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  • 1.
    Burri, Reto
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Nater, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Kawakami, Takeshi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Mugal, Carina F.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ólason, Páll I.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution.
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Suh, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Dutoit, Ludovic
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Bures, Stanislav
    Palacky Univ, Dept Zool, Lab Ornithol, Olomouc 77146, Czech Republic..
    Garamszegi, Laszlo Z.
    CSIC, Dept Evolutionary Ecol, Estn Biol Donana, Seville 41092, Spain..
    Hogner, Silje
    Univ Oslo, Ctr Ecol & Evolutionary Synth, Dept Biosci, N-0316 Oslo, Norway.;Univ Oslo, Nat Hist Museum, N-0318 Oslo, Norway..
    Moreno, Juan
    CSIC, Museo Nacl Ciencias Nat, E-28006 Madrid, Spain..
    Qvarnström, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Ruzic, Milan
    Bird Protect & Study Soc Serbia, Novi Sad 21000, Serbia..
    Saether, Stein-Are
    Univ Oslo, Ctr Ecol & Evolutionary Synth, Dept Biosci, N-0316 Oslo, Norway.;Norwegian Inst Nat Res NINA, N-7034 Trondheim, Norway..
    Saetre, Glenn-Peter
    Univ Oslo, Ctr Ecol & Evolutionary Synth, Dept Biosci, N-0316 Oslo, Norway..
    Toeroek, Janos
    Eotvos Lorand Univ, Dept Systemat Zool & Ecol, Behav Ecol Grp, H-1117 Budapest, Hungary..
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Linked selection and recombination rate variation drive the evolution of the genomic landscape of differentiation across the speciation continuum of Ficedula flycatchers2015In: Genome Research, ISSN 1088-9051, E-ISSN 1549-5469, Vol. 25, no 11, p. 1656-1665Article in journal (Refereed)
    Abstract [en]

    Speciation is a continuous process during which genetic changes gradually accumulate in the genomes of diverging species. Recent studies have documented highly heterogeneous differentiation landscapes, with distinct regions of elevated differentiation ("differentiation islands") widespread across genomes. However, it remains unclear which processes drive the evolution of differentiation islands; how the differentiation landscape evolves as speciation advances; and ultimately, how differentiation islands are related to speciation. Here, we addressed these questions based on population genetic analyses of 200 resequenced genomes from 10 populations of four Ficedula flycatcher sister species. We show that a heterogeneous differentiation landscape starts emerging among populations within species, and differentiation islands evolve recurrently in the very same genomic regions among independent lineages. Contrary to expectations from models that interpret differentiation islands as genomic regions involved in reproductive isolation that are shielded from gene flow, patterns of sequence divergence (d(XY) relative node depth) do not support a major role of gene flow in the evolution of the differentiation landscape in these species. Instead, as predicted by models of linked selection, genome-wide variation in diversity and differentiation can be explained by variation in recombination rate and the density of targets for selection. We thus conclude that the heterogeneous landscape of differentiation in Ficedula flycatchers evolves mainly as the result of background selection and selective sweeps in genomic regions of low recombination. Our results emphasize the necessity of incorporating linked selection as a null model to identify genome regions involved in adaptation and speciation.

  • 2.
    Dutoit, Ludovic
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Mugal, Carina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Bolivar, Paulina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Wang, Mi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Nadachowska-Brzyska, Krystyna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Gustafsson, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Sex-biased gene expression, sexual antagonism and levels of genetic diversity in the collared flycatcher (Ficedula albicollis) genome2018In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 27, no 18, p. 3572-3581Article in journal (Other academic)
    Abstract [en]

    Theoretical work suggests that sexual conflict should promote the maintenance of genetic diversity by the opposing directions of selection on sexually antagonistic mutations in males and females. This prediction, so far not been empirically tested on a genome-wide scale, could potentially contribute towards genomic heterogeneity in levels of genetic diversity. We used large-scale population genomic and transcriptomic data from the collared flycatcher (Ficedula albicollis) to analyse how sex-biased gene expression – one outcome of sexual conflict – relates to genetic variability. Here, we demonstrate that the extent of sex-biased gene expression of both male-biased and female-biased genes is significantly correlated with levels of nucleotide diversity in gene sequences and that this correlation extends to the overall levels of genomic diversity. We find evidence for balancing selection in sex-biased genes, suggesting that sex-biased gene expression could be seen as a component counteracting the diversity-reducing effects of linked positive and purifying selection. The observation of significant genetic differentiation between males and females for male-biased genes indicates ongoing sexual conflict and sex-specific viability selection, potentially driven by sexual selection. Our results thus provide a new perspective on the long-standing question in evolutionary biology of how genomes can remain so genetically variable in face of strong natural and sexual selection.

  • 3.
    Ekblom, Robert
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Brechlin, Birte
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Persson, Jens
    Swedish Univ Agr Sci, Dept Ecol, Grimso Wildlife Res Stn, Riddarhyttan, Sweden.
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Johansson, Malin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Magnusson, Jessica
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Flagstad, Oystein
    Norwegian Inst Nat Res, Trondheim, Norway.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Genome sequencing and conservation genomics in the Scandinavian wolverine population2018In: Conservation Biology, ISSN 0888-8892, E-ISSN 1523-1739, Vol. 32, no 6, p. 1301-1312Article in journal (Refereed)
    Abstract [en]

    Genetic approaches have proved valuable to the study and conservation of endangered populations, especially for monitoring programs, and there is potential for further developments in this direction by extending analyses to the genomic level. We assembled the genome of the wolverine (Gulo gulo), a mustelid that in Scandinavia has recently recovered from a significant population decline, and obtained a 2.42 Gb draft sequence representing >85% of the genome and including >21,000 protein-coding genes. We then performed whole-genome resequencing of 10 Scandinavian wolverines for population genomic and demographic analyses. Genetic diversity was among the lowest detected in a red-listed population (mean genome-wide nucleotide diversity of 0.05%). Results of the demographic analyses indicated a long-term decline of the effective population size (N-e) from 10,000 well before the last glaciation to N-e appeared even lower. The genome-wide F-IS level was 0.089 (possibly signaling inbreeding), but this effect was not observed when analyzing a set of highly variable SNP markers, illustrating that such markers can give a biased picture of the overall character of genetic diversity. We found significant population structure, which has implications for population connectivity and conservation. We used an integrated microfluidic circuit chip technology to develop an SNP-array consisting of 96 highly informative markers that, together with a multiplex pre-amplification step, was successfully applied to low-quality DNA from scat samples. Our findings will inform management, conservation, and genetic monitoring of wolverines and serve as a genomic roadmap that can be applied to other endangered species. The approach used here can be generally utilized in other systems, but we acknowledge the trade-off between investing in genomic resources and direct conservation actions.

  • 4.
    Ekblom, Robert
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Patterns of sequencing coverage bias revealed by ultra-deep sequencing of vertebrate mitochondria2014In: BMC Genomics, ISSN 1471-2164, E-ISSN 1471-2164, Vol. 15, p. 467-Article in journal (Refereed)
    Abstract [en]

    Background: Genome and transcriptome sequencing applications that rely on variation in sequence depth can be negatively affected if there are systematic biases in coverage. We have investigated patterns of local variation in sequencing coverage by utilising ultra-deep sequencing (>100,000X) of mtDNA obtained during sequencing of two vertebrate genomes, wolverine (Gulo gulo) and collared flycatcher (Ficedula albicollis). With such extreme depth, stochastic variation in coverage should be negligible, which allows us to provide a very detailed, fine-scale picture of sequence dependent coverage variation and sequencing error rates. Results: Sequencing coverage showed up to six-fold variation across the complete mtDNA and this variation was highly repeatable in sequencing of multiple individuals of the same species. Moreover, coverage in orthologous regions was correlated between the two species and was negatively correlated with GC content. We also found a negative correlation between the site-specific sequencing error rate and coverage, with certain sequence motifs "CCNGCC" being particularly prone to high rates of error and low coverage. Conclusions: Our results demonstrate that inherent sequence characteristics govern variation in coverage and suggest that some of this variation, like GC content, should be controlled for in, for example, RNA-Seq and detection of copy number variation.

  • 5.
    Ellegren, Hans
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Burri, Reto
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ólason, Páll I.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Backström, Niclas
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Kawakami, Takeshi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Künstner, Axel
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Mäkinen, Hannu
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Nadachowska-Brzyska, Krystyna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Qvarnström, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal Ecology.
    Uebbing, Severin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Wolf, Jochen B. W.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    The genomic landscape of species divergence in Ficedula flycatchers2012In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 491, no 7426, p. 756-760Article in journal (Refereed)
    Abstract [en]

    Unravelling the genomic landscape of divergence between lineages is key to understanding speciation. The naturally hybridizing collared flycatcher and pied flycatcher are important avian speciation models that show pre-as well as postzygotic isolation. We sequenced and assembled the 1.1-Gb flycatcher genome, physically mapped the assembly to chromosomes using a low-density linkage map and re-sequenced population samples of each species. Here we show that the genomic landscape of species differentiation is highly heterogeneous with approximately 50 'divergence islands' showing up to 50-fold higher sequence divergence than the genomic background. These non-randomly distributed islands, with between one and three regions of elevated divergence per chromosome irrespective of chromosome size, are characterized by reduced levels of nucleotide diversity, skewed allele-frequency spectra, elevated levels of linkage disequilibrium and reduced proportions of shared polymorphisms in both species, indicative of parallel episodes of selection. Proximity of divergence peaks to genomic regions resistant to sequence assembly, potentially including centromeres and telomeres, indicate that complex repeat structures may drive species divergence. A much higher background level of species divergence of the Z chromosome, and a lower proportion of shared polymorphisms, indicate that sex chromosomes and autosomes are at different stages of speciation. This study provides a roadmap to the emerging field of speciation genomics.

  • 6.
    Husby, Arild
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Kawakami, Takeshi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ronnegard, Lars
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Qvarnström, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Genome-wide association mapping in a wild avian population identifies a link between genetic and phenotypic variation in a life-history trait2015In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 282, no 1806Article in journal (Refereed)
    Abstract [en]

    Understanding the genetic basis of traits involved in adaptation is a major challenge in evolutionary biology but remains poorly understood. Here, we use genome-wide association mapping using a custom 50 k single nucleotide polymorphism (SNP) array in a natural population of collared flycatchers to examine the genetic basis of clutch size, an important life-history trait in many animal species. We found evidence for an association on chromosome 18 where one SNP significant at the genome-wide level explained 3.9% of the phenotypic variance. We also detected two suggestive quantitative trait loci (QTLs) on chromosomes 9 and 26. Fitness differences among genotypes were generally weak and not significant, although there was some indication of a sex-by-genotype interaction for lifetime reproductive success at the suggestive QTL on chromosome 26. This implies that sexual antagonism may play a role in maintaining genetic variation at this QTL. Our findings provide candidate regions for a classic avian life-history trait that will be useful for future studies examining the molecular and cellular function of, as well as evolutionary mechanisms operating at, these loci.

  • 7. Jarvis, Erich D.
    et al.
    Mirarab, Siavash
    Aberer, Andre J.
    Li, Bo
    Houde, Peter
    Li, Cai
    Ho, Simon Y. W.
    Faircloth, Brant C.
    Nabholz, Benoit
    Howard, Jason T.
    Suh, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Weber, Claudia C.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    da Fonseca, Rute R.
    Li, Jianwen
    Zhang, Fang
    Li, Hui
    Zhou, Long
    Narula, Nitish
    Liu, Liang
    Ganapathy, Ganesh
    Boussau, Bastien
    Bayzid, Md. Shamsuzzoha
    Zavidovych, Volodymyr
    Subramanian, Sankar
    Gabaldon, Toni
    Capella-Gutierrez, Salvador
    Huerta-Cepas, Jaime
    Rekepalli, Bhanu
    Munch, Kasper
    Schierup, Mikkel
    Lindow, Bent
    Warren, Wesley C.
    Ray, David
    Green, Richard E.
    Bruford, Michael W.
    Zhan, Xiangjiang
    Dixon, Andrew
    Li, Shengbin
    Li, Ning
    Huang, Yinhua
    Derryberry, Elizabeth P.
    Bertelsen, Mads Frost
    Sheldon, Frederick H.
    Brumfield, Robb T.
    Mello, Claudio V.
    Lovell, Peter V.
    Wirthlin, Morgan
    Cruz Schneider, Maria Paula
    Prosdocimi, Francisco
    Samaniego, Jose Alfredo
    Vargas Velazquez, Amhed Missael
    Alfaro-Nunez, Alonzo
    Campos, Paula F.
    Petersen, Bent
    Sicheritz-Ponten, Thomas
    Pas, An
    Bailey, Tom
    Scofield, Paul
    Bunce, Michael
    Lambert, David M.
    Zhou, Qi
    Perelman, Polina
    Driskell, Amy C.
    Shapiro, Beth
    Xiong, Zijun
    Zeng, Yongli
    Liu, Shiping
    Li, Zhenyu
    Liu, Binghang
    Wu, Kui
    Xiao, Jin
    Yinqi, Xiong
    Zheng, Qiuemei
    Zhang, Yong
    Yang, Huanming
    Wang, Jian
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Rheindt, Frank E.
    Braun, Michael
    Fjeldsa, Jon
    Orlando, Ludovic
    Barker, F. Keith
    Jonsson, Knud Andreas
    Johnson, Warren
    Koepfli, Klaus-Peter
    O'Brien, Stephen
    Haussler, David
    Ryder, Oliver A.
    Rahbek, Carsten
    Willerslev, Eske
    Graves, Gary R.
    Glenn, Travis C.
    McCormack, John
    Burt, Dave
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Alstrom, Per
    Edwards, Scott V.
    Stamatakis, Alexandros
    Mindell, David P.
    Cracraft, Joel
    Braun, Edward L.
    Warnow, Tandy
    Jun, Wang
    Gilbert, M. Thomas P.
    Zhang, Guojie
    Whole-genome analyses resolve early branches in the tree of life of modern birds2014In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 346, no 6215, p. 1320-1331Article in journal (Refereed)
    Abstract [en]

    To better determine the history of modern birds, we performed a genome-scale phylogenetic analysis of 48 species representing all orders of Neoaves using phylogenomic methods created to handle genome-scale data. We recovered a highly resolved tree that confirms previously controversial sister or close relationships. We identified the first divergence in Neoaves, two groups we named Passerea and Columbea, representing independent lineages of diverse and convergently evolved land and water bird species. Among Passerea, we infer the common ancestor of core landbirds to have been an apex predator and confirm independent gains of vocal learning. Among Columbea, we identify pigeons and flamingoes as belonging to sister clades. Even with whole genomes, some of the earliest branches in Neoaves proved challenging to resolve, which was best explained by massive protein-coding sequence convergence and high levels of incomplete lineage sorting that occurred during a rapid radiation after the Cretaceous-Paleogene mass extinction event about 66 million years ago.

  • 8.
    Kawakami, Takeshi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology. Univ Sheffield, Dept Anim & Plant Sci, Sheffield, S Yorkshire, England..
    Mugal, Carina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Suh, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Nater, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology. Univ Zurich, Dept Evolutionary Biol & Environm Studies, Zurich, Switzerland..
    Burri, Reto
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology. Friedrich Schiller Univ Jena, Dept Populat Ecol, Jena, Germany..
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Whole-genome patterns of linkage disequilibrium across flycatcher populations clarify the causes and consequences of fine-scale recombination rate variation in birds2017In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 26, no 16, p. 4158-4172Article in journal (Refereed)
    Abstract [en]

    Recombination rate is heterogeneous across the genome of various species and so are genetic diversity and differentiation as a consequence of linked selection. However, we still lack a clear picture of the underlying mechanisms for regulating recombination. Here we estimated fine-scale population recombination rate based on the patterns of linkage disequilibrium across the genomes of multiple populations of two closely related flycatcher species (Ficedula albicollis and F. hypoleuca). This revealed an overall conservation of the recombination landscape between these species at the scale of 200 kb, but we also identified differences in the local rate of recombination despite their recent divergence (<1 million years). Genetic diversity and differentiation were associated with recombination rate in a lineage-specific manner, indicating differences in the extent of linked selection between species. We detected 400-3,085 recombination hotspots per population. Location of hotspots was conserved between species, but the intensity of hotspot activity varied between species. Recombination hotspots were primarily associated with CpG islands (CGIs), regardless of whether CGIs were at promoter regions or away from genes. Recombination hotspots were also associated with specific transposable elements (TEs), but this association appears indirect due to shared preferences of the transposition machinery and the recombination machinery for accessible open chromatin regions. Our results suggest that CGIs are a major determinant of the localization of recombination hotspots, and we propose that both the distribution of TEs and fine-scale variation in recombination rate may be associated with the evolution of the epigenetic landscape.

  • 9.
    Kawakami, Takeshi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Backstrom, Niclas
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Husby, Arild
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Qvarnström, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Mugal, Carina F.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ólason, Páll
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    A high-density linkage map enables a second-generation collared flycatcher genome assembly and reveals the patterns of avian recombination rate variation and chromosomal evolution2014In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 23, no 16, p. 4035-4058Article, review/survey (Refereed)
    Abstract [en]

    Detailed linkage and recombination rate maps are necessary to use the full potential of genome sequencing and population genomic analyses. We used a custom collared flycatcher 50K SNP array to develop a high-density linkage map with 37262 markers assigned to 34 linkage groups in 33 autosomes and the Z chromosome. The best-order map contained 4215 markers, with a total distance of 3132cM and a mean genetic distance between markers of 0.12cM. Facilitated by the array being designed to include markers from most scaffolds, we obtained a second-generation assembly of the flycatcher genome that approaches full chromosome sequences (N50 super-scaffold size 20.2Mb and with 1.042Gb (of 1.116Gb) anchored to and mostly ordered and oriented along chromosomes). We found that flycatcher and zebra finch chromosomes are entirely syntenic but that inversions at mean rates of 1.5-2.0 event (6.6-7.5Mb) per My have changed the organization within chromosomes, rates high enough for inversions to potentially have been involved with many speciation events during avian evolution. The mean recombination rate was 3.1cM/Mb and correlated closely with chromosome size, from 2cM/Mb for chromosomes >100Mb to >10cM/Mb for chromosomes <10Mb. This size dependence seemed entirely due to an obligate recombination event per chromosome; if 50cM was subtracted from the genetic lengths of chromosomes, the rate per physical unit DNA was constant across chromosomes. Flycatcher recombination rate showed similar variation along chromosomes as chicken but lacked the large interior recombination deserts characteristic of zebra finch chromosomes.

  • 10. Lamatsch, Dunja K.
    et al.
    Adolfsson, Sofia
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Senior, Alistair M.
    Christiansen, Guntram
    Pichler, Maria
    Ozaki, Yuichi
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Schartl, Manfred
    Nakagawa, Shinichi
    A Transcriptome Derived Female-Specific Marker from the Invasive Western Mosquitofish (Gambusia affinis)2015In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 2, article id e0118214Article in journal (Refereed)
    Abstract [en]

    Sex-specific markers are a prerequisite for understanding reproductive biology, genetic factors involved in sex differences, mechanisms of sex determination, and ultimately the evolution of sex chromosomes. The Western mosquitofish, Gambusia affinis, may be considered a model species for sex-chromosome evolution, as it displays female heterogamety (ZW/ZZ), and is also ecologically interesting as a worldwide invasive species. Here, de novo RNA-sequencing on the gonads of sexually mature G. affinis was used to identify contigs that were highly transcribed in females but not in males (i.e., transcripts with ovary-specific expression). Subsequently, 129 primer pairs spanning 79 contigs were tested by PCR to identify sex-specific transcripts. Of those primer pairs, one female-specific DNA marker was identified, Sanger sequenced and subsequently validated in 115 fish. Sequence analyses revealed a high similarity between the identified sex-specific marker and the 3' UTR of the aminomethyl transferase (amt) gene of the closely related platyfish (Xiphophorus maculatus). This is the first time that RNA-seq has been used to successfully characterize a sex-specific marker in a fish species in the absence of a genome map. Additionally, the identified sex-specific marker represents one of only a handful of such markers in fishes.

  • 11.
    Nadachowska-Brzyska, Krystyna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Burri, Reto
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Olason, Pall
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Kawakami, Takeshi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Smeds, Linnéa
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Demographic Divergence History of Pied Flycatcher and Collared Flycatcher Inferred from Whole-Genome Re-sequencing Data2013In: PLOS Genetics, ISSN 1553-7390, E-ISSN 1553-7404, Vol. 9, no 11, p. e1003942-Article in journal (Refereed)
    Abstract [en]

    Profound knowledge of demographic history is a prerequisite for the understanding and inference of processes involved in the evolution of population differentiation and speciation. Together with new coalescent-based methods, the recent availability of genome-wide data enables investigation of differentiation and divergence processes at unprecedented depth. We combined two powerful approaches, full Approximate Bayesian Computation analysis (ABC) and pairwise sequentially Markovian coalescent modeling (PSMC), to reconstruct the demographic history of the split between two avian speciation model species, the pied flycatcher and collared flycatcher. Using whole-genome re-sequencing data from 20 individuals, we investigated 15 demographic models including different levels and patterns of gene flow, and changes in effective population size over time. ABC provided high support for recent (mode 0.3 my, range <0.7 my) species divergence, declines in effective population size of both species since their initial divergence, and unidirectional recent gene flow from pied flycatcher into collared flycatcher. The estimated divergence time and population size changes, supported by PSMC results, suggest that the ancestral species persisted through one of the glacial periods of middle Pleistocene and then split into two large populations that first increased in size before going through severe bottlenecks and expanding into their current ranges. Secondary contact appears to have been established after the last glacial maximum. The severity of the bottlenecks at the last glacial maximum is indicated by the discrepancy between current effective population sizes (20,000–80,000) and census sizes (5–50 million birds) of the two species. The recent divergence time challenges the supposition that avian speciation is a relatively slow process with extended times for intrinsic postzygotic reproductive barriers to evolve. Our study emphasizes the importance of using genome-wide data to unravel tangled demographic histories. Moreover, it constitutes one of the first examples of the inference of divergence history from genome-wide data in non-model species.

  • 12.
    Nadachowska-Brzyska, Krystyna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Burri, Reto
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    PSMC analysis of effective population sizes in molecular ecology and its application to black-and-white Ficedula flycatchers2016In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 25, no 5, p. 1058-1072Article, review/survey (Refereed)
    Abstract [en]

    Climatic fluctuations during the Quaternary period governed the demography of species and contributed to population differentiation and ultimately speciation. Studies of these past processes have previously been hindered by a lack of means and genetic data to model changes in effective population size (N-e) through time. However, based on diploid genome sequences of high quality, the recently developed pairwise sequentially Markovian coalescent (PSMC) can estimate trajectories of changes in N-e over considerable time periods. We applied this approach to resequencing data from nearly 200 genomes of four species and several populations of the Ficedula species complex of black-and-white flycatchers. N-e curves of Atlas, collared, pied and semicollared flycatcher converged 1-2million years ago (Ma) at an N-e of approximate to 200000, likely reflecting the time when all four species last shared a common ancestor. Subsequent separate N-e trajectories are consistent with lineage splitting and speciation. All species showed evidence of population growth up until 100-200thousand years ago (kya), followed by decline and then start of a new phase of population expansion. However, timing and amplitude of changes in N-e differed among species, and for pied flycatcher, the temporal dynamics of N-e differed between Spanish birds and central/northern European populations. This cautions against extrapolation of demographic inference between lineages and calls for adequate sampling to provide representative pictures of the coalescence process in different species or populations. We also empirically evaluate criteria for proper inference of demographic histories using PSMC and arrive at recommendations of using sequencing data with a mean genome coverage of 18X, a per-site filter of 10 reads and no more than 25% of missing data.

  • 13.
    Nadachowska-Brzyska, Krystyna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Li, Cai
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Zhang, Guojie
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Temporal Dynamics of Avian Populations during Pleistocene Revealed by Whole-Genome Sequences2015In: Current Biology, ISSN 0960-9822, E-ISSN 1879-0445, Vol. 25, no 10, p. 1375-1380Article in journal (Refereed)
    Abstract [en]

    Global climate fluctuations have significantly influenced the distribution and abundance of biodiversity [1]. During unfavorable glacial periods, many species experienced range contraction and fragmentation, expanding again during interglacials [2- 4]. An understanding of the evolutionary consequences of both historical and ongoing climate changes requires knowledge of the temporal dynamics of population numbers during such climate cycles. Variation in abundance should have left clear signatures in the patterns of intraspecific genetic variation in extant species, from which historical effective population sizes (Ne) can be estimated [3]. We analyzed whole-genome sequences of 38 avian species in a pairwise sequentially Markovian coalescent (PSMC, [5]) framework to quantitatively reveal changes in Ne from approximately 10 million to 10 thousand years ago. Significant fluctuations in Ne over time were evident for most species. The most pronounced pattern observed in many species was a severe reduction in Ne coinciding with the beginning of the last glacial period (LGP). Among species, Ne varied by at least three orders of magnitude, exceeding 1 million in the most abundant species. Several species on the IUCN Red List of Threatened Species showed long-term reduction in population size, predating recent declines. We conclude that cycles of population expansions and contractions have been a common feature of many bird species during the Quaternary period, likely coinciding with climate cycles. Population size reduction should have increased the risk of extinction but may also have promoted speciation. Species that have experienced long-term declines may be especially vulnerable to recent anthropogenic threats.

  • 14.
    Nater, Alexander
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Burri, Reto
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Kawakami, Takeshi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Resolving Evolutionary Relationships in Closely Related Species with Whole-Genome Sequencing Data2015In: Systematic Biology, ISSN 1063-5157, E-ISSN 1076-836X, Vol. 64, no 6, p. 1000-1017Article in journal (Refereed)
    Abstract [en]

    Using genetic data to resolve the evolutionary relationships of species is of major interest in evolutionary and systematic biology. However, reconstructing the sequence of speciation events, the so-called species tree, in closely related and potentially hybridizing species is very challenging. Processes such as incomplete lineage sorting and interspecific gene flow result in local gene genealogies that differ in their topology from the species tree, and analyses of few loci with a single sequence per species are likely to produce conflicting or even misleading results. To study these phenomena on a full phylogenomic scale, we use whole-genome sequence data from 200 individuals of four black-and-white flycatcher species with so far unresolved phylogenetic relationships to infer gene tree topologies and visualize genome-wide patterns of gene tree incongruence. Using phylogenetic analysis in nonoverlapping 10-kb windows, we show that gene tree topologies are extremely diverse and change on a very small physical scale. Moreover, we find strong evidence for gene flow among flycatcher species, with distinct patterns of reduced introgression on the Z chromosome. To resolve species relationships on the background of widespread gene tree incongruence, we used four complementary coalescent-based methods for species tree reconstruction, including complex modeling approaches that incorporate post-divergence gene flow among species. This allowed us to infer the most likely species tree with high confidence. Based on this finding, we show that regions of reduced effective population size, which have been suggested as particularly useful for species tree inference, can produce positively misleading species tree topologies. Our findings disclose the pitfalls of using loci potentially under selection as phylogenetic markers and highlight the potential of modeling approaches to disentangle species relationships in systems with large effective population sizes and post-divergence gene flow.

  • 15.
    Smeds, Linnea
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Kawakami, Takeshi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Burri, Reto
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Bolivar, Paulina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Husby, Arild
    Qvarnström, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Uebbing, Severin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Genomic identification and characterization of the pseudoautosomal region in highly differentiated avian sex chromosomes2014In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, p. 5448-Article in journal (Refereed)
    Abstract [en]

    The molecular characteristics of the pseudoautosomal region (PAR) of sex chromosomes remain elusive. Despite significant genome-sequencing efforts, the PAR of highly differentiated avian sex chromosomes remains to be identified. Here we use linkage analysis together with whole-genome re-sequencing to uncover the 630-kb PAR of an ecological model species, the collared flycatcher. The PAR contains 22 protein-coding genes and is GC rich. The genetic length is 64cM in female meiosis, consistent with an obligate crossing-over event. Recombination is concentrated to a hotspot region, with an extreme rate of > 700 cM/Mb in a 67-kb segment. We find no signatures of sexual antagonism and propose that sexual antagonism may have limited influence on PAR sequences when sex chromosomes are nearly fully differentiated and when a recombination hotspot region is located close to the PAR boundary. Our results demonstrate that a very small PAR suffices to ensure homologous recombination and proper segregation of sex chromosomes during meiosis.

  • 16.
    Smeds, Linnea
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Kojola, Ilpo
    Nat Resources Inst Finland Luke, Rovaniemi, Finland.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    The evolutionary history of grey wolf Y chromosomes2019In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 28, no 9, p. 2173-2191Article in journal (Refereed)
    Abstract [en]

    Analyses of Y chromosome haplotypes uniquely provide a paternal picture of evolutionary histories and offer a very useful contrast to studies based on maternally inherited mitochondrial DNA (mtDNA). Here we used a bioinformatic approach based on comparison of male and female sequence coverage to identify 4.7 Mb from the grey wolf (Canis lupis) Y chromosome, probably representing most of the male-specific, nonampliconic sequence from the euchromatic part of the chromosome. We characterized this sequence and then identified approximate to 1,500 Y-linked single nucleotide polymorphisms in a sample of 145 resequenced male wolves, including 75 Finnish wolf genomes newly sequenced in this study, and in 24 dogs and eight other canids. We found 53 Y chromosome haplotypes, of which 26 were seen in grey wolves, that clustered in four major haplogroups. All four haplogroups were represented in samples of Finnish wolves, showing that haplogroup lineages were not partitioned on a continental scale. However, regional population structure was indicated because individual haplotypes were never shared between geographically distant areas, and genetically similar haplotypes were only found within the same geographical region. The deepest split between grey wolf haplogroups was estimated to have occurred 125,000 years ago, which is considerably older than recent estimates of the time of divergence of wolf populations. The distribution of dogs in a phylogenetic tree of Y chromosome haplotypes supports multiple domestication events, or wolf paternal introgression, starting 29,000 years ago. We also addressed the disputed origin of a recently founded population of Scandinavian wolves and observed that founding as well as most recent immigrant haplotypes were present in the neighbouring Finnish population, but not in sequenced wolves from elsewhere in the world, or in dogs.

  • 17.
    Smeds, Linnea
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Künstner, Axel
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    ConDeTri: A content dependent read trimmer for Illumina data2011In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 6, no 10, p. e26314-Article in journal (Refereed)
    Abstract [en]

    During the last few years, DNA and RNA sequencing have started to play an increasingly important role in biological and medical applications, especially due to the greater amount of sequencing data yielded from the new sequencing machines and the enormous decrease in sequencing costs. Particularly, Illumina/Solexa sequencing has had an increasing impact on gathering data from model and non-model organisms. However, accurate and easy to use tools for quality filtering have not yet been established. We present ConDeTri, a method for content dependent read trimming for next generation sequencing data using quality scores of each individual base. The main focus of the method is to remove sequencing errors from reads so that sequencing reads can be standardized. Another aspect of the method is to incorporate read trimming in next-generation sequencing data processing and analysis pipelines. It can process single-end and paired-end sequence data of arbitrary length and it is independent from sequencing coverage and user interaction. ConDeTri is able to trim and remove reads with low quality scores to save computational time and memory usage during de novo assemblies.  Low coverage or large genome sequencing projects will especially gain from trimming reads.  The method can easily be incorporated into preprocessing and analysis pipelines for Illumina data.

    Availability and implementation:

    Freely available on the web athttp://code.google.com/p/condetri

  • 18.
    Smeds, Linnea
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Warmuth, Vera
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Bolivar, Paulina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Uebbing, Severin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Burri, Reto
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Suh, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Nater, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Bures, Stanislav
    Garamszegi, Laszlo Z.
    Hogner, Silje
    Moreno, Juan
    Qvarnström, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Ruzic, Milan
    Saether, Stein-Are
    Saetre, Glenn-Peter
    Torok, Janos
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Evolutionary analysis of the female-specific avian W chromosome2015In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 6, article id 7330Article in journal (Refereed)
    Abstract [en]

    The typically repetitive nature of the sex-limited chromosome means that it is often excluded from or poorly covered in genome assemblies, hindering studies of evolutionary and population genomic processes in non-recombining chromosomes. Here, we present a draft assembly of the non-recombining region of the collared flycatcher W chromosome, containing 46 genes without evidence of female-specific functional differentiation. Survival of genes during W chromosome degeneration has been highly non-random and expression data suggest that this can be attributed to selection for maintaining gene dose and ancestral expression levels of essential genes. Re-sequencing of large population samples revealed dramatically reduced levels of within-species diversity and elevated rates of between-species differentiation (lineage sorting), consistent with low effective population size. Concordance between W chromosome and mitochondrial DNA phylogenetic trees demonstrates evolutionary stable matrilineal inheritance of this nuclear-cytonuclear pair of chromosomes. Our results show both commonalities and differences between W chromosome and Y chromosome evolution.

  • 19.
    Smeds, Linnéa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Mugal, Carina F
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Qvarnström, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    High-Resolution Mapping of Crossover and Non-crossover Recombination Events by Whole-Genome Re-sequencing of an Avian Pedigree2016In: PLoS Genetics, ISSN 1553-7390, E-ISSN 1553-7404, Vol. 12, no 5, article id e1006044Article in journal (Refereed)
    Abstract [en]

    Recombination is an engine of genetic diversity and therefore constitutes a key process in evolutionary biology and genetics. While the outcome of crossover recombination can readily be detected as shuffled alleles by following the inheritance of markers in pedigreed families, the more precise location of both crossover and non-crossover recombination events has been difficult to pinpoint. As a consequence, we lack a detailed portrait of the recombination landscape for most organisms and knowledge on how this landscape impacts on sequence evolution at a local scale. To localize recombination events with high resolution in an avian system, we performed whole-genome re-sequencing at high coverage of a complete three-generation collared flycatcher pedigree. We identified 325 crossovers at a median resolution of 1.4 kb, with 86% of the events localized to <10 kb intervals. Observed crossover rates were in excellent agreement with data from linkage mapping, were 52% higher in male (3.56 cM/Mb) than in female meiosis (2.28 cM/Mb), and increased towards chromosome ends in male but not female meiosis. Crossover events were non-randomly distributed in the genome with several distinct hot-spots and a concentration to genic regions, with the highest density in promoters and CpG islands. We further identified 267 non-crossovers, whose location was significantly associated with crossover locations. We detected a significant transmission bias (0.18) in favour of 'strong' (G, C) over 'weak' (A, T) alleles at non-crossover events, providing direct evidence for the process of GC-biased gene conversion in an avian system. The approach taken in this study should be applicable to any species and would thereby help to provide a more comprehensive portray of the recombination landscape across organism groups.

  • 20.
    Suh, Alexander
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Abundant recent activity of retrovirus-like retrotransposons within and among flycatcher species implies a rich source of structural variation in songbird genomes2018In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 27, no 1, p. 99-111Article in journal (Refereed)
    Abstract [en]

    Transposable elements (TEs) are genomic parasites capable of inserting virtually anywhere in the host genome, with manifold consequences for gene expression, DNA methylation and genomic stability. Notably, they can contribute to phenotypic variation and hence be associated with, for example, local adaptation and speciation. However, some organisms such as birds have been widely noted for the low densities of TEs in their genomes and this has been attributed to a potential dearth in transposition during their evolution. Here, we show that avian evolution witnessed diverse and abundant transposition on very recent timescales. First, we made an in-depth repeat annotation of the collared flycatcher genome, including identification of 23 new, retrovirus-like LTR retrotransposon families. Then, using whole-genome resequencing data from 200 Ficedula flycatchers, we detected 11,888 polymorphic TE insertions (TE presence/absence variations, TEVs) that segregated within and among species. The density of TEVs was one every 1.5-2.5Mb per individual, with heterozygosities of 0.12-0.16. The majority of TEVs belonged to some 10 different LTR families, most of which are specific to the flycatcher lineage. TEVs were validated by tracing the segregation of hundreds of TEVs across a three-generation pedigree of collared flycatchers and also by their utility as markers recapitulating the phylogenetic relationships among flycatcher species. Our results suggest frequent germline invasions of songbird genomes by novel retroviruses as a rich source of structural variation, which may have had underappreciated phenotypic consequences for the diversification of this species-rich group of birds.

  • 21.
    Suh, Alexander
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    The Dynamics of Incomplete Lineage Sorting across the Ancient Adaptive Radiation of Neoavian Birds2015In: PLoS biology, ISSN 1544-9173, E-ISSN 1545-7885, Vol. 13, no 8, article id e1002224Article in journal (Refereed)
    Abstract [en]

    The diversification of neoavian birds is one of the most rapid adaptive radiations of extant organisms. Recent whole-genome sequence analyses have much improved the resolution of the neoavian radiation and suggest concurrence with the Cretaceous-Paleogene (K-Pg) boundary, yet the causes of the remaining genome-level irresolvabilities appear unclear. Here we show that genome-level analyses of 2,118 retrotransposon presence/absence markers converge at a largely consistent Neoaves phylogeny and detect a highly differential temporal prevalence of incomplete lineage sorting (ILS), i.e., the persistence of ancestral genetic variation as polymorphisms during speciation events. We found that ILS-derived incongruences are spread over the genome and involve 35% and 34% of the analyzed loci on the autosomes and the Z chromosome, respectively. Surprisingly, Neoaves diversification comprises three adaptive radiations, an initial near-K-Pg super-radiation with highly discordant phylogenetic signals from near-simultaneous speciation events, followed by two post-K-Pg radiations of core landbirds and core waterbirds with much less pronounced ILS. We provide evidence that, given the extreme level of up to 100% ILS per branch in super-radiations, particularly rapid speciation events may neither resemble a fully bifurcating tree nor are they resolvable as such. As a consequence, their complex demographic history is more accurately represented as local networks within a species tree.

  • 22. Warren, Wesley C
    et al.
    Clayton, David F
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Arnold, Arthur P
    Hillier, Ladeana W
    Künstner, Axel
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics.
    Searle, Steve
    White, Simon
    Vilella, Albert J
    Fairley, Susan
    Heger, Andreas
    Kong, Lesheng
    Ponting, Chris P
    Jarvis, Erich D
    Mello, Claudio V
    Minx, Pat
    Lovell, Peter
    Velho, Tarciso A F
    Ferris, Margaret
    Balakrishnan, Christopher N
    Sinha, Saurabh
    Blatti, Charles
    London, Sarah E
    Li, Yun
    Lin, Ya-Chi
    George, Julia
    Sweedler, Jonathan
    Southey, Bruce
    Gunaratne, Preethi
    Watson, Michael
    Nam, Kiwoong
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics.
    Backström, Niclas
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics.
    Smeds, Linnea
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics.
    Nabholz, Benoit
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics.
    Itoh, Yuichiro
    Whitney, Osceola
    Pfenning, Andreas R
    Howard, Jason
    Völker, Martin
    Skinner, Bejamin M
    Griffin, Darren K
    Ye, Liang
    McLaren, William M
    Flicek, Paul
    Quesada, Victor
    Velasco, Gloria
    Lopez-Otin, Carlos
    Puente, Xose S
    Olender, Tsviya
    Lancet, Doron
    Smit, Arian F A
    Hubley, Robert
    Konkel, Miriam K
    Walker, Jerilyn A
    Batzer, Mark A
    Gu, Wanjun
    Pollock, David D
    Chen, Lin
    Cheng, Ze
    Eichler, Evan E
    Stapley, Jessica
    Slate, Jon
    Ekblom, Robert
    Birkhead, Tim
    Burke, Terry
    Burt, David
    Scharff, Constance
    Adam, Iris
    Richard, Hugues
    Sultan, Marc
    Soldatov, Alexey
    Lehrach, Hans
    Edwards, Scott V
    Yang, Shiaw-Pyng
    Li, Xiaoching
    Graves, Tina
    Fulton, Lucinda
    Nelson, Joanne
    Chinwalla, Asif
    Hou, Shunfeng
    Mardis, Elaine R
    Wilson, Richard K
    The genome of a songbird2010In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 464, no 7289, p. 757-762Article in journal (Refereed)
    Abstract [en]

    The zebra finch is an important model organism in several fields with unique relevance to human neuroscience. Like other songbirds, the zebra finch communicates through learned vocalizations, an ability otherwise documented only in humans and a few other animals and lacking in the chicken-the only bird with a sequenced genome until now. Here we present a structural, functional and comparative analysis of the genome sequence of the zebra finch (Taeniopygia guttata), which is a songbird belonging to the large avian order Passeriformes. We find that the overall structures of the genomes are similar in zebra finch and chicken, but they differ in many intrachromosomal rearrangements, lineage-specific gene family expansions, the number of long-terminal-repeat-based retrotransposons, and mechanisms of sex chromosome dosage compensation. We show that song behaviour engages gene regulatory networks in the zebra finch brain, altering the expression of long non-coding RNAs, microRNAs, transcription factors and their targets. We also show evidence for rapid molecular evolution in the songbird lineage of genes that are regulated during song experience. These results indicate an active involvement of the genome in neural processes underlying vocal communication and identify potential genetic substrates for the evolution and regulation of this behaviour.

1 - 22 of 22
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