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1.
Genome Res ; 32(3): 449-458, 2022 03.
Artículo en Inglés | MEDLINE | ID: mdl-35135873

RESUMEN

Genetic drift can dramatically change allele frequencies in small populations and lead to reduced levels of genetic diversity, including loss of segregating variants. However, there is a shortage of quantitative studies of how genetic diversity changes over time in natural populations, especially on genome-wide scales. Here, we analyzed whole-genome sequences from 76 wolves of a highly inbred Scandinavian population, founded by only one female and two males, sampled over a period of 30 yr. We obtained chromosome-level haplotypes of all three founders and found that 10%-24% of their diploid genomes had become lost after about 20 yr of inbreeding (which approximately corresponds to five generations). Lost haplotypes spanned large genomic regions, as expected from the amount of recombination during this limited time period. Altogether, 160,000 SNP alleles became lost from the population, which may include adaptive variants as well as wild-type alleles masking recessively deleterious alleles. Although not sampled, we could indirectly infer that the two male founders had megabase-sized runs of homozygosity and that all three founders showed significant haplotype sharing, meaning that there were on average only 4.2 unique haplotypes in the six copies of each autosome that the founders brought into the population. This violates the assumption of unrelated founder haplotypes often made in conservation and management of endangered species. Our study provides a novel view of how whole-genome resequencing of temporally stratified samples can be used to visualize and directly quantify the consequences of genetic drift in a small inbred population.


Asunto(s)
Lobos , Alelos , Animales , Femenino , Frecuencia de los Genes , Variación Genética , Genética de Población , Haplotipos , Endogamia , Masculino , Lobos/genética
2.
Genome Res ; 30(12): 1727-1739, 2020 12.
Artículo en Inglés | MEDLINE | ID: mdl-33144405

RESUMEN

Changes in interacting cis- and trans-regulatory elements are important candidates for Dobzhansky-Muller hybrid incompatibilities and may contribute to hybrid dysfunction by giving rise to misexpression in hybrids. To gain insight into the molecular mechanisms and determinants of gene expression evolution in natural populations, we analyzed the transcriptome from multiple tissues of two recently diverged Ficedula flycatcher species and their naturally occurring F1 hybrids. Differential gene expression analysis revealed that the extent of differentiation between species and the set of differentially expressed genes varied across tissues. Common to all tissues, a higher proportion of Z-linked genes than autosomal genes showed differential expression, providing evidence for a fast-Z effect. We further found clear signatures of hybrid misexpression in brain, heart, kidney, and liver. However, while testis showed the highest divergence of gene expression among tissues, it showed no clear signature of misexpression in F1 hybrids, even though these hybrids were found to be sterile. It is therefore unlikely that incompatibilities between cis-trans regulatory changes explain the observed sterility. Instead, we found evidence that cis-regulatory changes play a significant role in the evolution of gene expression in testis, which illustrates the tissue-specific nature of cis-regulatory evolution bypassing constraints associated with pleiotropic effects of genes.


Asunto(s)
Proteínas Aviares/genética , Perfilación de la Expresión Génica/métodos , Pájaros Cantores/genética , Testículo/metabolismo , Animales , Encéfalo/metabolismo , Evolución Molecular , Regulación de la Expresión Génica , Riñón/metabolismo , Hígado/metabolismo , Masculino , Miocardio/metabolismo , Especificidad de Órganos , Análisis de Secuencia de ARN , Pájaros Cantores/fisiología , Especificidad de la Especie
3.
Mol Ecol ; 32(7): 1567-1580, 2023 04.
Artículo en Inglés | MEDLINE | ID: mdl-36458895

RESUMEN

When new mutations arise at functional sites they are more likely to impair than improve fitness. If not removed by purifying selection, such deleterious mutations will generate a genetic load that can have negative fitness effects in small populations and increase the risk of extinction. This is relevant for the highly inbred Scandinavian wolf (Canis lupus) population, founded by only three wolves in the 1980s and suffering from inbreeding depression. We used functional annotation and evolutionary conservation scores to study deleterious variation in a total of 209 genomes from both the Scandinavian and neighbouring wolf populations in northern Europe. The masked load (deleterious mutations in heterozygote state) was highest in Russia and Finland with deleterious alleles segregating at lower frequency than neutral variation. Genetic drift in the Scandinavian population led to the loss of ancestral alleles, fixation of deleterious variants and a significant increase in the per-individual realized load (deleterious mutations in homozygote state; an increase by 45% in protein-coding genes) over five generations of inbreeding. Arrival of immigrants gave a temporary genetic rescue effect with ancestral alleles re-entering the population and thereby shifting deleterious alleles from homozygous into heterozygote genotypes. However, in the absence of permanent connectivity to Finnish and Russian populations, inbreeding has then again led to the exposure of deleterious mutations. These observations provide genome-wide insight into the magnitude of genetic load and genetic rescue at the molecular level, and in relation to population history. They emphasize the importance of securing gene flow in the management of endangered populations.


Asunto(s)
Lobos , Animales , Lobos/genética , Carga Genética , Endogamia , Genética de Población , Flujo Genético , Variación Genética
4.
Nat Rev Genet ; 18(2): 87-100, 2017 02.
Artículo en Inglés | MEDLINE | ID: mdl-27840429

RESUMEN

As populations diverge, genetic differences accumulate across the genome. Spurred by rapid developments in sequencing technology, genome-wide population surveys of natural populations promise insights into the evolutionary processes and the genetic basis underlying speciation. Although genomic regions of elevated differentiation are the focus of searches for 'speciation genes', there is an increasing realization that such genomic signatures can also arise by alternative processes that are not related to population divergence, such as linked selection. In this Review, we explore methodological trends in speciation genomic studies, highlight the difficulty in separating processes related to speciation from those emerging from genome-wide properties that are not related to reproductive isolation, and provide a set of suggestions for future work in this area.


Asunto(s)
Evolución Biológica , Flujo Génico , Especiación Genética , Islas Genómicas , Selección Genética/genética , Animales , Variación Genética/genética , Genoma , Genómica , Humanos , Modelos Genéticos
5.
Nat Rev Genet ; 17(7): 422-33, 2016 07.
Artículo en Inglés | MEDLINE | ID: mdl-27265362

RESUMEN

Genetic polymorphism varies among species and within genomes, and has important implications for the evolution and conservation of species. The determinants of this variation have been poorly understood, but population genomic data from a wide range of organisms now make it possible to delineate the underlying evolutionary processes, notably how variation in the effective population size (Ne) governs genetic diversity. Comparative population genomics is on its way to providing a solution to 'Lewontin's paradox' - the discrepancy between the many orders of magnitude of variation in population size and the much narrower distribution of diversity levels. It seems that linked selection plays an important part both in the overall genetic diversity of a species and in the variation in diversity within the genome. Genetic diversity also seems to be predictable from the life history of a species.


Asunto(s)
Evolución Biológica , Variación Genética/genética , Metagenómica , Polimorfismo Genético/genética , Selección Genética/genética , Animales , Humanos
6.
Proc Biol Sci ; 288(1962): 20211066, 2021 11 10.
Artículo en Inglés | MEDLINE | ID: mdl-34727712

RESUMEN

Climate change influences population demography by altering patterns of gene flow and reproductive isolation. Direct mutation rates offer the possibility for accurate dating on the within-species level but are currently only available for a handful of vertebrate species. Here, we use the first directly estimated mutation rate in birds to study the evolutionary history of pied flycatchers (Ficedula hypoleuca). Using a combination of demographic inference and species distribution modelling, we show that all major population splits in this forest-dependent system occurred during periods of increased climate instability and rapid global temperature change. We show that the divergent Spanish subspecies originated during the Eemian-Weichselian transition 115-104 thousand years ago (kya), and not during the last glacial maximum (26.5-19 kya), as previously suggested. The magnitude and rates of climate change during the glacial-interglacial transitions that preceded population splits in pied flycatchers were similar to, or exceeded, those predicted to occur in the course of the current, human-induced climate crisis. As such, our results provide a timely reminder of the strong impact that episodes of climate instability and rapid temperature changes can have on species' evolutionary trajectories, with important implications for the natural world in the Anthropocene.


Asunto(s)
Cambio Climático , Pájaros Cantores , Animales , Biodiversidad , Bosques , Humanos , Pájaros Cantores/genética , Temperatura
7.
Mol Ecol ; 30(16): 3965-3973, 2021 08.
Artículo en Inglés | MEDLINE | ID: mdl-34145933

RESUMEN

Due to its central importance to many aspects of evolutionary biology and population genetics, the long-term effective population size (Ne ) has been estimated for numerous species and populations. However, estimating contemporary Ne is difficult and in practice this parameter is often unknown. In principle, contemporary Ne can be estimated using either analyses of temporal changes in allele frequencies, or the extent of linkage disequilibrium (LD) between unlinked markers. We applied these approaches to estimate contemporary Ne of a relatively recently founded island population of collared flycatchers (Ficedula albicollis). We sequenced the genomes of 85 birds sampled in 1993 and 2015, and applied several temporal methods to estimate Ne at a few thousand (4000-7000). The approach based on LD provided higher estimates of Ne (20,000-32,000) and was associated with high variance, often resulting in infinite Ne . We conclude that whole-genome sequencing data offers new possibilities to estimate high (>1000) contemporary Ne , but also note that such estimates remain challenging, in particular for LD-based methods for contemporary Ne estimation.


Asunto(s)
Pájaros Cantores , Animales , Genética de Población , Genoma , Genómica , Desequilibrio de Ligamiento , Densidad de Población , Pájaros Cantores/genética
8.
Heredity (Edinb) ; 125(1-2): 73-84, 2020 08.
Artículo en Inglés | MEDLINE | ID: mdl-32451423

RESUMEN

Several studies have uncovered a highly heterogeneous landscape of genetic differentiation across the genomes of closely related species. Specifically, genetic differentiation is often concentrated in particular genomic regions ("islands of differentiation") that might contain barrier loci contributing to reproductive isolation, whereas the rest of the genome is homogenized by introgression. Alternatively, linked selection can produce differentiation islands in allopatry without introgression. We explored the influence of introgression on the landscape of genetic differentiation in two hybridizing goose taxa: the Taiga Bean Goose (Anser fabalis) and the Tundra Bean Goose (A. serrirostris). We re-sequenced the whole genomes of 18 individuals (9 of each taxon) and, using a combination of population genomic summary statistics and demographic modeling, we reconstructed the evolutionary history of these birds. Next, we quantified the impact of introgression on the build-up and maintenance of genetic differentiation. We found evidence for a scenario of allopatric divergence (about 2.5 million years ago) followed by recent secondary contact (about 60,000 years ago). Subsequent introgression events led to high levels of gene flow, mainly from the Tundra Bean Goose into the Taiga Bean Goose. This scenario resulted in a largely undifferentiated genomic landscape (genome-wide FST = 0.033) with a few notable differentiation peaks that were scattered across chromosomes. The summary statistics indicated that some peaks might contain barrier loci while others arose in allopatry through linked selection. Finally, based on the low genetic differentiation, considerable morphological variation and incomplete reproductive isolation, we argue that the Taiga and the Tundra Bean Goose should be treated as subspecies.


Asunto(s)
Gansos , Especiación Genética , Hibridación Genética , Animales , Gansos/clasificación , Gansos/genética , Flujo Génico , Aislamiento Reproductivo , Taiga , Tundra
9.
Mol Biol Evol ; 35(10): 2475-2486, 2018 10 01.
Artículo en Inglés | MEDLINE | ID: mdl-30085180

RESUMEN

The rate of recombination impacts on rates of protein evolution for at least two reasons: it affects the efficacy of selection due to linkage and influences sequence evolution through the process of GC-biased gene conversion (gBGC). We studied how recombination, via gBGC, affects inferences of selection in gene sequences using comparative genomic and population genomic data from the collared flycatcher (Ficedula albicollis). We separately analyzed different mutation categories ("strong"-to-"weak," "weak-to-strong," and GC-conservative changes) and found that gBGC impacts on the distribution of fitness effects of new mutations, and leads to that the rate of adaptive evolution and the proportion of adaptive mutations among nonsynonymous substitutions are underestimated by 22-33%. It also biases inferences of demographic history based on the site frequency spectrum. In light of this impact, we suggest that inferences of selection (and demography) in lineages with pronounced gBGC should be based on GC-conservative changes only. Doing so, we estimate that 10% of nonsynonymous mutations are effectively neutral and that 27% of nonsynonymous substitutions have been fixed by positive selection in the flycatcher lineage. We also find that gene expression level, sex-bias in expression, and the number of protein-protein interactions, but not Hill-Robertson interference (HRI), are strong determinants of selective constraint and rate of adaptation of collared flycatcher genes. This study therefore illustrates the importance of disentangling the effects of different evolutionary forces and genetic factors in interpretation of sequence data, and from that infer the role of natural selection in DNA sequence evolution.


Asunto(s)
Evolución Molecular , Conversión Génica , Selección Genética , Pájaros Cantores/genética , Animales , Femenino , Masculino
10.
Genome Res ; 26(9): 1211-8, 2016 09.
Artículo en Inglés | MEDLINE | ID: mdl-27412854

RESUMEN

The fidelity of DNA replication together with repair mechanisms ensure that the genetic material is properly copied from one generation to another. However, on extremely rare occasions when damages to DNA or replication errors are not repaired, germline mutations can be transmitted to the next generation. Because of the rarity of these events, studying the rate at which new mutations arise across organisms has been a great challenge, especially in multicellular nonmodel organisms with large genomes. We sequenced the genomes of 11 birds from a three-generation pedigree of the collared flycatcher (Ficedula albicollis) and used highly stringent bioinformatic criteria for mutation detection and used several procedures to validate mutations, including following the stable inheritance of new mutations to subsequent generations. We identified 55 de novo mutations with a 10-fold enrichment of mutations at CpG sites and with only a modest male mutation bias. The estimated rate of mutation per site per generation was 4.6 × 10(-9), which corresponds to 2.3 × 10(-9) mutations per site per year. Compared to mammals, this is similar to mouse but about half of that reported for humans, which may be due to the higher frequency of male mutations in humans. We confirm that mutation rate scales positively with genome size and that there is a strong negative relationship between mutation rate and effective population size, in line with the drift-barrier hypothesis. Our study illustrates that it should be feasible to obtain direct estimates of the rate of mutation in essentially any organism from which family material can be obtained.


Asunto(s)
Evolución Molecular , Mutación de Línea Germinal/genética , Pájaros Cantores/genética , Animales , Genoma , Secuenciación de Nucleótidos de Alto Rendimiento , Tasa de Mutación , Linaje
11.
Mol Ecol ; 28(9): 2173-2191, 2019 05.
Artículo en Inglés | MEDLINE | ID: mdl-30788868

RESUMEN

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 ≈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.


Asunto(s)
Evolución Biológica , Lobos/genética , Cromosoma Y , Animales , Perros/genética , Especies en Peligro de Extinción , Femenino , Finlandia , Dosificación de Gen , Haplotipos , Masculino , Anotación de Secuencia Molecular , Filogenia , Países Escandinavos y Nórdicos
12.
Mol Ecol ; 28(9): 2290-2304, 2019 05.
Artículo en Inglés | MEDLINE | ID: mdl-30653779

RESUMEN

Detecting positive selection using genomic data is critical to understanding the role of adaptive evolution. Of particular interest in this context is sex chromosomes since they are thought to play a special role in local adaptation and speciation. We sought to circumvent the challenges associated with statistical phasing when using haplotype-based statistics in sweep scans by benefitting from that whole chromosome haplotypes of the sex chromosomes can be obtained by resequencing of individuals of the hemizygous sex. We analyzed whole Z chromosome haplotypes from 100 females from several populations of four black and white flycatcher species (in birds, females are ZW and males ZZ). Based on integrated haplotype score (iHS) and number of segregating sites by length (nSL) statistics, we found strong and frequent haplotype structure in several regions of the Z chromosome in each species. Most of these sweep signals were population-specific, with essentially no evidence for regions under selection shared among species. Some completed sweeps were revealed by the cross-population extended haplotype homozygosity (XP-EHH) statistic. Importantly, by using statistically phased Z chromosome data from resequencing of males, we failed to recover the signals of selection detected in analyses based on whole chromosome haplotypes from females; instead, what likely represent false signals of selection were frequently seen. This highlights the power issues in statistical phasing and cautions against conclusions from selection scans using such data. The detection of frequent selective sweeps on the avian Z chromosome supports a large role of sex chromosomes in adaptive evolution.


Asunto(s)
Adaptación Biológica/genética , Haplotipos , Cromosomas Sexuales , Pájaros Cantores/genética , Animales , Evolución Biológica , Europa (Continente) , Femenino , Genética/estadística & datos numéricos , Masculino , Polimorfismo de Nucleótido Simple , Secuenciación Completa del Genoma
13.
Nat Rev Genet ; 14(2): 83-7, 2013 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-23329110

RESUMEN

Females and males often differ extensively in their physical traits. This sexual dimorphism is largely caused by differences in gene expression. Recent advances in genomics, such as RNA sequencing (RNA-seq), have revealed the nature and extent of sex-biased gene expression in diverse species. Here we highlight new findings regarding the causes of sex-biased expression, including sexual antagonism and incomplete dosage compensation. We also discuss how sex-biased expression can accelerate the evolution of sex-linked genes.


Asunto(s)
Evolución Molecular , Caracteres Sexuales , Animales , Compensación de Dosificación (Genética) , Femenino , Duplicación de Gen , Expresión Génica , Masculino , Cromosomas Sexuales/genética
14.
PLoS Genet ; 12(5): e1006044, 2016 05.
Artículo en Inglés | MEDLINE | ID: mdl-27219623

RESUMEN

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.


Asunto(s)
Intercambio Genético , Recombinación Genética , Pájaros Cantores/genética , Animales , Mapeo Cromosómico , Femenino , Variación Genética , Genoma , Secuenciación de Nucleótidos de Alto Rendimiento , Masculino , Linaje
15.
Genome Res ; 25(11): 1656-65, 2015 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-26355005

RESUMEN

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) and 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.


Asunto(s)
Especiación Genética , Passeriformes/clasificación , Passeriformes/genética , Recombinación Genética , Selección Genética , Animales , Femenino , Flujo Génico , Genética de Población , Genoma , Genómica , Técnicas de Genotipaje , Masculino , Polimorfismo de Nucleótido Simple , Aislamiento Reproductivo , Análisis de Secuencia de ADN , Especificidad de la Especie
16.
Mol Ecol ; 27(1): 99-111, 2018 01.
Artículo en Inglés | MEDLINE | ID: mdl-29171119

RESUMEN

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 1.5-2.5 Mb 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.


Asunto(s)
Genoma , Variación Estructural del Genoma , Retroelementos/genética , Retroviridae/genética , Pájaros Cantores/genética , Animales , Femenino , Masculino , Anotación de Secuencia Molecular , Linaje , Polimorfismo Genético , Polimorfismo de Nucleótido Simple/genética , Especificidad de la Especie
17.
Mol Ecol ; 27(2): 476-492, 2018 01.
Artículo en Inglés | MEDLINE | ID: mdl-29226517

RESUMEN

It is becoming increasingly clear that a significant proportion of the functional sequence within eukaryotic genomes is noncoding. However, since the identification of conserved elements (CEs) has been restricted to a limited number of model organisms, the dynamics and evolutionary character of the genomic landscape of conserved, and hence likely functional, sequence is poorly understood in most species. Moreover, identification and analysis of the full suite of functional sequence are particularly important for the understanding of the genetic basis of trait loci identified in genome scans or quantitative trait locus mapping efforts. We report that ~6.6% of the collared flycatcher genome (74.0 Mb) is spanned by ~1.28 million CEs, a higher proportion of the genome but a lower total amount of conserved sequence than has been reported in mammals. We identified >200,000 CEs specific to either the archosaur, avian, neoavian or passeridan lineages, constituting candidates for lineage-specific adaptations. Importantly, no less than ~71% of CE sites were nonexonic (52.6 Mb), and conserved nonexonic sequence density was negatively correlated with functional exonic density at local genomic scales. Additionally, nucleotide diversity was strongly reduced at nonexonic conserved sites (0.00153) relative to intergenic nonconserved sites (0.00427). By integrating deep transcriptome sequencing and additional genome annotation, we identified novel protein-coding genes, long noncoding RNA genes and transposon-derived (exapted) CEs. The approach taken here based on the use of a progressive cactus whole-genome alignment to identify CEs should be readily applicable to nonmodel organisms in general and help to reveal the rich repertoire of putatively functional noncoding sequence as targets for selection.


Asunto(s)
Secuencia Conservada/genética , Evolución Molecular , Selección Genética , Pájaros Cantores/genética , Animales , Pollos/genética , Mapeo Cromosómico , Exones/genética , Genoma/genética , Genómica , Secuenciación de Nucleótidos de Alto Rendimiento , Mamíferos/genética , Sintenía
18.
Mol Ecol ; 27(18): 3572-3581, 2018 09.
Artículo en Inglés | MEDLINE | ID: mdl-30055065

RESUMEN

Theoretical work suggests that sexual conflict should promote the maintenance of genetic diversity by the opposing directions of selection on males and females. If such conflict is pervasive, it could potentially lead to genomic heterogeneity in levels of genetic diversity an idea that so far has not been empirically tested on a genomewide scale. We used large-scale population genomic and transcriptomic data from the collared flycatcher (Ficedula albicollis) to analyse how sexual conflict, for which we use sex-biased gene expression as a proxy, 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 diversity levels also in intergenic DNA and introns. We find signatures of balancing selection in sex-biased genes but also note that relaxed purifying selection could potentially explain part of the observed patterns. The finding of significant genetic differentiation between males and females for male-biased (and gonad-specific) genes indicates ongoing sexual conflict and sex-specific viability selection, potentially driven by sexual selection. Our results thus indicate that sexual antagonism could potentially be considered as one viable explanation to the long-standing question in evolutionary biology of how genomes can remain so genetically variable in face of strong natural and sexual selection.


Asunto(s)
Variación Genética , Selección Genética , Caracteres Sexuales , Pájaros Cantores/genética , Animales , ADN Intergénico/genética , Femenino , Expresión Génica , Genética de Población , Genoma , Intrones , Masculino , Transcriptoma
19.
PLoS Biol ; 13(8): e1002224, 2015 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-26284513

RESUMEN

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.


Asunto(s)
Aves/genética , Evolución Molecular , Especiación Genética , Variación Genética , Filogenia , Animales , Aves/clasificación , Genoma , Hibridación Genética
20.
Conserv Biol ; 32(6): 1301-1312, 2018 12.
Artículo en Inglés | MEDLINE | ID: mdl-29935028

RESUMEN

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 (Ne ) from 10,000 well before the last glaciation to <500 after this period. Current Ne appeared even lower. The genome-wide FIS 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.


Asunto(s)
Mustelidae , Animales , Conservación de los Recursos Naturales , Genoma , Genómica , Polimorfismo de Nucleótido Simple
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