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Palahí I Torres A, Höök L, Näsvall K, Shipilina D, Wiklund C, Vila R, Pruisscher P, Backström N. The fine-scale recombination rate variation and associations with genomic features in a butterfly. Genome Res 2023; 33:810-823. [PMID: 37308293 PMCID: PMC10317125 DOI: 10.1101/gr.277414.122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 05/03/2023] [Indexed: 06/14/2023]
Abstract
Recombination is a key molecular mechanism that has profound implications on both micro- and macroevolutionary processes. However, the determinants of recombination rate variation in holocentric organisms are poorly understood, in particular in Lepidoptera (moths and butterflies). The wood white butterfly (Leptidea sinapis) shows considerable intraspecific variation in chromosome numbers and is a suitable system for studying regional recombination rate variation and its potential molecular underpinnings. Here, we developed a large whole-genome resequencing data set from a population of wood whites to obtain high-resolution recombination maps using linkage disequilibrium information. The analyses revealed that larger chromosomes had a bimodal recombination landscape, potentially caused by interference between simultaneous chiasmata. The recombination rate was significantly lower in subtelomeric regions, with exceptions associated with segregating chromosome rearrangements, showing that fissions and fusions can have considerable effects on the recombination landscape. There was no association between the inferred recombination rate and base composition, supporting a limited influence of GC-biased gene conversion in butterflies. We found significant but variable associations between the recombination rate and the density of different classes of transposable elements, most notably a significant enrichment of short interspersed nucleotide elements in genomic regions with higher recombination rate. Finally, the analyses unveiled significant enrichment of genes involved in farnesyltranstransferase activity in recombination coldspots, potentially indicating that expression of transferases can inhibit formation of chiasmata during meiotic division. Our results provide novel information about recombination rate variation in holocentric organisms and have particular implications for forthcoming research in population genetics, molecular/genome evolution, and speciation.
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Affiliation(s)
- Aleix Palahí I Torres
- Evolutionary Biology Program, Department of Ecology and Genetics (IEG), Uppsala University, SE-752 36 Uppsala, Sweden;
| | - Lars Höök
- Evolutionary Biology Program, Department of Ecology and Genetics (IEG), Uppsala University, SE-752 36 Uppsala, Sweden
| | - Karin Näsvall
- Evolutionary Biology Program, Department of Ecology and Genetics (IEG), Uppsala University, SE-752 36 Uppsala, Sweden
| | - Daria Shipilina
- Evolutionary Biology Program, Department of Ecology and Genetics (IEG), Uppsala University, SE-752 36 Uppsala, Sweden
| | - Christer Wiklund
- Department of Zoology: Division of Ecology, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Roger Vila
- Butterfly Diversity and Evolution Lab, Institut de Biologia Evolutiva (CSIC-UPF), 08003 Barcelona, Spain
| | - Peter Pruisscher
- Evolutionary Biology Program, Department of Ecology and Genetics (IEG), Uppsala University, SE-752 36 Uppsala, Sweden
| | - Niclas Backström
- Evolutionary Biology Program, Department of Ecology and Genetics (IEG), Uppsala University, SE-752 36 Uppsala, Sweden
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2
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Wilcox JJS, Arca-Ruibal B, Samour J, Mateuta V, Idaghdour Y, Boissinot S. Linked-Read Sequencing of Eight Falcons Reveals a Unique Genomic Architecture in Flux. Genome Biol Evol 2022; 14:evac090. [PMID: 35700227 PMCID: PMC9214253 DOI: 10.1093/gbe/evac090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 05/27/2022] [Accepted: 06/06/2022] [Indexed: 11/12/2022] Open
Abstract
Falcons are diverse birds of cultural and economic importance. They have undergone major lineage-specific chromosomal rearrangements, resulting in greatly-reduced chromosome counts relative to other birds. Here, we use 10X Genomics linked reads to provide new high-contiguity genomes for two gyrfalcons, a saker falcon, a lanner falcon, three subspecies of peregrine falcons, and the common kestrel. Assisted by a transcriptome sequenced from 22 gyrfalcon tissues, we annotate these genomes for a variety of genomic features, estimate historical demography, and then investigate genomic equilibrium in the context of falcon-specific chromosomal rearrangements. We find that falcon genomes are not in AT-GC equilibrium with a bias in substitutions towards higher AT content; this bias is predominantly but not exclusively driven by hypermutability of CpG sites. Small indels and large structural variants were also biased towards insertions rather than deletions. Patterns of disequilibrium were linked to chromosomal rearrangements: falcons have lost GC content in regions that have fused to larger chromosomes from microchromosomes and gained GC content in regions of macrochromosomes that have translocated to microchromosomes. Inserted bases have accumulated on regions ancestrally belonging to microchromosomes, consistent with insertion-biased gene conversion. We also find an excess of interspersed repeats on regions of microchromosomes that have fused to macrochromosomes. Our results reveal that falcon genomes are in a state of flux. They further suggest that many of the key differences between microchromosomes and macrochromosomes are driven by differences in chromosome size, and indicate a clear role for recombination and biased-gene-conversion in determining genomic equilibrium.
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Affiliation(s)
- Justin J S Wilcox
- Center for Genomics & Systems Biology, New York University Abu Dhabi, Saadiyat Island, Abu Dhabi, United Arab Emirates
| | | | - Jaime Samour
- Wildlife Management and Falcon Medicine and Breeding Consultancy, Abu Dhabi, United Arab Emirates
| | | | - Youssef Idaghdour
- Center for Genomics & Systems Biology, New York University Abu Dhabi, Saadiyat Island, Abu Dhabi, United Arab Emirates
- Biology Program, New York University Abu Dhabi, Saadiyat Island, Abu Dhabi, United Arab Emirates
| | - Stéphane Boissinot
- Center for Genomics & Systems Biology, New York University Abu Dhabi, Saadiyat Island, Abu Dhabi, United Arab Emirates
- Biology Program, New York University Abu Dhabi, Saadiyat Island, Abu Dhabi, United Arab Emirates
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3
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Barton HJ, Zeng K. The Impact of Natural Selection on Short Insertion and Deletion Variation in the Great Tit Genome. Genome Biol Evol 2019; 11:1514-1524. [PMID: 30924871 PMCID: PMC6543879 DOI: 10.1093/gbe/evz068] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/27/2019] [Indexed: 12/11/2022] Open
Abstract
Insertions and deletions (INDELs) remain understudied, despite being the most common form of genetic variation after single nucleotide polymorphisms. This stems partly from the challenge of correctly identifying the ancestral state of an INDEL and thus identifying it as an insertion or a deletion. Erroneously assigned ancestral states can skew the site frequency spectrum, leading to artificial signals of selection. Consequently, the selective pressures acting on INDELs are, at present, poorly resolved. To tackle this issue, we have recently published a maximum likelihood approach to estimate the mutation rate and the distribution of fitness effects for INDELs. Our approach estimates and controls for the rate of ancestral state misidentification, overcoming issues plaguing previous INDEL studies. Here, we apply the method to INDEL polymorphism data from ten high coverage (∼44×) European great tit (Parus major) genomes. We demonstrate that coding INDELs are under strong purifying selection with a small proportion making it into the population (∼4%). However, among fixed coding INDELs, 71% of insertions and 86% of deletions are fixed by positive selection. In noncoding regions, we estimate ∼80% of insertions and ∼52% of deletions are effectively neutral, the remainder show signatures of purifying selection. Additionally, we see evidence of linked selection reducing INDEL diversity below background levels, both in proximity to exons and in areas of low recombination.
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Affiliation(s)
- Henry J Barton
- Department of Animal and Plant Sciences, University of Sheffield, United Kingdom
| | - Kai Zeng
- Department of Animal and Plant Sciences, University of Sheffield, United Kingdom
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4
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Heissl A, Betancourt AJ, Hermann P, Povysil G, Arbeithuber B, Futschik A, Ebner T, Tiemann-Boege I. The impact of poly-A microsatellite heterologies in meiotic recombination. Life Sci Alliance 2019; 2:2/2/e201900364. [PMID: 31023833 PMCID: PMC6485458 DOI: 10.26508/lsa.201900364] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 03/27/2019] [Accepted: 03/29/2019] [Indexed: 12/12/2022] Open
Abstract
Meiosis strongly influences the transmission and evolution of heterozygous poly-A repeats as measured experimentally in a large collection of single recombination products in a human hotspot. Meiotic recombination has strong, but poorly understood effects on short tandem repeat (STR) instability. Here, we screened thousands of single recombinant products with sperm typing to characterize the role of polymorphic poly-A repeats at a human recombination hotspot in terms of hotspot activity and STR evolution. We show that the length asymmetry between heterozygous poly-A’s strongly influences the recombination outcome: a heterology of 10 A’s (9A/19A) reduces the number of crossovers and elevates the frequency of non-crossovers, complex recombination products, and long conversion tracts. Moreover, the length of the heterology also influences the STR transmission during meiotic repair with a strong and significant insertion bias for the short heterology (6A/7A) and a deletion bias for the long heterology (9A/19A). In spite of this opposing insertion-/deletion-biased gene conversion, we find that poly-A’s are enriched at human recombination hotspots that could have important consequences in hotspot activation.
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Affiliation(s)
- Angelika Heissl
- Institute of Biophysics, Johannes Kepler University, Linz, Austria
| | | | - Philipp Hermann
- Institute of Applied Statistics, Johannes Kepler University, Linz, Austria
| | - Gundula Povysil
- Institute of Bioinformatics, Johannes Kepler University, Linz, Austria
| | | | - Andreas Futschik
- Institute of Applied Statistics, Johannes Kepler University, Linz, Austria
| | - Thomas Ebner
- Department of Gynecology, Obstetrics and Gynecological Endocrinology, Kepler University Clinic, Linz, Austria
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Barton HJ, Zeng K. New Methods for Inferring the Distribution of Fitness Effects for INDELs and SNPs. Mol Biol Evol 2019; 35:1536-1546. [PMID: 29635416 PMCID: PMC5967470 DOI: 10.1093/molbev/msy054] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Small insertions and deletions (INDELs; ≤50 bp) are the most common type of variability after single nucleotide polymorphism (SNP). However, compared with SNPs, we know little about the distribution of fitness effects (DFE) of new INDEL mutations and how prevalent adaptive INDEL substitutions are. Studying INDELs has been difficult partly because identifying ancestral states at these sites is error-prone and misidentification can lead to severely biased estimates of the strength of selection. To solve these problems, we develop new maximum likelihood methods, which use polymorphism data to simultaneously estimate the DFE, the mutation rate, and the misidentification rate. These methods are applicable to both INDELs and SNPs. Simulations show that they can provide highly accurate results. We applied the methods to an INDEL polymorphism data set in Drosophila melanogaster. We found that the DFE for polymorphic INDELs in protein-coding regions is bimodal, with the variants being either nearly neutral or strongly deleterious. Based on the DFE, we estimated that 71.5–83.7% of the INDEL substitutions that took place along the D. melanogaster lineage were fixed by positive selection, which is comparable with the prevalence of adaptive substitutions at nonsynonymous sites. The new methods have been implemented in the software package anavar.
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Affiliation(s)
- Henry J Barton
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, United Kingdom
| | - Kai Zeng
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, United Kingdom
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Jia X, Zhang Y, Zhang Q, Zhao Q, Traw MB, Wang L, Tian D, Wang C, Yang S. High-resolution insight into recombination events at the SD1 locus in rice. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2019; 97:683-692. [PMID: 30417595 DOI: 10.1111/tpj.14154] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 09/28/2018] [Accepted: 11/05/2018] [Indexed: 06/09/2023]
Abstract
Recombination during meiosis plays an important role in genome evolution by reshuffling existing genetic variations into fresh combinations with the possibility of recovery of lost ancestral genotypes. While crossover (CO) events have been well studied, gene conversion events (GCs), which represent non-reciprocal information transfer between chromosomes, are poorly documented and difficult to detect due to their relatively small converted tract size. Here, we document these GC events and their phenotypic effects at an important locus in rice containing the SD1 gene, where multiple defective alleles contributed to the semi-dwarf phenotype of rice in the 'Green Revolution' of the 1960s. Here, physical separation of two defects allows recombination to generate the wild-type SD1 gene, for which plant height can then be used as a reporter. By screening 18 000 F2 progeny from a cross between two semi-dwarf cultivars that carry these different defective alleles, we detected 24 GC events, indicating a conversion rate of ~3.3 × 10-4 per marker per generation in a single meiotic cycle in rice. Furthermore, our data show that indels and single-nucleotide polymorphisms (SNPs) do not differ significantly in GC rates, at least at the SD1 locus. Our results provide strong evidence that GC by itself can regain an ancestral phenotype that was lost through mutation. This GC detection approach is likely to be broadly applicable to natural or artificial alleles of other phenotype-related functional genes, which are abundant in other plant genomes.
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Affiliation(s)
- Xianqing Jia
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, 210023, China
| | - Yadong Zhang
- Institute of Food Crops, Jiangsu Academy of Agricultural Sciences, Nanjing, 210014, China
| | - Qijun Zhang
- Institute of Food Crops, Jiangsu Academy of Agricultural Sciences, Nanjing, 210014, China
| | - Qingyong Zhao
- Institute of Food Crops, Jiangsu Academy of Agricultural Sciences, Nanjing, 210014, China
| | - Milton Brian Traw
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, 210023, China
| | - Long Wang
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, 210023, China
| | - Dacheng Tian
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, 210023, China
| | - Cailin Wang
- Institute of Food Crops, Jiangsu Academy of Agricultural Sciences, Nanjing, 210014, China
| | - Sihai Yang
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, 210023, China
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7
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Zhai Y, Alexandre BC. A Poissonian Model of Indel Rate Variation for Phylogenetic Tree Inference. Syst Biol 2018; 66:698-714. [PMID: 28204784 DOI: 10.1093/sysbio/syx033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 01/27/2017] [Indexed: 01/22/2023] Open
Abstract
While indel rate variation has been observed and analyzed in detail, it is not taken into account by current indel-aware phylogenetic reconstruction methods. In this work, we introduce a continuous time stochastic process, the geometric Poisson indel process, that generalizes the Poisson indel process by allowing insertion and deletion rates to vary across sites. We design an efficient algorithm for computing the probability of a given multiple sequence alignment based on our new indel model. We describe a method to construct phylogeny estimates from a fixed alignment using neighbor joining. Using simulation studies, we show that ignoring indel rate variation may have a detrimental effect on the accuracy of the inferred phylogenies, and that our proposed method can sidestep this issue by inferring latent indel rate categories. We also show that our phylogenetic inference method may be more stable to taxa subsampling than methods that either ignore indels or indel rate variation. [evolutionary stochastic process; indel rate variation; Poisson indel process; TKF91.].
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Affiliation(s)
- Yongliang Zhai
- Department of Statistics, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
| | - Bouchard-Côté Alexandre
- Department of Statistics, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
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8
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The rate of meiotic gene conversion varies by sex and age. Nat Genet 2016; 48:1377-1384. [PMID: 27643539 PMCID: PMC5083143 DOI: 10.1038/ng.3669] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Accepted: 08/16/2016] [Indexed: 12/14/2022]
Abstract
Meiotic recombination involves a combination of gene conversion and crossover events that, along with mutations, produce germline genetic diversity. Here we report the discovery of 3,176 SNP and 61 indel gene conversions. Our estimate of the non-crossover (NCO) gene conversion rate (G) is 7.0 for SNPs and 5.8 for indels per megabase per generation, and the GC bias is 67.6%. For indels, we demonstrate a 65.6% preference for the shorter allele. NCO gene conversions from mothers are longer than those from fathers, and G is 2.17 times greater in mothers. Notably, G increases with the age of mothers, but not the age of fathers. A disproportionate number of NCO gene conversions in older mothers occur outside double-strand break (DSB) regions and in regions with relatively low GC content. This points to age-related changes in the mechanisms of meiotic gene conversion in oocytes.
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Sloan DB, Wu Z. History of plastid DNA insertions reveals weak deletion and at mutation biases in angiosperm mitochondrial genomes. Genome Biol Evol 2014; 6:3210-21. [PMID: 25416619 PMCID: PMC4986453 DOI: 10.1093/gbe/evu253] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Angiosperm mitochondrial genomes exhibit many unusual properties, including heterogeneous nucleotide composition and exceptionally large and variable genome sizes. Determining the role of nonadaptive mechanisms such as mutation bias in shaping the molecular evolution of these unique genomes has proven challenging because their dynamic structures generally prevent identification of homologous intergenic sequences for comparative analyses. Here, we report an analysis of angiosperm mitochondrial DNA sequences that are derived from inserted plastid DNA (mtpts). The availability of numerous completely sequenced plastid genomes allows us to infer the evolutionary history of these insertions, including the specific nucleotide substitutions and indels that have occurred because their incorporation into the mitochondrial genome. Our analysis confirmed that many mtpts have a complex history, including frequent gene conversion and multiple examples of horizontal transfer between divergent angiosperm lineages. Nevertheless, it is clear that the majority of extant mtpt sequence in angiosperms is the product of recent transfer (or gene conversion) and is subject to rapid loss/deterioration, suggesting that most mtpts are evolving relatively free from functional constraint. The evolution of mtpt sequences reveals a pattern of biased mutational input in angiosperm mitochondrial genomes, including an excess of small deletions over insertions and a skew toward nucleotide substitutions that increase AT content. However, these mutation biases are far weaker than have been observed in many other cellular genomes, providing insight into some of the notable features of angiosperm mitochondrial architecture, including the retention of large intergenic regions and the relatively neutral GC content found in these regions.
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Affiliation(s)
- Daniel B Sloan
- Department of Biology, Colorado State University, Fort Collins
| | - Zhiqiang Wu
- Department of Biology, Colorado State University, Fort Collins
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Kvikstad EM, Duret L. Strong heterogeneity in mutation rate causes misleading hallmarks of natural selection on indel mutations in the human genome. Mol Biol Evol 2013; 31:23-36. [PMID: 24113537 PMCID: PMC3879449 DOI: 10.1093/molbev/mst185] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Elucidating the mechanisms of mutation accumulation and fixation is critical to understand the nature of genetic variation and its contribution to genome evolution. Of particular interest is the effect of insertions and deletions (indels) on the evolution of genome landscapes. Recent population-scaled sequencing efforts provide unprecedented data for analyzing the relative impact of selection versus nonadaptive forces operating on indels. Here, we combined McDonald-Kreitman tests with the analysis of derived allele frequency spectra to investigate the dynamics of allele fixation of short (1-50 bp) indels in the human genome. Our analyses revealed apparently higher fixation probabilities for insertions than deletions. However, this fixation bias is not consistent with either selection or biased gene conversion and varies with local mutation rate, being particularly pronounced at indel hotspots. Furthermore, we identified an unprecedented number of loci with evidence for multiple indel events in the primate phylogeny. Even in nonrepetitive sequence contexts (a priori not prone to indel mutations), such loci are 60-fold more frequent than expected according to a model of uniform indel mutation rate. This provides evidence of as yet unidentified cryptic indel hotspots. We propose that indel homoplasy, at known and cryptic hotspots, produces systematic errors in determination of ancestral alleles via parsimony and advise caution interpreting classic selection tests given the strong heterogeneity in indel rates across the genome. These results will have great impact on studies seeking to infer evolutionary forces operating on indels observed in closely related species, because such mutations are traditionally presumed homoplasy-free.
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Affiliation(s)
- Erika M Kvikstad
- Laboratoire de Biométrie et Biologie Evolutive, UMR 5558, CNRS, Université Lyon 1, Villeurbanne, France
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