| 1. |
- Boman, Jesper, et al.
(författare)
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Environmental stress during larval development induces DNA methylation shifts in the migratory painted lady butterfly (Vanessa cardui)
- 2023
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Ingår i: Molecular Ecology. - : John Wiley & Sons. - 0962-1083 .- 1365-294X. ; 32:13, s. 3513-3523
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Tidskriftsartikel (refereegranskat)abstract
- Seasonal environmental fluctuations provide formidable challenges for living organisms, especially small ectotherms such as butterflies. A common strategy to cope with harsh environments is to enter diapause, but some species avoid unsuitable conditions by migrating. Despite a growing understanding of migration in the life cycles of some butterfly species, it remains unknown how individuals register and store environmental cues to determine whether and where to migrate. Here, we explored how competition and host plant availability during larval development affect patterns of DNA methylation in the migratory painted lady (Vanessa cardui) butterfly. We identify a set of potentially functional methylome shifts associated with differences in the environment, indicating that DNA methylation is involved in the response to different conditions during larval development. By analysing the transcriptome for the same samples used for methylation profiling, we also uncovered a non-monotonic relationship between gene body methylation and gene expression. Our results provide a starting point for understanding the interplay between DNA methylation and gene expression in butterflies in general and how differences in environmental conditions during development can trigger unique epigenetic marks that might be important for behavioural decisions in the adult stage.
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| 2. |
- Boman, Jesper, et al.
(författare)
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Evolution of hybrid inviability associated with chromosome fusions
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Chromosomal rearrangements, such as inversions, have received considerable attention in the speciation literature due to their hampering effects on recombination. However, less is known about how other rearrangements, such as chromosome fissions and fusions, can affect the evolution of reproductive isolation. Here, we used crosses between populations of the wood white butterfly (Leptidea sinapis) with different karyotypes to identify genomic regions associated with hybrid inviability. We mapped candidate loci for hybrid inviability by contrasting allele frequencies between F2 hybrids that survived until the adult stage with individuals of the same cohort that succumbed to hybrid incompatibilities. Hybrid inviability factors were predominantly found in fast-evolving regions with reduced recombination rates, especially in regions where chromosome fusions have occurred. By analyzing sequencing coverage, we excluded aneuploidies as a direct link between hybrid inviability and chromosome fusions. Instead, our results point to an indirect relationship between hybrid inviability and chromosome fusions, possibly related to reductions in recombination rate caused by fusions. These results highlight that the extensive variation in chromosome numbers observed across the tree of life does not only distinguish species but can also be involved in speciation by being hotspots for the early evolution of postzygotic reproductive isolation.
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| 3. |
- Boman, Jesper, et al.
(författare)
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Larger genomes show improved buffering of adult fitness against environmental stress in seed beetles
- 2023
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Ingår i: Biology Letters. - : Royal Society. - 1744-9561 .- 1744-957X. ; 19:1
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Tidskriftsartikel (refereegranskat)abstract
- Our general understanding of the evolution of genome size (GS) is incomplete, and it has long been clear that GS does not reflect organismal complexity. Here, we assess the hypothesis that larger genomes may allow organisms to better cope with environmental variation. It is, for example, possible that genome expansion due to proliferation of transposable elements or gene duplications may affect the ability to regulate and fine-tune transcriptional profiles. We used 18 populations of the seed beetle Callosobruchus maculatus, which differ in GS by up to 4.5%, and exposed adults and juveniles to environmental stress in a series of experiments where stage-specific fitness was assayed. We found that populations with larger genomes were indeed better buffered against environmental stress for adult, but not for juvenile, fitness. The genetic correlation across populations between GS and canalization of adult fitness is consistent with a role for natural selection in the evolution of GS.
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| 4. |
- Boman, Jesper, et al.
(författare)
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Meiotic drive against chromosome fusions in butterfly hybrids
- 2024
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Ingår i: Chromosome Research. - : Springer. - 0967-3849 .- 1573-6849. ; 32:2
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Tidskriftsartikel (refereegranskat)abstract
- Species frequently differ in the number and structure of chromosomes they harbor, but individuals that are heterozygous for chromosomal rearrangements may suffer from reduced fitness. Chromosomal rearrangements like fissions and fusions can hence serve as a mechanism for speciation between incipient lineages, but their evolution poses a paradox. How can rearrangements get fixed between populations if heterozygotes have reduced fitness? One solution is that this process predominantly occurs in small and isolated populations, where genetic drift can override natural selection. However, fixation is also more likely if a novel rearrangement is favored by a transmission bias, such as meiotic drive. Here, we investigate chromosomal transmission distortion in hybrids between two wood white (Leptidea sinapis) butterfly populations with extensive karyotype differences. Using data from two different crossing experiments, we uncover that there is a transmission bias favoring the ancestral chromosomal state for derived fusions, a result that shows that chromosome fusions actually can fix in populations despite being counteracted by meiotic drive. This means that meiotic drive not only can promote runaway chromosome number evolution and speciation, but also that it can be a conservative force acting against karyotypic change and the evolution of reproductive isolation. Based on our results, we suggest a mechanistic model for why chromosome fusion mutations may be opposed by meiotic drive and discuss factors contributing to karyotype evolution in Lepidoptera.
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| 5. |
- Boman, Jesper, et al.
(författare)
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On the origin of an insular hybrid butterfly species
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Most species arise from the divergence of two populations within a species, but this is not only way speciation can occur. A new species can also evolve when diverging lineages hybridize and give rise to a persistent and ecologically differentiated species. Hybrid speciation in animals has been intensely debated, partly because hard evidence for the process have been difficult to gain. Recent access to large-scale, whole-genome sequencing data and development of novel analytical methods have made it more feasible to statistically test for hybrid origin of lineages. Here we report the discovery of a hybrid butterfly lineage. This lineage is mainly inhabiting an island in the Baltic Sea in Northern Europe and was previously described as a subspecies (horkei) of one of the parental species (Aricia artaxerxes). By analyzing whole-genome resequencing data, we conclude that horkei originated as a consequence of hybridization between A. artaxerxes and A. agestis. We show that this hybridization event occurred approximately 54,000 years ago, predating the last glaciation of the current distribution range. Horkei must therefore have persisted long enough to be able to colonize its current distribution range, despite that this range lies between the current ranges of the parental species. The hybrid origin, the maintenance of genomic integrity through time periods with dramatic climatic changes and the expression of a combination of parental traits - such as voltinism and host plant use - suggest that horkei can be considered a distinct species (Aricia horkei stat. nov.). Thus, we add to a growing list of hybrid speciation cases in animals.
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| 6. |
- Boman, Jesper, et al.
(författare)
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Regulatory and evolutionary impact of DNA methylation in two songbird species and their naturally occurring F1 hybrids
- 2024
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Ingår i: BMC Biology. - : BioMed Central (BMC). - 1741-7007. ; 22:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Regulation of transcription by DNA methylation in 5'-CpG-3' context is a widespread mechanism allowing differential expression of genetically identical cells to persist throughout development. Consequently, differences in DNA methylation can reinforce variation in gene expression among cells, tissues, populations, and species. Despite a surge in studies on DNA methylation, we know little about the importance of DNA methylation in population differentiation and speciation. Here we investigate the regulatory and evolutionary impact of DNA methylation in five tissues of two Ficedula flycatcher species and their naturally occurring F-1 hybrids.Results: We show that the density of CpG in the promoters of genes determines the strength of the association between DNA methylation and gene expression. The impact of DNA methylation on gene expression varies among tissues with the brain showing unique patterns. Differentially expressed genes between parental species are predicted by genetic and methylation differentiation in CpG-rich promoters. However, both these factors fail to predict hybrid misexpression suggesting that promoter mismethylation is not a main determinant of hybrid misexpression in Ficedula flycatchers. Using allele-specific methylation estimates in hybrids, we also determine the genome-wide contribution of cis- and trans effects in DNA methylation differentiation. These distinct mechanisms are roughly balanced in all tissues except the brain, where trans differences predominate.Conclusions: Overall, this study provides insight on the regulatory and evolutionary impact of DNA methylation in songbirds.
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| 7. |
- Boman, Jesper, et al.
(författare)
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The Effects of GC-Biased Gene Conversion on Patterns of Genetic Diversity among and across Butterfly Genomes
- 2021
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Ingår i: Genome Biology and Evolution. - : Oxford University Press. - 1759-6653. ; 13:5
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Tidskriftsartikel (refereegranskat)abstract
- Recombination reshuffles the alleles of a population through crossover and gene conversion. These mechanisms have considerable consequences on the evolution and maintenance of genetic diversity. Crossover, for example, can increase genetic diversity by breaking the linkage between selected and nearby neutral variants. Bias in favor of G or C alleles during gene conversion may instead promote the fixation of one allele over the other, thus decreasing diversity. Mutation bias from G or C to A and T opposes GC-biased gene conversion (gBGC). Less recognized is that these two processes may-when balanced-promote genetic diversity. Here, we investigate how gBGC and mutation bias shape genetic diversity patterns in wood white butterflies (Leptidea sp.). This constitutes the first in-depth investigation of gBGC in butterflies. Using 60 resequenced genomes from six populations of three species, we find substantial variation in the strength of gBGC across lineages. When modeling the balance of gBGC and mutation bias and comparing analytical results with empirical data, we reject gBGC as the main determinant of genetic diversity in these butterfly species. As alternatives, we consider linked selection and GC content. We find evidence that high values of both reduce diversity. We also show that the joint effects of gBGC and mutation bias can give rise to a diversity pattern which resembles the signature of linked selection. Consequently, gBGC should be considered when interpreting the effects of linked selection on levels of genetic diversity.
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| 8. |
- Boman, Jesper, et al.
(författare)
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The Genome of Blue-Capped Cordon-Bleu Uncovers Hidden Diversity of LTR Retrotransposons in Zebra Finch
- 2019
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Ingår i: Genes. - : MDPI. - 2073-4425. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- Avian genomes have perplexed researchers by being conservative in both size and rearrangements, while simultaneously holding the blueprints for a massive species radiation during the last 65 million years (My). Transposable elements (TEs) in bird genomes are relatively scarce but have been implicated as important hotspots for chromosomal inversions. In zebra finch (Taeniopygia guttata), long terminal repeat (LTR) retrotransposons have proliferated and are positively associated with chromosomal breakpoint regions. Here, we present the genome, karyotype and transposons of blue-capped cordon-bleu (Uraeginthus cyanocephalus), an African songbird that diverged from zebra finch at the root of estrildid finches 10 million years ago (Mya). This constitutes the third linked-read sequenced genome assembly and fourth in-depth curated TE library of any bird. Exploration of TE diversity on this brief evolutionary timescale constitutes a considerable increase in resolution for avian TE biology and allowed us to uncover 4.5 Mb more LTR retrotransposons in the zebra finch genome. In blue-capped cordon-bleu, we likewise observed a recent LTR accumulation indicating that this is a shared feature of Estrildidae. Curiously, we discovered 25 new endogenous retrovirus-like LTR retrotransposon families of which at least 21 are present in zebra finch but were previously undiscovered. This highlights the importance of studying close relatives of model organisms.
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| 9. |
- Carlsson, Sven G., 1935, et al.
(författare)
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Dental anxiety - a joint interest for dentists and psychologists.
- 2013
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Ingår i: European journal of oral sciences. - : Wiley. - 1600-0722 .- 0909-8836. ; 121:3 Pt 2, s. 221-224
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Tidskriftsartikel (refereegranskat)abstract
- This introductory article to the Symposium on Behavioral and Community Dentistry aims to describe the development of research and clinical work on dental anxiety, and includes a discussion of the historical background and the evolution since the 1970s. In view of its pioneering activities in this regard, special focus is placed on research and development at the Institute of Odontology of the University of Gothenburg, Sweden.
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| 10. |
- Fondell, Mattis, et al.
(författare)
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Optical quantum confinement in low dimensional hematite
- 2014
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488. ; 2:10, s. 3352-3363
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Tidskriftsartikel (refereegranskat)abstract
- Hematite is considered to be a promising material for various applications, including for example photoelectrochemical cells for solar hydrogen production. Due to limitations in the charge transport properties hematite needs to be in the form of low-dimensional particles or thin films in several of these applications. This may however affect the optical properties, introducing additional complications for efficient design of photo-active devices. In this paper the optical absorption is analyzed in detail as a function of film thickness for 35 thin films of hematite ranging between 2 and 70 nm. Hematite was deposited by atomic layer deposition on FTO-substrates using Fe(CO)(5) and O-2 as precursors. It was found that for film thicknesses below 20 nm the optical properties are severely affected as a consequence of quantum confinement. One of the more marked effects is a blue shift of up to 0.3 eV for thinner films of both the indirect and direct transitions, as well as a 0.2 eV shift of the absorption maximum. The data show a difference in quantum confinement for the indirect and the direct transitions, where the probability for the indirect transition decreases markedly and essentially disappears for the thinnest films. Raman measurements showed no peak shift or change in relative intensity for vibrations for the thinnest films indicating that the decrease in indirect transition probability could not be assigned to depression of any specific phonon but instead seems to be a consequence of isotropic phonon confinement. The onset of the indirect transition is found at 1.75 eV for the thickest films and shifted to 2.0 eV for the thinner films. Two direct transitions are found at 2.15 eV and 2.45 eV, which are blue shifted 0.3 and 0.45 eV respectively, when decreasing the film thickness from 20 to 4 nm. Low dimensional hematite, with dimensions small enough for efficient charge transport, thus has a substantially lower absorption in the visible region than expected from bulk values. This knowledge of the intrinsic optical behavior of low dimensional hematite will be of importance in the design of efficient photo-active devices.
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