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Sökning: WFRF:(Backström Niclas) > Vila Roger

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1.
  • Boman, Jesper, et al. (författare)
  • Environmental stress during larval development induces DNA methylation shifts in the migratory painted lady butterfly (Vanessa cardui)
  • 2023
  • Ingår i: Molecular Ecology. - : John Wiley & Sons. - 0962-1083 .- 1365-294X. ; 32:13, s. 3513-3523
  • 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.
  • Garcia-Berro, Aurora, et al. (författare)
  • Migratory behaviour is positively associated with genetic diversity in butterflies
  • 2023
  • Ingår i: Molecular Ecology. - : John Wiley & Sons. - 0962-1083 .- 1365-294X. ; 32:3, s. 560-574
  • Tidskriftsartikel (refereegranskat)abstract
    • Migration is typically associated with risk and uncertainty at the population level, but little is known about its cost–benefit trade-offs at the species level. Migratory insects in particular often exhibit strong demographic fluctuations due to local bottlenecks and outbreaks. Here, we use genomic data to investigate levels of heterozygosity and long-term population size dynamics in migratory insects, as an alternative to classical local and short-term approaches such as regional field monitoring. We analyse whole-genome sequences from 97 Lepidoptera species and show that individuals of migratory species have significantly higher levels of genome-wide heterozygosity, a proxy for effective population size, than do nonmigratory species. Also, we contribute whole-genome data for one of the most emblematic insect migratory species, the painted lady butterfly (Vanessa cardui), sampled across its worldwide distributional range. This species exhibits one of the highest levels of genomic heterozygosity described in Lepidoptera (2.95 ± 0.15%). Coalescent modelling (PSMC) shows historical demographic stability in V. cardui, and high effective population size estimates of 2–20 million individuals 10,000 years ago. The study reveals that the high risks associated with migration and local environmental fluctuations do not seem to decrease overall genetic diversity and demographic stability in migratory Lepidoptera. We propose a “compensatory” demographic model for migratory r-strategist organisms in which local bottlenecks are counterbalanced by reproductive success elsewhere within their typically large distributional ranges. Our findings highlight that the boundaries of populations are substantially different for sedentary and migratory insects, and that, in the latter, local and even regional field monitoring results may not reflect whole population dynamics. Genomic diversity patterns may elucidate key aspects of an insect's migratory nature and population dynamics at large spatiotemporal scales.
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3.
  • Höök, Lars, et al. (författare)
  • Dualistic dosage compensation and rapid evolution of expression balance in response to W chromosome degeneration in Leptidea butterflies
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • The evolution of dimorphic sex chromosomes from initially homologous autosomes is generally explained by sex-specific selection to maintain linkage between a sex determining locus and genes that are beneficial to the same sex. While initially beneficial, the strong linkage and reduced recombination causes differentiation and degeneration of many initially shared genes. Reduced copy numbers can have severe consequences for the balance of gene expression levels between sex-linked genes and the rest of the genome. Consequently, dosage compensation has evolved independently in different lineages to mitigate the detrimental effects of unbalanced expression of sex-linked genes in the heterogametic sex. However, the variation in sex chromosome regulation in different lineages, puts the need to restore expression to ancestral levels into question. In particular, a general difference has been observed between male- (XY) and female-heterogametic (ZW) systems. In contrast to the X chromosome upregulation in heterogametic males in the XY-systems, the Z chromosomes are rarely upregulated in the heterogametic females in organisms with ZW-systems. Instead, the Z chromosomes are often downregulated in the homogametic males to achieve inter-sexual balance. Although progress has been made to understand what causes this discrepancy, comparative approaches are limited by long divergence times and ancient sex chromosome systems. An attractive approach is therefore to study the evolution of gene regulation on recently derived neo-sex chromosomes, formed through fusions between ancestral sex chromosomes and autosomes. Here, we investigated dosage compensation of neo-sex chromosomes in three closely related butterflies in the cryptic wood white clade (Leptidea). Importantly, the species have acquired multiple sex chromosomes, and dosage compensation could therefore have evolved repeatedly in the clade. Our analyses reveal a mixture of gene expression patterns which suggests that distinct modes of dosage compensation have evolved on the different Z chromosomes. In addition, we detect evidence that dosage balancing mechanisms have been rapidly recruited to the youngest neo-Z chromosome, to counteract an ongoing degeneration of neo-W gametologs. The results add to a growing list of examples where diverse dosage compensation mechanisms can evolve within a single species, and suggests that various regulatory mechanisms are not restricted to specific sex chromosome systems.
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4.
  • Höök, Lars, et al. (författare)
  • High-density linkage maps and chromosome level genome assemblies unveil direction and frequency of extensive structural rearrangements in wood white butterflies (Leptidea spp.)
  • Tidskriftsartikel (refereegranskat)abstract
    • Karyotypes are generally conserved between closely related species and large chromosome rearrangements typically have negative fitness consequences in heterozygotes, potentially driving speciation. In the order Lepidoptera, most investigated species have the ancestral karyotype and gene synteny is often conserved across deep divergence, although examples of extensive genome reshuffling have recently been demonstrated. The genus Leptidea has an unusual level of chromosome variation and rearranged sex chromosomes, but the extent of restructuring across the rest of the genome is so far unknown. To explore the genomes of the wood white (Leptidea) species complex, we generated eight genome assemblies using a combination of 10X linked reads and HiC data, and improved them using linkage maps for two populations of the common wood white (L. sinapis) with distinct karyotypes. Synteny analysis revealed an extensive amount of rearrangements, both compared to the ancestral karyotype and between the Leptidea species, where only one of the three Z chromosomes was conserved across all comparisons. Most restructuring was explained by fissions and fusions, while translocations appear relatively rare. We further detected several examples of segregating rearrangement polymorphisms supporting a highly dynamic genome evolution in this clade. Fusion breakpoints were enriched for LINEs and LTR elements, which suggests that ectopic recombination might be an important driver in the formation of new chromosomes. Our results show that chromosome count alone may conceal the extent of genome restructuring and we propose that the amount of genome evolution in Lepidoptera might still be underestimated due to lack of taxonomic sampling.
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5.
  • Höök, Lars, 1980-, et al. (författare)
  • Temporal dynamics of faster neo-Z evolution in butterflies
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • The faster-Z/X hypothesis predicts that sex-linked genes should diverge faster than autosomal genes and may therefore play important roles in speciation. However, studies across different lineages have shown mixed support for this effect, a variation that has been explained by various evolutionary mechanisms. So far, most analyses have focused on systems with old and well differentiated sex chromosomes, but less is known about divergence of more recently acquired neo-sex chromosomes. In the female heterogametic order Lepidoptera (moths and butterflies), fusions between the ancestral Z chromosome and autosomes are relatively frequent, but the evolutionary dynamics of neo Z-linked genes have not been explored in detail. Here, we analysed the faster-Z effect in Leptidea sinapis, a butterfly with an exceptionally reorganized genome and three Z chromosomes. We show that the neo-Z chromosomes have been acquired in a stepwise fashion, resulting in distinct strata of differentiation and masculinization. While Z-linked divergence generally seems to have been driven by adaptive processes, the relative effects of selection and drift showed a temporal trend where selection has been more prevalent for genes located on older Z linked regions, causing increased divergence of Z-linked genes with female-biased expression. In contrast, the intensity of selection on genes located on the most recently acquired neo-Z chromosome (Z3) appears to have been hampered by the presence of gametologs on the largely intact, homologous neo-W chromosome. However, the intermediately aged neo-Z chromosome (Z2), which is completely differentiated from W gametologs, showed less evolutionary constraint than the ancestral Z, resulting in particularly fast evolution. Our results therefore support that neo-sex chromosomes can constitute temporary hot-spots of adaptation and divergence. The underlying dynamics are likely causally linked to shifts in selective constraints, evolution of gene expression and the degeneration of W-linked gametologs which gradually expose Z-linked genes to selection.
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6.
  • Leal, Luis, et al. (författare)
  • Gene expression profiling across ontogenetic stages in the wood white (Leptidea sinapis) reveals pathways linked to butterfly diapause regulation
  • 2018
  • Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 27:4, s. 935-948
  • Tidskriftsartikel (refereegranskat)abstract
    • In temperate latitudes, many insects enter diapause (dormancy) during the cold season, a period during which developmental processes come to a standstill. The wood white (Leptidea sinapis) is a butterfly species distributed across western Eurasia that shows photoperiod-induced diapause with variation in critical day-length across populations at different latitudes. We assembled transcriptomes and estimated gene expression levels at different developmental stages in experimentally induced directly developing and diapausing cohorts of a single Swedish population of L. sinapis to investigate the regulatory mechanisms underpinning diapause initiation. Different day lengths resulted in expression changes of developmental genes and affected the rate of accumulation of signal molecules, suggesting that diapause induction might be controlled by increased activity of monoamine neurotransmitters in larvae reared under short-day light conditions. Expression differences between light treatment groups of two monoamine regulator genes (DDC and ST) were observed already in instar III larvae. Once developmental pathways were irreversibly set at instar V, a handful of genes related to dopamine production were differentially expressed leading to a significant decrease in expression of global metabolic genes and increase in expression of genes related to fatty acid synthesis and sequestration. This is in line with a time-dependent (hour-glass) model of diapause regulation where a gradual shift in the concentration of monoamine neurotransmitters and their metabolites during development of larvae under short-day conditions leads to increased storage of fat, decreased energy expenditures, and ultimately developmental stasis at the pupal stage.
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7.
  • Näsvall, Karin, et al. (författare)
  • Activity profiles of regulatory elements and associations with the oogenesis-flight syndrome in a long-distance butterfly migrant.
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • The oogenesis-flight syndrome reflects the temporal allocation of energy resources between dispersal / migration and reproduction and is a key concept in research on migratory behaviour in animals. Here, we used an experimental set-up to assess how variation in host plant abundance affected the activity of regulatory elements in the painted lady butterfly (Vanessa cardui), a model species for insect migratory behaviour studies. The results indicate that recently eclosed females that had access to host plants invested in reproduction at an earlier stage and that variation in host plant abundance triggered significant differences in regulatory element activity via acetylation. By analysing functions of genes in the vicinity of significant differences in regulatory activity we pinpointed a set of categories that can be relevant for how females perceive the environment and allocate resources for either migration or reproduction. The functions of genes in the vicinity of differentially activated regions were associated with metabolism, egg shell formation, female receptivity, muscle activity, pheromone binding and mini-chromosome maintenance. Our results provide a first glimpse into the regulatory underpinnings of the oogenesis-flight syndrome and a starting point for more detailed understanding of the links between environmental variation, gene regulation and migratory behaviour in butterflies.
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8.
  • Näsvall, Karin, et al. (författare)
  • Host plant diet affects growth and induces altered gene expression and microbiome composition in the wood white (Leptidea sinapis) butterfly
  • 2021
  • Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 30:2, s. 499-516
  • Tidskriftsartikel (refereegranskat)abstract
    • In a time with decreasing biodiversity, especially among insects, a detailed understanding about specific resource utilization strategies is crucial. The physiological and behavioural responses to host switches in phytophagous insects are poorly understood. Earlier studies indicate that a host plant switch might be associated with distinctive molecular and physiological responses in different lineages. Expanding the assessment of such associations across Lepidoptera will reveal if there are general patterns in adaptive responses, or if each switch event is more of a unique character. We investigated host plant preference, fitness consequences, effects on expression profiles and gut microbiome composition in two common wood white (Leptidea sinapis) populations with different host plant preferences from the extremes of the species distribution area (Sweden and Catalonia). Our results show that female Catalonian wood whites lack preference for either host plant (Lotus corniculatus or L. dorycnium), while Swedish females laid significantly more eggs on L. corniculatus. Individuals from both populations reared on L. dorycnium had longer developmental times and smaller body size as adults. This indicates that both environmental and genetic factors determine the choice to use a specific host plant. Gene expression analysis revealed a more pronounced response to host plant in the Catalonian compared to the Swedish population. In addition, host plant treatment resulted in a significant shift in microbiome community structure in the Catalonian population. Together, this suggests that population specific plasticity associated with local conditions underlies host plant utilisation in wood whites.
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9.
  • Näsvall, Karin, et al. (författare)
  • Nascent evolution of recombination rate as a consequence of chromosomal rearrangements.
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Reshuffling of genetic variation occurs both by independent assortment of chromosomes and by homologous recombination. Such reshuffling can generate novel allele combinations and break linkage between advantageous and deleterious variants which increases both the potential and the efficacy of natural selection. Here we used high-density linkage maps to characterize global and regional recombination rate variation in two populations of the wood white butterfly (Leptidea sinapis) with distinct karyotypes. The recombination data were combined with estimates of genetic diversity and measures of selection to assess associations between chromosomal rearrangements, crossing over, maintenance of genetic diversity and adaptation. Our data show that the recombination rate is influenced by both chromosome size and karyotype, but that the difference in recombination rate between karyotypes is reduced as a consequence of a higher frequency of double crossovers in larger chromosomes. As expected from effects of selection on linked sites, we observed an overall positive association between recombination rate and genetic diversity in both populations. Our results also revealed a significant effect of chromosomal rearrangements on the rate of intergenic diversity change between populations, but limited effects on polymorphisms in coding sequence. We conclude that chromosomal rearrangements can have considerable effects on the recombination landscape and consequently influence both maintenance of genetic diversity and efficiency of selection in natural populations.
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10.
  • Näsvall, Karin, et al. (författare)
  • Nascent evolution of recombination rate differences as a consequence of chromosomal rearrangements
  • 2023
  • Ingår i: PLOS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 19:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Reshuffling of genetic variation occurs both by independent assortment of chromosomes and by homologous recombination. Such reshuffling can generate novel allele combinations and break linkage between advantageous and deleterious variants which increases both the potential and the efficacy of natural selection. Here we used high-density linkage maps to characterize global and regional recombination rate variation in two populations of the wood white butterfly (Leptidea sinapis) that differ considerably in their karyotype as a consequence of at least 27 chromosome fissions and fusions. The recombination data were compared to estimates of genetic diversity and measures of selection to assess the relationship between chromosomal rearrangements, crossing over, maintenance of genetic diversity and adaptation. Our data show that the recombination rate is influenced by both chromosome size and number, but that the difference in the number of crossovers between karyotypes is reduced as a consequence of a higher frequency of double crossovers in larger chromosomes. As expected from effects of selection on linked sites, we observed an overall positive association between recombination rate and genetic diversity in both populations. Our results also revealed a significant effect of chromosomal rearrangements on the rate of intergenic diversity change between populations, but limited effects on polymorphisms in coding sequence. We conclude that chromosomal rearrangements can have considerable effects on the recombination landscape and consequently influence both maintenance of genetic diversity and efficiency of selection in natural populations.
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