| 1. |
- Kutschera, Verena E., et al.
(author)
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Purifying Selection in Corvids Is Less Efficient on Islands
- 2020
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In: Molecular biology and evolution. - : OXFORD UNIV PRESS. - 0737-4038 .- 1537-1719. ; 37:2, s. 469-474
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Journal article (peer-reviewed)abstract
- Theory predicts that deleterious mutations accumulate more readily in small populations. As a consequence, mutation load is expected to be elevated in species where life-history strategies and geographic or historical contingencies reduce the number of reproducing individuals. Yet, few studies have empirically tested this prediction using genome-wide data in a comparative framework. We collected whole-genome sequencing data for 147 individuals across seven crow species (Corvus spp.). For each species, we estimated the distribution of fitness effects of deleterious mutations and compared it with proxies of the effective population size N-e. Island species with comparatively smaller geographic range sizes had a significantly increased mutation load. These results support the view that small populations have an elevated risk of mutational meltdown, which may contribute to the higher extinction rates observed in island species.
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| 2. |
- Dussex, Nicolas, et al.
(author)
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A genome-wide investigation of adaptive signatures in protein-coding genes related to tool behaviour in New Caledonian and Hawaiian crows
- 2021
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In: Molecular Ecology. - : John Wiley & Sons. - 0962-1083 .- 1365-294X. ; 30:4, s. 973-986
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Journal article (peer-reviewed)abstract
- Very few animals habitually manufacture and use tools. It has been suggested that advanced tool behaviour co-evolves with a suite of behavioural, morphological and life history traits. In fact, there are indications for such an adaptive complex in tool-using crows (genus Corvus species). Here, we sequenced the genomes of two habitually tool-using and ten non-tool-using crow species to search for genomic signatures associated with a tool-using lifestyle. Using comparative genomic and population genetic approaches, we screened for signals of selection in protein-coding genes in the tool-using New Caledonian and Hawaiian crows. While we detected signals of recent selection in New Caledonian crows near genes associated with bill morphology, our data indicate that genetic changes in these two lineages are surprisingly subtle, with little evidence at present for convergence. We explore the biological explanations for these findings, such as the relative roles of gene regulation and protein-coding changes, as well as the possibility that statistical power to detect selection in recently diverged lineages may have been insufficient. Our study contributes to a growing body of literature aiming to decipher the genetic basis of recently evolved complex behaviour.
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| 3. |
- Rodrigues, Leonor R., et al.
(author)
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The genetic basis and adult reproductive consequences of developmental thermal plasticity
- 2022
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In: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 91:6, s. 1119-1134
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Journal article (peer-reviewed)abstract
- Increasing temperature and thermal variability generate profound selection on populations. Given the fast rate of environmental change, understanding the role of plasticity and genetic adaptation in response to increasing temperatures is critical. This may be especially true for thermal effects on reproductive traits in which thermal fertility limits at high temperatures may be lower than for survival traits. Consequences of changing environments during development on adult phenotypes may be particularly problematic for core traits such as reproduction that begin early in development. Here we examine the consequences of developmental thermal plasticity on subsequent adult reproductive traits and its genetic basis.We used a panel of Drosophila melanogaster (the Drosophila Genetic Reference Panel; DGRP) in which male fertility performance was previously defined as either showing relatively little (status = ‘high’-performing lines) or substantial (‘low’-performing lines) decline when exposed to increasing developmental temperatures. We used a thermal reaction norm approach to quantify variation in the consequences of developmental thermal plasticity on multiple adult reproductive traits, including sex-specific responses, and to identify candidate genes underlying such variation.Developmental thermal stress impacted the means and thermal reaction norms of all reproductive traits except offspring sex ratio. Mating success declined as temperature increased with no difference between high and low lines, whereas increasing temperature resulted in declines for both male and female fertility and productivity but depended on line status. Fertility and offspring number were positively correlated within and between the sexes across lines, but males were more affected than females.We identified 933 SNPs with significant evolved genetic differentiation between high and low lines. In all, 54 of these lie within genomic windows of overall high differentiation, have significant effects of genotype on the male thermal reaction norm for productivity and are associated with 16 genes enriched for phenotypes affecting reproduction, stress responses and autophagy in Drosophila and other organisms.Our results illustrate considerable plasticity in male thermal limits on several reproductive traits following development at high temperature, and we identify differentiated loci with relevant phenotypic effects that may contribute to this population variation. While our work is on a single population, phenotypic results align with an increasing number of studies demonstrating the potential for stronger selection of thermal stress on reproductive traits, particularly in males. Such large fitness costs may have both short- and long-term consequences for the evolution of populations in response to a warming world.
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| 4. |
- Wiberg, R. Axel W., et al.
(author)
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Experimental evolution supports signatures of sexual selection in genomic divergence
- 2021
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In: Evolution Letters. - : Oxford University Press (OUP). - 2056-3744. ; 5:3, s. 214-229
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Journal article (peer-reviewed)abstract
- Comparative genomics has contributed to the growing evidence that sexual selection is an important component of evolutionary divergence and speciation. Divergence by sexual selection is implicated in faster rates of divergence of the X chromosome and of genes thought to underlie sexually selected traits, including genes that are sex biased in expression. However, accurately inferring the relative importance of complex and interacting forms of natural selection, demography, and neutral processes that occurred in the evolutionary past is challenging. Experimental evolution provides an opportunity to apply controlled treatments for multiple generations and examine the consequent genomic divergence. Here, we altered sexual selection intensity, elevating sexual selection in polyandrous lines and eliminating it in monogamous lines, and examined patterns of allele frequency divergence in the genome of Drosophila pseudoobscura after more than 160 generations of experimental evolution. Divergence is not uniform across the genome but concentrated in islands, many of which contain candidate genes implicated in mating behaviors and other sexually selected phenotypes. These are more often seen on the X chromosome, which also shows greater divergence in F-ST than neutral expectations. There are characteristic signatures of selection seen in these regions, with lower diversity on the X chromosome than the autosomes, and differences in diversity on the autosomes between selection regimes. Reduced Tajima's D within some of the divergent regions may imply that selective sweeps have occurred, despite considerable recombination. These changes are associated with both differential gene expression between the lines and sex-biased gene expression within the lines. Our results are very similar to those thought to implicate sexual selection in divergence between species and natural populations, and hence provide experimental support for the likely role of sexual selection in driving such types of genetic divergence, but also illustrate how variable outcomes can be for different genomic regions.
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| 5. |
- Immonen, Elina, et al.
(author)
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Experimental Life History Evolution Results in Sex-specific Evolution of Gene Expression in Seed Beetles
- 2023
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In: Genome Biology and Evolution. - : Oxford University Press. - 1759-6653. ; 15:1
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Journal article (peer-reviewed)abstract
- The patterns of reproductive timing and senescence vary within and across species owing to differences in reproductive strategies, but our understanding of the molecular underpinnings of such variation is incomplete. This is perhaps particularly true for sex differences. We investigated the evolution of sex-specific gene expression associated with life history divergence in replicated populations of the seed beetle Acanthoscelides obtectus, experimentally evolving under (E)arly or (L)ate life reproduction for >200 generations which has resulted in strongly divergent life histories. We detected 1,646 genes that were differentially expressed in E and L lines, consistent with a highly polygenic basis of life history evolution. Only 30% of differentially expressed genes were similarly affected in males and females. The evolution of long life was associated with significantly reduced sex differences in expression, especially in non-reproductive tissues. The expression differences were overall more pronounced in females, in accordance with their greater phenotypic divergence in lifespan. Functional enrichment analysis revealed differences between E and L beetles in gene categories previously implicated in aging, such as mitochondrial function and defense response. The results show that divergent life history evolution can be associated with profound changes in gene expression that alter the transcriptome in a sex-specific way, highlighting the importance of understanding the mechanisms of aging in each sex.
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| 6. |
- Kaufmann, Philipp, 1991-, et al.
(author)
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Assembly of polymorphic Y chromosomes reveals molecular basis of variation in male body size
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Other publication (other academic/artistic)abstract
- The Y chromosome of males is theorized to facilitate the evolution of sexual dimorphism by accumulating sexually antagonistic loci, but empirical support is limited. In the seed beetle Callosobruchus maculatus, variation in sexually antagonistic body size is linked to at least two segregating Y haplotypes in males that facilitated rapid laboratory evolution of sexual size dimorphism. Here we assemble previously uncharacterized C. maculatus sex chromosome sequences and identify molecular differences between the two predicted Y haplotypes. The Y chromosome of C. maculatus shows typical hallmarks of degeneration: it is ampliconic and approximately 80% smaller than the X. Nevertheless, the Y harbors over 400 genes with a mixed autosomal and X chromosome ancestry that are enriched with metabolic, developmental and gene regulatory functions. Crucially, we find that besides an autosomal copy of the gene target of rapamycin (TOR), males carry an additional TOR copy on the Y chromosome. TOR is a conserved regulator of growth across taxa, and a Y-linked copy of TOR thus provides a male specific opportunity to alter body size. The two identified Y haplotypes show fixed single nucleotide differences in or in close proximity to over 100 genes, but also copy number variation for TOR, where the more frequent (~95%) Y haplotype that causes increased sexual size dimorphism has two additional TOR copies. These results suggest that part of the sexual conflict over body size has been mitigated by autosome to Y translocation of TOR followed by gene duplications that further increased sexual dimorphism.
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| 7. |
- Kaufmann, Philipp, et al.
(author)
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Y-Linked Copy Number Polymorphism of Target of Rapamycin Is Associated with Sexual Size Dimorphism in Seed Beetles
- 2023
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In: Molecular biology and evolution. - : Oxford University Press. - 0737-4038 .- 1537-1719. ; 40:8
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Journal article (peer-reviewed)abstract
- The Y chromosome is theorized to facilitate evolution of sexual dimorphism by accumulating sexually antagonistic loci, but empirical support is scarce. Due to the lack of recombination, Y chromosomes are prone to degenerative processes, which poses a constraint on their adaptive potential. Yet, in the seed beetle, Callosobruchus maculatus segregating Y linked variation affects male body size and thereby sexual size dimorphism (SSD). Here, we assemble C. maculatus sex chromosome sequences and identify molecular differences associated with Y-linked SSD variation. The assembled Y chromosome is largely euchromatic and contains over 400 genes, many of which are ampliconic with a mixed autosomal and X chromosome ancestry. Functional annotation suggests that the Y chromosome plays important roles in males beyond primary reproductive functions. Crucially, we find that, besides an autosomal copy of the gene target of rapamycin (TOR), males carry an additional TOR copy on the Y chromosome. TOR is a conserved regulator of growth across taxa, and our results suggest that a Y-linked TOR provides a male specific opportunity to alter body size. A comparison of Y haplotypes associated with male size difference uncovers a copy number variation for TOR, where the haplotype associated with decreased male size, and thereby increased sexual dimorphism, has two additional TOR copies. This suggests that sexual conflict over growth has been mitigated by autosome to Y translocation of TOR followed by gene duplications. Our results reveal that despite of suppressed recombination, the Y chromosome can harbor adaptive potential as a male-limited supergene.
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| 8. |
- Wiberg, R. Axel W., et al.
(author)
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Mating strategy predicts gene presence/absence patterns in a genus of simultaneously hermaphroditic flatworms
- 2022
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In: Evolution. - : John Wiley & Sons. - 0014-3820 .- 1558-5646. ; 76:12, s. 3054-3066
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Journal article (peer-reviewed)abstract
- Gene repertoire turnover is a characteristic of genome evolution. However, we lack well-replicated analyses of presence/absence patterns associated with different selection contexts. Here, we study similar to 100 transcriptome assemblies across Macrostomum, a genus of simultaneously hermaphroditic flatworms exhibiting multiple convergent shifts in mating strategy and associated reproductive morphologies. Many species mate reciprocally, with partners donating and receiving sperm at the same time. Other species convergently evolved to mate by hypodermic injection of sperm into the partner. We find that for orthologous transcripts annotated as expressed in the body region containing the testes, sequences from hypodermically inseminating species diverge more rapidly from the model species, Macrostomum lignano, and have a lower probability of being observed in other species. For other annotation categories, simpler models with a constant rate of similarity decay with increasing genetic distance from M. lignano match the observed patterns well. Thus, faster rates of sequence evolution for hypodermically inseminating species in testis-region genes result in higher rates of homology detection failure, yielding a signal of rapid evolution in sequence presence/absence patterns. Our results highlight the utility of considering appropriate null models for unobserved genes, as well as associating patterns of gene presence/absence with replicated evolutionary events in a phylogenetic context.
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