| 1. |
- Sørensen, Jesper G., et al.
(författare)
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Pronounced Plastic and Evolutionary Responses to Unpredictable Thermal Fluctuations in Drosophila simulans
- 2020
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Ingår i: Frontiers in Genetics. - : Frontiers Media SA. - 1664-8021. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Organisms are exposed to temperatures that vary, for example on diurnal and seasonal time scales. Thus, the ability to behaviorally and/or physiologically respond to variation in temperatures is a fundamental requirement for long-term persistence. Studies on thermal biology in ectotherms are typically performed under constant laboratory conditions, which differ markedly from the variation in temperature across time and space in nature. Here, we investigate evolutionary adaptation and environmentally induced plastic responses of Drosophila simulans to no fluctuations (constant), predictable fluctuations or unpredictable fluctuations in temperature. We whole-genome sequenced populations exposed to 20 generations of experimental evolution under the three thermal regimes and examined the proteome after short-term exposure to the same three regimes. We find that unpredictable fluctuations cause the strongest response at both genome and proteome levels. The loci showing evolutionary responses were generally unique to each thermal regime, but a minor overlap suggests either common laboratory adaptation or that some loci were involved in the adaptation to multiple thermal regimes. The evolutionary response, i.e., loci under selection, did not coincide with induced responses of the proteome. Thus, genes under selection in fluctuating thermal environments are distinct from genes important for the adaptive plastic response observed within a generation. This information is key to obtain a better understanding and prediction of the effects of future increases in both mean and variability of temperatures.
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| 2. |
- Bechsgaard, Jesper, et al.
(författare)
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Evidence for Faster X Chromosome Evolution in Spiders
- 2019
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Ingår i: Molecular biology and evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 36:6, s. 1281-1293
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Tidskriftsartikel (refereegranskat)abstract
- In species with chromosomal sex determination, X chromosomes are predicted to evolve faster than autosomes because of positive selection on recessive alleles or weak purifying selection. We investigated X chromosome evolution in Stegodyphus spiders that differ in mating system, sex ratio, and population dynamics. We assigned scaffolds to X chromosomes and autosomes using a novel method based on flow cytometry of sperm cells and reduced representation sequencing. We estimated coding substitution patterns (dN/dS) in a subsocial outcrossing species (S. africanus) and its social inbreeding and female-biased sister species (S. mimosarum), and found evidence for faster-X evolution in both species. X chromosome-to-autosome diversity (piX/piA) ratios were estimated in multiple populations. The average piX/piA estimates of S. africanus (0.57 [95% CI: 0.55–0.60]) was lower than the neutral expectation of 0.75, consistent with more hitchhiking events on X-linked loci and/or a lower X chromosome mutation rate, and we provide evidence in support of both. The social species S. mimosarum has a significantly higher piX/piA ratio (0.72 [95% CI: 0.65–0.79]) in agreement with its female-biased sex ratio. Stegodyphus mimosarum also have different piX/piA estimates among populations, which we interpret as evidence for recurrent founder events. Simulations show that recurrent founder events are expected to decrease the piX/piA estimates in S. mimosarum, thus underestimating the true effect of female-biased sex ratios. Finally, we found lower synonymous divergence on X chromosomes in both species, and the male-to-female substitution ratio to be higher than 1, indicating a higher mutation rate in males.
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| 3. |
- Bechsgaard, Jesper, et al.
(författare)
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Impaired immune function accompanies social evolution in spiders
- 2022
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Ingår i: Biology letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 18:12, s. 20220331-20220331
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Tidskriftsartikel (refereegranskat)abstract
- An efficient immune system is essential to the survival of many animals. Sociality increases risk of pathogen transmission, which should select for enhanced immune function. However, two hypotheses instead predict a weakened immune function: relaxed selection caused by social immunity/protection, and reduced efficacy of selection due to inbreeding, reproductive skew and female bias in social species that reduce effective population size and accelerate genetic drift. We assessed the effect of social evolution on immune function in a comparative study of two social spider species and their closely related subsocial sister species (genus Stegodyphus). The haemolymph of social species was less efficient in inhibiting bacterial growth of the potentially pathogenic bacteria Bacillus subtilis than that of subsocial species. Reduced efficacy of selection in social species was supported by comparative genomic analysis showing substantially elevated non-synonymous substitutions in immune genes in one of the social species. We propose that impaired immune function results from reduced efficacy of selection because the evolution of sociality in spiders is accompanied by demographic processes that elevate genetic drift. Positive feedback between pathogen-induced local extinctions and the resulting elevation of genetic drift may further weaken responses to selection by pathogens, and threaten species persistence.
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| 4. |
- Guo, Ya-Long, et al.
(författare)
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Recent speciation of Capsella rubella from Capsella grandiflora, associated with loss of self-incompatibility and an extreme bottleneck
- 2009
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 106:13, s. 5246-5251
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Tidskriftsartikel (refereegranskat)abstract
- Flowering plants often prevent selfing through mechanisms of self-incompatibility (S.I.). The loss of S.I. has occurred many times independently, because it provides short-term advantages in situations where pollinators or mates are rare. The genus Capsella, which is closely related to Arabidopsis, contains a pair of closely related diploid species, the self-incompatible Capsella grandiflora and the self-compatible Capsella rubella. To elucidate the transition to selfing and its relationship to speciation of C. rubella, we have made use of comparative sequence information. Our analyses indicate that C. rubella separated from C. grandiflora recently ( approximately 30,000-50,000 years ago) and that breakdown of S.I. occurred at approximately the same time. Contrasting the nucleotide diversity patterns of the 2 species, we found that C. rubella has only 1 or 2 alleles at most loci, suggesting that it originated through an extreme population bottleneck. Our data are consistent with diploid speciation by a single, selfing individual, most likely living in Greece. The new species subsequently colonized the Mediterranean by Northern and Southern routes, at a time that also saw the spread of agriculture. The presence of phenotypic diversity within modern C. rubella suggests that this species will be an interesting model to understand divergence and adaptation, starting from very limited standing genetic variation.
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| 5. |
- Hagenblad, Jenny, 1974-, et al.
(författare)
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Linkage Disequilibrium Between Incompatibility Locus Region Genes
- 2006
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Ingår i: Genetics. - Baltimore, MD, USA : The Genetics Society. - 0016-6731 .- 1943-2631. ; 173, s. 1057-1073
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Tidskriftsartikel (refereegranskat)abstract
- We have studied diversity in Arabidopsis lyrata of sequencesorthologous to the ARK3 gene of A. thaliana. Our main goal wasto test for recombination in the S-locus region. In A. thaliana,the single-copy ARK3 gene is closely linked to the non-functionalcopies of the self-incompatibility loci, and the ortholog inA. lyrata (a self-incompatible species) is in the homologousgenome region and is known as Aly8. It is thus of interest totest whether Aly8 sequence diversity is elevated due to closelinkage to the highly polymorphic incompatibility locus, asis theoretically predicted. However, Aly8 is not a single-copygene, and the presence of paralogs could also lead to the appearanceof elevated diversity. We established a typing approach basedon different lengths of Aly8 PCR products and show that mostA. lyrata haplotypes have a single copy, but some have two genecopies, both closely linked to the incompatibility locus, onebeing a pseudogene. We determined the phase of multiple haplotypesin families of plants from Icelandic and other populations.Different Aly8 sequence types are associated with differentSRK alleles, while haplotypes with the same SRK sequences tendto have the same Aly8 sequence. There is evidence of some exchangeof sequences between different Aly8 sequences, making it difficultto determine which ones are allelic or to estimate the diversity.However, the homogeneity of the Aly8 sequences of each S-haplotypesuggests that recombination between the loci has been very infrequentover the evolutionary history of these populations. Overall,the results suggest that recombination rarely occurs in theinterval between the S-loci and Aly8 and that linkage to theS-loci can probably account for the observed high Aly8 diversity.
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| 6. |
- Rose, Clémence, et al.
(författare)
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The role of inter-individual intolerance in group cohesion and the transition to sociality in spiders
- 2022
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1010-061X .- 1420-9101. ; 35:7, s. 1020-1026
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Tidskriftsartikel (refereegranskat)abstract
- Conspecific tolerance is key for maintaining group cohesion in animals. Understanding shifts from conspecific tolerance to intolerance is therefore important for understanding transitions to sociality. Subsocial species disperse to a solitary lifestyle after a gregarious juvenile phase and display conspecific intolerance as adults as a mechanism to maintain a solitary living. The development of intolerance towards group members is hypothesized to play a role in dispersal decisions in subsocial species. One hypothesis posits that dispersal is triggered by factors such as food competition with the subsequent development of conspecific intolerance, rather than conspecific intolerance developing prior to and potentially driving dispersal. Consistent with this hypothesis, we show that intolerance (inferred by inter-individual distance) developed post-dispersal in the subsocial spider Stegodyphus lineatus. The development of conspecific intolerance was delayed when maintaining spiders in groups showing plasticity in this trait, which is advantageous when trade-offs are not fixed over time. However, major evolutionary transitions, such as the transition to sociality, can permanently modify trade-offs and cause derived adaptations by the evolution of new or modified traits or evolutionary loss of traits that become redundant. Sociality in spiders has evolved repeatedly from subsocial ancestors, and social life in family groups combined with a lack of interaction with competing groups suggests relaxed selection for the development of conspecific intolerance. In the social Stegodyphus sarasinorum we found no evidence for the development of conspecific intolerance, consistent with the loss of this trait. Instead, we found evidence for conspecific attraction, which is likely to govern group cohesion.
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| 7. |
- Schwager, Evelyn E., et al.
(författare)
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The house spider genome reveals an ancient whole-genome duplication during arachnid evolution
- 2017
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Ingår i: BMC Biology. - : BIOMED CENTRAL LTD. - 1741-7007. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Background: The duplication of genes can occur through various mechanisms and is thought to make a major contribution to the evolutionary diversification of organisms. There is increasing evidence for a large-scale duplication of genes in some chelicerate lineages including two rounds of whole genome duplication (WGD) in horseshoe crabs. To investigate this further, we sequenced and analyzed the genome of the common house spider Parasteatoda tepidariorum.Results: We found pervasive duplication of both coding and non-coding genes in this spider, including two clusters of Hox genes. Analysis of synteny conservation across the P. tepidariorum genome suggests that there has been an ancient WGD in spiders. Comparison with the genomes of other chelicerates, including that of the newly sequenced bark scorpion Centruroides sculpturatus, suggests that this event occurred in the common ancestor of spiders and scorpions, and is probably independent of the WGDs in horseshoe crabs. Furthermore, characterization of the sequence and expression of the Hox paralogs in P. tepidariorum suggests that many have been subject to neo-functionalization and/or sub-functionalization since their duplication.Conclusions: Our results reveal that spiders and scorpions are likely the descendants of a polyploid ancestor that lived more than 450 MYA. Given the extensive morphological diversity and ecological adaptations found among these animals, rivaling those of vertebrates, our study of the ancient WGD event in Arachnopulmonata provides a new comparative platform to explore common and divergent evolutionary outcomes of polyploidization events across eukaryotes.
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