| 1. |
- Almén, Markus Sällman, et al.
(författare)
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Adaptive radiation of Darwin's finches revisited using whole genome sequencing
- 2016
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Ingår i: Bioessays. - : Wiley. - 0265-9247 .- 1521-1878. ; 38:1, s. 14-20
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Tidskriftsartikel (refereegranskat)abstract
- We recently used genome sequencing to study the evolutionary history of the Darwin's finches. A prominent feature of our data was that different polymorphic sites in the genome tended to indicate different genetic relationships among these closely related species. Such patterns are expected in recently diverged genomes as a result of incomplete lineage sorting. However, we uncovered conclusive evidence that these patterns have also been influenced by interspecies hybridisation, a process that has likely played an important role in the radiation of Darwin's finches. A major discovery was that segregation of two haplotypes at the ALX1 locus underlies variation in beak shape among the Darwin's finches, and that differences between the two haplotypes in a 240 kb region in blunt and pointed beaked birds involve both coding and regulatory changes. As we review herein, the evolution of such adaptive haplotypes comprising multiple causal changes appears to be an important mechanism contributing to the evolution of biodiversity.
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| 2. |
- Antonelli, Alexandre, 1978, et al.
(författare)
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Embracing heterogeneity: Coalescing the tree of life and the future of phylogenomics
- 2019
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Ingår i: PeerJ. - : PeerJ. - 2167-8359. ; 2019:2
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Tidskriftsartikel (refereegranskat)abstract
- Building the Tree of Life (ToL) is a major challenge of modern biology, requiring advances in cyberinfrastructure, data collection, theory, and more. Here, we argue that phylogenomics stands to benefit by embracing the many heterogeneous genomic signals emerging from the first decade of large-scale phylogenetic analysis spawned by high-throughput sequencing (HTS). Such signals include those most commonly encountered in phylogenomic datasets, such as incomplete lineage sorting, but also those reticulate processes emerging with greater frequency, such as recombination and introgression. Here we focus specifically on how phylogenetic methods can accommodate the heterogeneity incurred by such population genetic processes; we do not discuss phylogenetic methods that ignore such processes, such as concatenation or supermatrix approaches or supertrees. We suggest that methods of data acquisition and the types of markers used in phylogenomics will remain restricted until a posteriori methods of marker choice are made possible with routine whole-genome sequencing of taxa of interest. We discuss limitations and potential extensions of a model supporting innovation in phylogenomics today, the multispecies coalescent model (MSC). Macroevolutionary models that use phylogenies, such as character mapping, often ignore the heterogeneity on which building phylogenies increasingly rely and suggest that assimilating such heterogeneity is an important goal moving forward. Finally, we argue that an integrative cyberinfrastructure linking all steps of the process of building the ToL, from specimen acquisition in the field to publication and tracking of phylogenomic data, as well as a culture that values contributors at each step, are essential for progress.
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| 3. |
- Feng, Chungang, et al.
(författare)
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Moderate nucleotide diversity in the Atlantic herring is associated with a low mutation rate
- 2017
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Ingår i: eLIFE. - : ELIFE SCIENCES PUBLICATIONS LTD. - 2050-084X. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- The Atlantic herring is one of the most abundant vertebrates on earth but its nucleotide diversity is moderate (pi = 0.3%), only three-fold higher than in human. Here, we present a pedigree-based estimation of the mutation rate in this species. Based on whole-genome sequencing of four parents and 12 offspring, the estimated mutation rate is 2.0 x 10(-9) per base per generation. We observed a high degree of parental mosaicism indicating that a large fraction of these de novo mutations occurred during early germ cell development. The estimated mutation rate the lowest among vertebrates analyzed to date - partially explains the discrepancy between the rather low nucleotide diversity in herring and its huge census population size. But a species like the herring will never reach its expected nucleotide diversity because of fluctuations in population size over the millions of years it takes to build up high nucleotide diversity.
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| 4. |
- Han, Fan, et al.
(författare)
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Gene flow, ancient polymorphism, and ecological adaptation shape the genomic landscape of divergence among Darwin's finches
- 2017
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Ingår i: Genome Research. - : Cold Spring Harbor Laboratory. - 1088-9051 .- 1549-5469. ; 27:6, s. 1004-1015
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Tidskriftsartikel (refereegranskat)abstract
- Genomic comparisons of closely related species have identified "islands" of locally elevated sequence divergence. Genomic islands may contain functional variants involved in local adaptation or reproductive isolation and may therefore play an important role in the speciation process. However, genomic islands can also arise through evolutionary processes unrelated to speciation, and examination of their properties can illuminate how new species evolve. Here, we performed scans for regions of high relative divergence (FST) in 12 species pairs of Darwin's finches at different genetic distances. In each pair, we identify genomic islands that are, on average, elevated in both relative divergence (FST) and absolute divergence (dXY). This signal indicates that haplotypes within these genomic regions became isolated from each other earlier than the rest of the genome. Interestingly, similar numbers of genomic islands of elevated dXY are observed in sympatric and allopatric species pairs, suggesting that recent gene flow is not a major factor in their formation. We find that two of the most pronounced genomic islands contain the ALX1 and HMGA2 loci, which are associated with variation in beak shape and size, respectively, suggesting that they are involved in ecological adaptation. A subset of genomic island regions, including these loci, appears to represent anciently diverged haplotypes that evolved early during the radiation of Darwin's finches. Comparative genomics data indicate that these loci, and genomic islands in general, have exceptionally low recombination rates, which may play a role in their establishment.
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| 5. |
- Hill, Jason, et al.
(författare)
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Low Mutation Load in a Supergene Underpinning Alternative Male Mating Strategies in Ruff (Calidris pugnax)
- 2023
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Ingår i: Molecular biology and evolution. - : Oxford University Press. - 0737-4038 .- 1537-1719. ; 40:12
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Tidskriftsartikel (refereegranskat)abstract
- A paradox in evolutionary biology is how supergenes can maintain high fitness despite reduced effective population size, the suppression of recombination, and the expected accumulation of mutational load. The ruff supergene involves 2 rare inversion haplotypes (satellite and faeder). These are recessive lethals but with dominant effects on male mating strategies, plumage, and body size. Sequence divergence to the wild-type (independent) haplotype indicates that the inversion could be as old as 4 million years. Here, we have constructed a highly contiguous genome assembly of the inversion region for both the independent and satellite haplotypes. Based on the new data, we estimate that the recombination event(s) creating the satellite haplotype occurred only about 70,000 yr ago. Contrary to expectations for supergenes, we find no substantial expansion of repeats and only a modest mutation load on the satellite and faeder haplotypes despite high sequence divergence to the non-inverted haplotype (1.46%). The essential centromere protein N (CENPN) gene is disrupted by the inversion and is as well conserved on the inversion haplotypes as on the noninversion haplotype. These results suggest that the inversion may be much younger than previously thought. The low mutation load, despite recessive lethality, may be explained by the introgression of the inversion from a now extinct lineage.
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| 6. |
- Lamichhaney, Sangeet, 1984-, et al.
(författare)
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A beak size locus in Darwin’s finches facilitated character displacement during a drought
- 2016
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 352:6284, s. 470-474
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Tidskriftsartikel (refereegranskat)abstract
- Ecological character displacement is a process of morphological divergence that reducescompetition for limited resources. We used genomic analysis to investigate the geneticbasis of a documented character displacement event in Darwin’s finches on Daphne Majorin the Galápagos Islands: The medium ground finch diverged from its competitor, the largeground finch, during a severe drought. We discovered a genomic region containing theHMGA2gene that varies systematically among Darwin’s finch species with different beaksizes. Two haplotypes that diverged early in the radiation were involved in the characterdisplacement event: Genotypes associated with large beak size were at a strong selectivedisadvantage in medium ground finches (selection coefficients= 0.59). Thus, a majorlocus has apparently facilitated a rapid ecological diversification in the adaptive radiationof Darwin’s finches.
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| 7. |
- Lamichhaney, Sangeet, et al.
(författare)
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A comparison of the association between large haplotype blocks under selection and the presence/absence of inversions
- 2019
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Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 9:8, s. 4888-4896
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Tidskriftsartikel (refereegranskat)abstract
- Inversions may contribute to ecological adaptation and phenotypic diversity, and with the advent of second and third generation sequencing technologies, the ability to detect inversion polymorphisms has been enhanced dramatically. A key molecular consequence of an inversion is the suppression of recombination allowing independent accumulation of genetic changes between alleles over time. This may lead to the development of divergent haplotype blocks maintained by balancing selection. Thus, divergent haplotype blocks are often considered as indicating the presence of an inversion. In this paper, we first review the features of a 7.7Mb inversion causing the Rose-comb phenotype in chicken, as a model for how inversions evolve and directly affect phenotypes. Second, we compare the genetic basis for alternative mating strategies in ruff and timing of reproduction in Atlantic herring, both associated with divergent haplotype blocks. Alternative male mating strategies in ruff are associated with a 4.5Mb inversion that occurred about 4 million years ago. In fact, the ruff inversion shares some striking features with the Rose-comb inversion such as disruption of a gene at one of the inversion breakpoints and generation of a new allele by recombination between the inverted and noninverted alleles. In contrast, inversions do not appear to be a major reason for the fairly large haplotype blocks (range 10-200kb) associated with ecological adaptation in the herring. Thus, it is important to note that divergent haplotypes may also be maintained by natural selection in the absence of structural variation.
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| 8. |
- Lamichhaney, Sangeet, et al.
(författare)
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Evolution of Darwin's finches and their beaks revealed by genome sequencing
- 2015
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 518:7539
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Tidskriftsartikel (refereegranskat)abstract
- Darwin's finches, inhabiting the Galapagos archipelago and Cocos Island, constitute an iconic model for studies of speciation and adaptive evolution. Here we report the results of whole-genome re-sequencing of 120 individuals representing all of the Darwin's finch species and two close relatives' Phylogenetic analysis reveals important discrepancies with the phenotype-based taxonomy. We find extensive evidence for interspecific gene flow throughout the radiation. Hybridization has given rise to species of mixed ancestry. A 240 kilobase haplotype encompassing the ALX1 gene that encodes a transcription factor affecting craniofacial. development is strongly associated with beak shape diversity across Darwin's finch species as well as within the medium ground finch (Geospiza fortis) a species that has undergone rapid evolution of beak shape in response to environmental changes. The ALX1 haplotype has contributed to diversification of beak shapes among the Darwin's finches and thereby, to an expanded utilization of food resources.
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| 9. |
- Lamichhaney, Sangeet, 1984-, et al.
(författare)
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Female-biased gene flow between two species of Darwin’s finches
- 2020
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Ingår i: Nature Ecology & Evolution. - : Springer Science and Business Media LLC. - 2397-334X. ; 4:7, s. 979-986
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Tidskriftsartikel (refereegranskat)abstract
- The mosaic nature of hybrid genomes is well recognized, but little is known of how they are shaped initially by patterns of breeding, selection, recombination and differential incompatibilities. On the small Galápagos island of Daphne Major two species of Darwin’s finches, Geospiza fortis and G. scandens, hybridize rarely and backcross bidirectionally with little or no loss of fitness under conditions of plentiful food. We used whole genome sequences to compare genomes from periods before and after successful interbreeding followed by backcrossing. We inferred extensive introgression from G. fortis to G. scandens on autosomes and mitochondria but not on the Z chromosome. The unique combination of long-term field observations and genomic data shows that the reduction of gene flow for Z-linked loci reflects female-biased gene flow, arising from hybrid male disadvantage in competition for territories and mates, rather than from genetic incompatibilities at Z-linked loci.
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| 10. |
- Lamichhaney, Sangeet, 1984-, et al.
(författare)
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Parallel adaptive evolution of geographically distant herring populations on both sides of the North Atlantic Ocean
- 2017
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : NATL ACAD SCIENCES. - 0027-8424 .- 1091-6490. ; 114:17, s. E3452-E3461
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Tidskriftsartikel (refereegranskat)abstract
- Atlantic herring is an excellent species for studying the genetic basis of adaptation in geographically distant populations because of its characteristically large population sizes and low genetic drift. In this study we compared whole-genome resequencing data of Atlantic herring populations from both sides of the Atlantic Ocean. An important finding was the very low degree of genetic differentiation among geographically distant populations (fixation index = 0.026), suggesting lack of reproductive isolation across the ocean. This feature of the Atlantic herring facilitates the detection of genetic factors affecting adaptation because of the sharp contrast between loci showing genetic differentiation resulting from natural selection and the low background noise resulting from genetic drift. We show that genetic factors associated with timing of reproduction are shared between genetically distinct and geographically distant populations. The genes for thyroid-stimulating hormone receptor (TSHR), the SOX11 transcription factor (SOX11), calmodulin (CALM), and estrogen receptor 2 (ESR2A), all with a significant role in reproductive biology, were among the loci that showed the most consistent association with spawning time throughout the species range. In fact, the same two SNPs located at the 5' end of TSHR showed the most significant association with spawning time in both the east and west Atlantic. We also identified unexpected haplotype sharing between spring-spawning oceanic herring and autumn-spawning populations across the Atlantic Ocean and the Baltic Sea. The genomic regions showing this pattern are unlikely to control spawning time but may be involved in adaptation to ecological factor(s) shared among these populations.
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