| 1. |
- Ahnesjö, Ingrid, et al.
(författare)
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Considering gender‑biased assumptions in evolutionary biology
- 2020
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Ingår i: Evolutionary biology. - : Springer Nature. - 0071-3260 .- 1934-2845. ; 47, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- Many organisms studied by evolutionary biologists have different sexes, and the evolution of separate sexes and sexual dimorphisms in morphology and behaviour are central questions in evolutionary biology. Considering scientists to be embedded in a social and cultural context, we are also subjected to the risk of gender-biased assumptions and stereotypical thinking to appear when working on topics related to sexual reproduction and sexual dimorphism. Here we present, for continued discussion, a set of good-practice guidelines aimed at (1) helping to improve researchers’ awareness of gender-biased assumptions underlying language use, generalizations, and interpretation of observations; and (2) providing recommendations to increase transparency, avoid problematic terminology, and improve study designs.
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| 2. |
- Berger, David, et al.
(författare)
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Elevated temperature increases genome-wide selection on de novo mutations
- 2021
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : Royal Society. - 0962-8452 .- 1471-2954. ; 288:1944
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Tidskriftsartikel (refereegranskat)abstract
- Adaptation in new environments depends on the amount of genetic variation available for evolution, and the efficacy by which natural selection discriminates among this variation. However, whether some ecological factors reveal more genetic variation, or impose stronger selection pressures than others, is typically not known. Here, we apply the enzyme kinetic theory to show that rising global temperatures are predicted to intensify natural selection throughout the genome by increasing the effects of DNA sequence variation on protein stability. We test this prediction by (i) estimating temperature-dependent fitness effects of induced mutations in seed beetles adapted to ancestral or elevated temperature, and (ii) calculate 100 paired selection estimates on mutations in benign versus stressful environments from unicellular and multicellular organisms. Environmental stress per se did not increase mean selection on de novo mutation, suggesting that the cost of adaptation does not generally increase in new ecological settings to which the organism is maladapted. However, elevated temperature increased the mean strength of selection on genome-wide polymorphism, signified by increases in both mutation load and mutational variance in fitness. These results have important implications for genetic diversity gradients and the rate and repeatability of evolution under climate change.
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| 3. |
- Berger, David, et al.
(författare)
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Temperature effects on life-history trade-offs, germline maintenance and mutation rate under simulated climate warming
- 2017
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 284:1866
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Tidskriftsartikel (refereegranskat)abstract
- Mutation has a fundamental influence over evolutionary processes, but how evolutionary processes shape mutation rate remains less clear. In asexual unicellular organism, increased mutation rates have been observed in stressful environments and the reigning paradigm ascribes this increase to selection for evolvability. However, this explanation does not apply in sexually reproducing species, where little is known about how the environment affects mutation rate. Here we challenged experimental lines of seed beetle, evolved at ancestral temperature or under simulated climate warming, to repair induced mutations at ancestral and stressful temperature. Results show that temperature stress causes individuals to pass on a greater mutation load to their grand-offspring. This suggests that stress-induced mutation rates, in unicellular and multicellular organisms alike, can result from compromised germline DNA repair in low condition individuals. Moreover, lines adapted to simulated climate warming had evolved increased longevity at the cost of reproduction, and this allocation decision improved germline repair. These results suggest that mutation rates can be modulated by resource allocation trade-offs encompassing life-history traits and the germline and have important implications for rates of adaptation and extinction as well as our understanding of genetic diversity in multicellular organisms.
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| 4. |
- Dylus, D.V., et al.
(författare)
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Large-scale gene expression study in the ophiuroid Amphiura filiformis provides insights into evolution of gene regulatory networks
- 2016
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Ingår i: EvoDevo. - : Springer Science and Business Media LLC. - 2041-9139. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 Dylus et al. Background: The evolutionary mechanisms involved in shaping complex gene regulatory networks (GRN) that encode for morphologically similar structures in distantly related animals remain elusive. In this context, echinoderm larval skeletons found in brittle stars and sea urchins provide an ideal system. Here, we characterize for the first time the development of the larval skeleton in the ophiuroid Amphiura filiformis and compare it systematically with its counterpart in sea urchin. Results: We show that ophiuroids and euechinoids, that split at least 480 Million years ago (Mya), have remarkable similarities in tempo and mode of skeletal development. Despite morphological and ontological similarities, our high-resolution study of the dynamics of genetic regulatory states in A. filiformis highlights numerous differences in the architecture of their underlying GRNs. Importantly, the A.filiformis pplx, the closest gene to the sea urchin double negative gate (DNG) repressor pmar1, fails to drive the skeletogenic program in sea urchin, showing important evolutionary differences in protein function. hesC, the second repressor of the DNG, is co-expressed with most of the genes that are repressed in sea urchin, indicating the absence of direct repression of tbr, ets1/2, and delta in A. filiformis. Furthermore, the absence of expression in later stages of brittle star skeleton development of key regulatory genes, such as foxb and dri, shows significantly different regulatory states. Conclusion: Our data fill up an important gap in the picture of larval mesoderm in echinoderms and allows us to explore the evolutionary implications relative to the recently established phylogeny of echinoderm classes. In light of recent studies on other echinoderms, our data highlight a high evolutionary plasticity of the same nodes throughout evolution of echinoderm skeletogenesis. Finally, gene duplication, protein function diversification, and cis-regulatory element evolution all contributed to shape the regulatory program for larval skeletogenesis in different branches of echinoderms.
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| 5. |
- Grieshop, Karl, et al.
(författare)
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Strong sexual selection in males against a mutation load that reduces offspring production in seed beetles
- 2016
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 29:6, s. 1201-1210
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Tidskriftsartikel (refereegranskat)abstract
- Theory predicts that sexual reproduction can increase population viability relative to asexual reproduction by allowing sexual selection in males to remove deleterious mutations from the population without large demographic costs. This requires that selection acts more strongly in males than females and that mutations affecting male reproductive success have pleiotropic effects on population productivity, but empirical support for these assumptions is mixed. We used the seed beetle Callosobruchus maculatus to implement a three-generation breeding design where we induced mutations via ionizing radiation (IR) in the F-0 generation and measured mutational effects (relative to nonirradiated controls) on an estimate of population productivity in the F-1 and effects on sex-specific competitive lifetime reproductive success (LRS) in the F-2. Regardless of whether mutations were induced via F-0 males or females, they had strong negative effects on male LRS, but a nonsignificant influence on female LRS, suggesting that selection is more efficient in removing deleterious alleles in males. Moreover, mutations had seemingly shared effects on population productivity and competitive LRS in both sexes. Thus, our results lend support to the hypothesis that strong sexual selection on males can act to remove the mutation load on population viability, thereby offering a benefit to sexual reproduction.
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| 6. |
- Nieuwenhuis, Bart P. S., et al.
(författare)
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Repeated evolution of self-compatibility for reproductive assurance
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Sexual reproduction in eukaryotes requires the fusion of two compatible gametes of opposite sexes or mating types. To meet the challenge of finding a mating partner with compatible gametes, evolutionary mechanisms such as hermaphroditism and self-fertilization have repeatedly evolved. Here, by combining the insights from comparative genomics, computer simulations and experimental evolution in fission yeast, we shed light on the conditions promoting separate mating types or self-compatibility by mating-type switching. Analogous to multiple independent transitions between switchers and non-switchers in natural populations mediated by structural genomic changes, novel switching genotypes readily evolved under selection in the experimental populations. Detailed fitness measurements accompanied by computer simulations show the benefits and costs of switching during sexual and asexual reproduction, governing the occurrence of both strategies in nature. Our findings illuminate the trade-off between the benefits of reproductive assurance and its fitness costs under benign conditions facilitating the evolution of self-compatibility.
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| 7. |
- Stångberg, Josefine, 1988-
(författare)
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Evolutionary consequences of sex-specific selection
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sex-specific selection is widespread, evident by the evolution of sexual dimorphism in many traits in sexually reproducing taxa. The reason why the sexes may experience selection that differs in direction or magnitude is often linked to the reproductive strategies associated with the sex-specific reproductive physiology. Competition for mates or fertilisations creates conditions where selection is sex-specific and may overall be stronger on the sex experiencing more competition. However, the sexes share a majority of their genome and consequently many traits may be genetically correlated between the sexes, constraining sex-specific adaptation. In paper I, II and III, I investigate the consequences of exposure to altered strength of sex-specific selection in the laboratory through 30 generations of experimental evolution with skewed sex ratios, using the sexually reproducing nematode Caenorhabditis remanei as a model organism. I created female-biased (FB) and male-biased (MB) treatments. In paper I, I investigated the phenotypic response to selection in three life history traits (body size, fitness and heat shock resistance as a proxy for somatic maintenance). I found a sex-specific response to the evolutionary treatments for body size and fitness, while somatic maintenance was similarly affected by the treatments in the sexes. Subsequently, in paper II, I examined sex-specific patterns of additive genetic variance (VA) for reproductive fitness, and estimated the intersexual genetic correlation (rmf) of fitness. Results show low levels of VA for fitness, and no changes in response to treatments. Values of rmf are associated with large uncertainties, highlighting the difficulties in estimating and interpreting rmf for fitness. In paper III, I used a multivariate approach to investigate the sex-specific genetic variance-covariance matrices (GF and GM), and the between-sex genetic covariance matrix (B) in the three life history traits. Results show no genetic covariances between the traits, and no covariances between the sexes in these traits. The sex-specific G-matrices also remained stable in response to the treatments. These results therefore suggest that the genetic architecture of the traits studied here does not constrain the independent evolution in the sexes. In paper IV, using the seed beetle Callosobruchus maculatus as the model, I find that experimentally induced mutations have stronger negative effects on male than female fitness, suggesting overall stronger selection on males. The results support the theory that strong sexual selection on males have the potential to purge deleterious mutations from a population.
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| 8. |
- Stångberg, Josefine, 1988-, et al.
(författare)
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Experimentally induced intrasexual mating competition and sex‐specific evolution in female and male nematodes
- 2020
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 33:12, s. 1677-1688
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Tidskriftsartikel (refereegranskat)abstract
- Sexual dimorphism in life history traits and their trade‐offs is widespread among sexually reproducing animals and is strongly influenced by the differences in reproductive strategies between the sexes. We investigated how intrasexual competition influenced specific life history traits, important to fitness and their trade‐offs in the outcrossing nematode Caenorhabditis remanei. Here, we altered the strength of sex‐specific selection through experimental evolution with increased potential for intrasexual competition by skewing the adult sex ratio towards either females or males (1:10 or 10:1) over 30 generations and subsequently measured the phenotypic response to selection in three traits related to fitness: body size, fecundity and tolerance to heat stress. We observed a greater evolutionary change in females than males for body size and peak fitness, suggesting that females may experience stronger net selection and potentially harbour higher amounts of standing genetic variance compared to males. Our study highlights the importance of investigating direct and indirect effects of intrasexual competition in both sexes in order to capture sex‐specific responses and understand the evolution of sexual dimorphism in traits expressed by both sexes.
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| 9. |
- Stångberg, Josefine, 1988-, et al.
(författare)
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Sex-specific additive genetic variance for fitness during experimental evolution in a sexually reproducing nematode.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Variation in fitness defines the upper limit of adaptive evolution. Due to an intersexual genetic correlation (rmf) for fitness, the sexes could act as a constraint for the sex-specific evolution of fitness. Additive genetic variance VA is generally lower for fitness than for other traits (such as morphological traits), and its estimation can be challenging. Little is known about how VA and rmf for fitness are affected by sex-specific selection over time. Here, we estimated sex-specific VA and rmf between the sexes for a measure of relative fitness in the outcrossing nematode Caenorhabditis remanei and tested how VA and rmf are affected by evolution under experimentally increased sexual competition. For this we used experimental evolution treatments of skewed sex ratios, creating 1:10 female-biased (FB) and male-biased (MB) conditions, for 30 generations. In line with many other studies we found only a small amount of VA for fitness in both sexes. There was, however, a trend of males having approximately double the amount of VA for fitness than females across the treatments, but no differences between treatments in either sex were detected. Rmf mean values differed across treatments, but these values were estimated with some uncertainty and the differences were not statistically significant. The results indicate that VA for a measure of fitness did not change in response to skewed sex ratios, and males harboured a greater amount of VA for fitness than females, in line with findings in many other systems. This study, being one of the few studies combining quantitative genetics and experimental evolution, highlights the challenge of estimating sex-specific VA for fitness, as well as the complexity of using and interpreting intersexual genetic correlations (rmf).
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| 10. |
- Stångberg, Josefine, 1988-, et al.
(författare)
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Stability of the G- and B-matrices in life history traits under experimental manipulation of sexual competition.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- How sexual dimorphism in life history traits evolves, despite a majority of the genome being shared between the sexes, is a fundamental question in evolutionary biology. To answer this question, we need to understand how traits vary within the sexes, and how they covary between the sexes. Constructing genetic variance-covariance matrices (G) for each sex (GF and GM), and between-sex covariance matrices (B), gives us the genetic architecture of traits within and between the sexes. These matrices can be used to predict sex-specific evolutionary trajectories in a population. Understanding the stabilities of G and B over evolutionary time is key in elucidating how sexual dimorphism evolves despite a shared genome, and one way to test the stability of matrices is to use experimental evolution. In this study, we manipulated ratios separately towards each sex in the nematode Caenorhabditis remanei (female-biased, FB, and male-biased, MB), and let populations evolve under these environments for 30 generations, and subsequently compared them to the ancestral population. We measured three important life history traits (body size, peak reproductive fitness and heat shock tolerance as a proxy for somatic maintenance), estimated standardised phenotypic selection gradients, and constructed GF, GM, and B for each sex and treatment. The three life history traits showed no significant genetic covariances in either sex, and these within-sex G-matrices were similar between the experimental treatments. No significant trait covariances were detected between the sexes either, and the B-matrices also remained similar across the treatments. These results suggest that the genetic architecture of life history traits studied here is largely independent across traits and sexes, and remains stable despite previously reported phenotypic evolution in response to the sex ratio manipulations. There seems to be little constraint to the independent evolution in the sexes, in line with the widespread observation of sexual dimorphism in life history traits. Our results suggest that the directional and stabilising selection gradients for body size has changed in a sex-specific manner in response to treatments.
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