| 1. |
- Hill, Jason, et al.
(författare)
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Unprecedented reorganization of holocentric chromosomes provides insights into the enigma of lepidopteran chromosome evolution
- 2019
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 5:6
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Tidskriftsartikel (refereegranskat)abstract
- Chromosome evolution presents an enigma in the mega-diverse Lepidoptera. Most species exhibit constrained chromosome evolution with nearly identical haploid chromosome counts and chromosome-level gene collinearity among species more than 140 million years divergent. However, a few species possess radically inflated chromosomal counts due to extensive fission and fusion events. To address this enigma of constraint in the face of an exceptional ability to change, we investigated an unprecedented reorganization of the standard lepidopteran chromosome structure in the green-veined white butterfly (Pieris napi). We find that gene content in P. napi has been extensively rearranged in large collinear blocks, which until now have been masked by a haploid chromosome number close to the lepidopteran average. We observe that ancient chromosome ends have been maintained and collinear blocks are enriched for functionally related genes suggesting both a mechanism and a possible role for selection in determining the boundaries of these genome-wide rearrangements.
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| 2. |
- Ravikanthachari, Nitin, et al.
(författare)
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Patterns of genetic variation and local adaptation of a native herbivore to a lethal invasive plant
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Ingår i: Molecular Ecology. - 0962-1083.
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the evolutionary processes that influence fitness is critical to predicting species' responses to selection. Interactions among evolutionary processes including gene flow, drift and the strength of selection can lead to either local adaptation or maladaptation, especially in heterogenous landscapes. Populations experiencing novel environments or resources are ideal for understanding the mechanisms underlying adaptation or maladaptation, specifically in locally co-evolved interactions. We used the interaction between a native herbivore that oviposits on a patchily distributed introduced plant that in turn causes significant mortality to the larvae to test for signatures of local adaptation in areas where the two co-occurred. We used whole-genome sequencing to explore population structure, patterns of gene flow and signatures of local adaptation. We found signatures of local adaptation in response to the introduced plant in the absence of strong population structure with no genetic differentiation and low genetic variation. Additionally, we found localized allele frequency differences within a single population between habitats with and without the lethal plant, highlighting the effects of strong selection. Finally, we identified that selection was acting on larval ability to feed on the plant rather than on females' ability to avoid oviposition, thus uncovering the specific ontogenetic target of selection. Our work highlights the potential for adaptation to occur in a fine-grained landscape in the presence of gene flow and low genetic variation.
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| 3. |
- Steward, Rachel A., et al.
(författare)
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Novel host unmasks heritable variation in plant preference within an insect population
- 2022
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 76:11, s. 2634-2648
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Tidskriftsartikel (refereegranskat)abstract
- Introductions of novel plant species can disturb the historical resource environment of herbivorous insects, resulting in strong selection to either adopt or exclude the novel host. However, an adaptive response depends on heritable genetic variation for preference or performance within the targeted herbivore population, and it is unclear how heritability of host-use preference may differ between novel and historical hosts. Pieris macdunnoughii butterflies in the Rocky Mountains lay eggs on the nonnative mustard Thlaspi arvense, which is lethal to their offspring. Heritability analyses revealed considerable sex-linked additive genetic variation in host preference within a population of this butterfly. This was contrary to general predictions about the genetic basis of preference variation, which are hypothesized to be sex linked between populations but autosomal within populations. Evidence of sex linkage disappeared when butterflies were tested on methanol-based chemical extracts, suggesting these chemicals in isolation may not be the primary driver of female choice among available host plants. Although unexpected, evidence for within-population sex-linked genetic variation in preference for T. arvense over native hosts indicates that persistent maladaptive oviposition on this lethal plant must be maintained by alternative evolutionary dynamics such as migration- or drift-selection balance or pleiotropic constraints.
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| 4. |
- Steward, Rachel A., et al.
(författare)
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The Genome of the Margined White Butterfly (Pieris macdunnoughii) : Sex Chromosome Insights and the Power of Polishing with PoolSeq Data
- 2021
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Ingår i: Genome Biology and Evolution. - : Oxford University Press (OUP). - 1759-6653. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- We report a chromosome-level assembly for Pieris macdunnoughii, a North American butterfly whose involvement in an evolutionary trap imposed by an invasive Eurasian mustard has made it an emerging model system for studying maladaptation in plant-insect interactions. Assembled using nearly 100x coverage of Oxford Nanopore long reads, the contig-level assembly comprised 106 contigs totaling 316,549,294 bases, with an N50 of 5.2Mb. We polished the assembly with PoolSeq Illumina short-read data, demonstrating for the first time the comparable performance of individual and pooled short reads as polishing data sets. Extensive synteny between the reported contig-level assembly and a published, chromosome-level assembly of the European butterfly Pieris napi allowed us to generate a pseudochromosomal assembly of 47 contigs, placing 91.1% of our 317 Mb genome into a chromosomal framework. Additionally, we found support for a Z chromosome arrangement in P. napi, showing that the fusion event leading to this rearrangement predates the split between European and North American lineages of Pieris butterflies. This genome assembly and its functional annotation lay the groundwork for future research into the genetic basis of adaptive and maladaptive egg-laying behavior by P. macdunnoughii, contributing to our understanding of the susceptibility and responses of insects to evolutionary traps.
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