| 1. |
- Arnegard, Matthew E., et al.
(author)
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Genetics of ecological divergence during speciation
- 2014
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 511:7509, s. 307-311
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Journal article (peer-reviewed)abstract
- Ecological differences often evolve early in speciation as divergent natural selection drives adaptation to distinct ecological niches, leading ultimately to reproductive isolation. Although this process is a major generator of biodiversity, its genetic basis is still poorly understood. Here we investigate the genetic architecture of niche differentiation in a sympatric species pair of threespine stickleback fish by mapping the environment-dependent effects of phenotypic traits on hybrid feeding and performance under semi-natural conditions. We show that multiple, unlinked loci act largely additively to determine position along the major niche axis separating these recently diverged species. We also find that functional mismatch between phenotypic traits reduces the growth of some stickleback hybrids beyond that expected from an intermediate phenotype, suggesting a role for epistasis between the underlying genes. This functional mismatch might lead to hybrid incompatibilities that are analogous to those underlying intrinsic reproductive isolation but depend on the ecological context.
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| 2. |
- Jones, Felicity C., et al.
(author)
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The genomic basis of adaptive evolution in threespine sticklebacks
- 2012
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 484:7392, s. 55-61
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Journal article (peer-reviewed)abstract
- Marine stickleback fish have colonized and adapted to thousands of streams and lakes formed since the last ice age, providing an exceptional opportunity to characterize genomic mechanisms underlying repeated ecological adaptation in nature. Here we develop a high-quality reference genome assembly for threespine sticklebacks. By sequencing the genomes of twenty additional individuals from a global set of marine and freshwater populations, we identify a genome-wide set of loci that are consistently associated with marine-freshwater divergence. Our results indicate that reuse of globally shared standing genetic variation, including chromosomal inversions, has an important role in repeated evolution of distinct marine and freshwater sticklebacks, and in the maintenance of divergent ecotypes during early stages of reproductive isolation. Both coding and regulatory changes occur in the set of loci underlying marine-freshwater evolution, but regulatory changes appear to predominate in this well known example of repeated adaptive evolution in nature.
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| 3. |
- Martin Cerezo, Maria Luisa, et al.
(author)
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Identification and quantification of chimeric sequencing reads in a highly multiplexed RAD-seq protocol
- 2022
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In: Molecular Ecology Resources. - : Wiley. - 1755-098X .- 1755-0998. ; 22:8, s. 2860-2870
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Journal article (peer-reviewed)abstract
- Highly multiplexed approaches have become common in genomic studies. They have improved the cost-effectiveness of genotyping hundreds of individuals using combinatorially barcoded adapters. These strategies, however, can potentially misassigned reads to incorrect samples. Here, we used a modified quaddRAD protocol to analyse the occurrence of index hopping and PCR chimeras in a series of experiments with up to 100 multiplexed samples per sequencing lane (639 samples in total). We created two types of sequencing libraries: four libraries of type A, where PCRs were run on individual samples before multiplexing, and three libraries of type B, where PCRs were run on pooled samples. We used fixed pairs of inner barcodes to identify chimeric reads. Type B libraries show a higher percentage of misassigned reads (1.15%) than type A libraries (0.65%). We also quantify the commonly undetectable chimeric sequences that occur whenever multiplexed groups of samples with different outer barcodes are sequenced together on a single flow cell. Our results suggest that these types of chimeric sequences represent up to 1.56% and 1.29% of reads in type A and B libraries, respectively. We also show that increasing the number of mismatches allowed for barcode rescue to above 2 dramatically increases the number of recovered chimeric reads. We provide recommendations for developing highly multiplexed RAD-seq protocols and analysing the resulting data to minimize the generation of chimeric sequences, allowing their quantification and a finer control on the number of PCR cycles necessary to generate enough input DNA for library preparation.
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| 4. |
- Martin Cerezo, Maria Luisa, et al.
(author)
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Population structure of Apodemus flavicollis and comparison to Apodemus sylvaticus in northern Poland based on RAD-seq
- 2020
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In: BMC Genomics. - : BMC. - 1471-2164. ; 21:1
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Journal article (peer-reviewed)abstract
- Background Mice of the genus Apodemus are one the most common mammals in the Palaearctic region. Despite their broad range and long history of ecological observations, there are no whole-genome data available for Apodemus, hindering our ability to further exploit the genus in evolutionary and ecological genomics context. Results Here we present results from the double-digest restriction site-associated DNA sequencing (ddRAD-seq) on 72 individuals of A. flavicollis and 10 A. sylvaticus from four populations, sampled across 500 km distance in northern Poland. Our data present clear genetic divergence of the two species, with average p-distance, based on 21377 common loci, of 1.51% and a mutation rate of 0.0011 - 0.0019 substitutions per site per million years. We provide a catalogue of 117 highly divergent loci that enable genetic differentiation of the two species in Poland and to a large degree of 20 unrelated samples from several European countries and Tunisia. We also show evidence of admixture between the three A. flavicollis populations but demonstrate that they have negligible average population structure, with largest pairwise F(ST)Conclusion Our study demonstrates the feasibility of ddRAD-seq in Apodemus and provides the first insights into the population genomics of the species.
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| 5. |
- Shipilina, Daria, et al.
(author)
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On the origin and structure of haplotype blocks
- 2023
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In: Molecular Ecology. - : John Wiley & Sons. - 0962-1083 .- 1365-294X. ; 32:6, s. 1441-1457
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Journal article (peer-reviewed)abstract
- The term "haplotype block " is commonly used in the developing field of haplotype-based inference methods. We argue that the term should be defined based on the structure of the Ancestral Recombination Graph (ARG), which contains complete information on the ancestry of a sample. We use simulated examples to demonstrate key features of the relationship between haplotype blocks and ancestral structure, emphasizing the stochasticity of the processes that generate them. Even the simplest cases of neutrality or of a "hard " selective sweep produce a rich structure, often missed by commonly used statistics. We highlight a number of novel methods for inferring haplotype structure, based on the full ARG, or on a sequence of trees, and illustrate how they can be used to define haplotype blocks using an empirical data set. While the advent of new, computationally efficient methods makes it possible to apply these concepts broadly, they (and additional new methods) could benefit from adding features to explore haplotype blocks, as we define them. Understanding and applying the concept of the haplotype block will be essential to fully exploit long and linked-read sequencing technologies.
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