimates when sequences of multiple species are included in the analyses.
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Affiliation(s)
- Hongkai Zhang
- Department of Biology, Lund University, Lund, Sweden
| | - Hanna Sigeman
- Department of Biology, Lund University, Lund, Sweden
| | - Bengt Hansson
- Department of Biology, Lund University, Lund, Sweden
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