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  • Svensson, Erik I, et al. (författare)
  • Effects of natural and sexual selection on adaptive population divergence and premating isolation in a damselfly.
  • 2006
  • Ingår i: Evolution. - : Wiley-Blackwell. - 0014-3820 .- 1558-5646. ; 60:6, s. 1242-53
  • Tidskriftsartikel (refereegranskat)abstract
    • The relative strength of different types of directional selection has seldom been compared directly in natural populations. A recent meta-analysis of phenotypic selection studies in natural populations suggested that directional sexual selection may be stronger in magnitude than directional natural selection, although this pattern may have partly been confounded by the different time scales over which selection was estimated. Knowledge about the strength of different types of selection is of general interest for understanding how selective forces affect adaptive population divergence and how they may influence speciation. We studied divergent selection on morphology in parapatric, natural damselfly (Calopteryx splendens) populations. Sexual selection was stronger than natural selection measured on the same traits, irrespective of the time scale over which sexual selection was measured. Visualization of the fitness surfaces indicated that population divergence in overall morphology is more strongly influenced by divergent sexual selection rather than natural selection. Courtship success of experimental immigrant males was lower than that of resident males, indicating incipient sexual isolation between these populations. We conclude that current and strong sexual selection promotes adaptive population divergence in this species and that premating sexual isolation may have arisen as a correlated response to divergent sexual selection. Our results highlight the importance of sexual selection, rather than natural selection in the adaptive radiation of odonates, and supports previous suggestions that divergent sexual selection promotes speciation in this group.
  • Svensson, Erik I., et al. (författare)
  • Evolutionary dynamics and population biology of a polymorphic insect
  • 2005
  • Ingår i: Journal of Evolutionary Biology. - : John Wiley and Sons. - 1010-061X .- 1420-9101. ; 18:6, s. 1503-1514
  • Tidskriftsartikel (refereegranskat)abstract
    • Conspicuous heritable polymorphisms are useful to address the question if morph frequencies are stable or whether they fluctuate between generations. Ecological geneticists have studied colour polymorphisms in the past, but there are few long-term studies of genetic dynamics across multiple generations. We studied morph-frequency dynamics and female fecundity in the trimorphic blue-tailed damselfly (Ischnura elegans). The morphs include a male-coloured (androchrome) type of female, which is thought to be maintained by frequency-dependent sexual conflict. Morph frequencies changed significantly between years across all populations. There was evidence for directional frequency change since androchrome females increased in 9 of 10 populations across a 4-year period. There was heterogeneity between populations in their evolutionary trajectories, partly caused by population age: androchrome frequencies were initially high in young populations but gradually decreased and approached the level of old populations. We discuss the possible causes of morph-frequency fluctuations, and the role of morph-specific fecundity, dispersal and other forces influencing evolutionary dynamics in this system.
  • Svensson, Erik I., et al. (författare)
  • Female polymorphism, frequency dependence, and rapid evolutionary dynamics in natural populations
  • 2005
  • Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 165:5, s. 567-76
  • Tidskriftsartikel (refereegranskat)abstract
    • Rapid evolutionary change over a few generations has been documented in natural populations. Such changes are observed as organisms invade new environments, and they are often triggered by changed interspecific interactions, such as differences in predation regimes. However, in spite of increased recognition of antagonistic male-female mating interactions, there is very limited evidence that such intraspecific interactions could cause rapid evolutionary dynamics in nature. This is because ecological and longitudinal data from natural populations have been lacking. Here we show that in a color-polymorphic damselfly species, male-female mating interactions lead to rapid evolutionary change in morph frequencies between generations. Field data and computer simulations indicate that these changes are driven by sexual conflict, in which morph fecundities are negatively affected by frequency- and density-dependent male mating harassment. These frequency-dependent processes prevent population divergence by maintaining a female polymorphism in most populations. Although these results contrast with the traditional view of how sexual conflict enhances the rate of population divergence, they are consistent with a recent theoretical model of how females may form discrete genetic clusters in response to male mating harassment.
  • Svensson, Erik I, et al. (författare)
  • Selective predation on wing morphology in sympatric damselflies.
  • 2007
  • Ingår i: American Naturalist. - : University of Chicago Press. - 1537-5323 .- 0003-0147. ; 170:1, s. 101-12
  • Tidskriftsartikel (refereegranskat)abstract
    • Although predation is thought to affect species divergence, the effects of predator-mediated natural selection on species divergence and in nonadaptive radiations have seldom been studied. Wing melanization in Calopteryx damselflies has important functions in sexual selection and interspecific interactions and in species recognition. The genus Calopteryx and other damselfly genera have also been put forward as examples of radiations driven by sexual selection. We show that avian predation strongly affects natural selection on wing morphology and male wing melanization in two congeneric and sympatric species of this genus (Calopteryx splendens and Calopteryx virgo). Predation risk was almost three times higher for C. virgo, which has an exaggerated degree of wing melanization, than it was for the less exaggerated, sympatric congener C. splendens. Selective predation on the exaggerated species C. virgo favored a reduction and redistribution of the wing melanin patch. There was evidence for nonlinear selection involving wing patch size, wing patch darkness, and wing length and width in C. splendens but weaker nonlinear selection on the same trait combinations in C. virgo. Selective predation could interfere with species divergence by sexual selection and may thus indirectly affect male interspecific interactions, reproductive isolation, and species coexistence in this genus.
  • Svensson, Erik I., et al. (författare)
  • Sex differences in local adaptation : what can we learn from reciprocal transplant experiments?
  • 2018
  • Ingår i: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : ROYAL SOC. - 0962-8436 .- 1471-2970. ; 373:1757
  • Forskningsöversikt (refereegranskat)abstract
    • Local adaptation is of fundamental interest to evolutionary biologists. Traditionally, local adaptation has been studied using reciprocal transplant experiments to quantify fitness differences between residents and immigrants in pairwise transplants between study populations. Previous studies have detected local adaptation in some cases, but others have shown lack of adaptation or even maladaptation. Recently, the importance of different fitness components, such as survival and fecundity, to local adaptation have been emphasized. Here, we address another neglected aspect in studies of local adaptation: sex differences. Given the ubiquity of sexual dimorphism in life histories and phenotypic traits, this neglect is surprising, but may be partly explained by differences in research traditions and terminology in the fields of local adaptation and sexual selection. Studies that investigate differences in mating success between resident and immigrants across populations tend to be framed in terms of reproductive and behavioural isolation, rather than local adaptation. We briefly review the published literature that bridges these areas and suggest that reciprocal transplant experiments could benefit from quantifying both male and female fitness components. Such a more integrative research approach could clarify the role of sex differences in the evolution of local adaptations. 
  • Svensson, Erik I., et al. (författare)
  • The Role of Mutation Bias in Adaptive Evolution
  • 2019
  • Ingår i: Trends in Ecology and Evolution. - : Elsevier. - 0169-5347 .- 1872-8383. ; 34:5, s. 422-434
  • Forskningsöversikt (refereegranskat)abstract
    • Mutational input is the ultimate source of genetic variation, but mutations are not thought to affect the direction of adaptive evolution. Recently, critics of standard evolutionary theory have questioned the random and non-directional nature of mutations, claiming that the mutational process can be adaptive in its own right. We discuss here mutation bias in adaptive evolution. We find little support for mutation bias as an independent force in adaptive evolution, although it can interact with selection under conditions of small population size and when standing genetic variation is limited, entirely consistent with standard evolutionary theory. We further emphasize that natural selection can shape the phenotypic effects of mutations, giving the false impression that directed mutations are driving adaptive evolution.
  • Willink, Beatriz, et al. (författare)
  • Changes in gene expression during female reproductive development in a color polymorphic insect
  • Ingår i: Evolution. - : Wiley-Blackwell. - 0014-3820 .- 1558-5646. ; 74:6, s. 1063-1081
  • Tidskriftsartikel (refereegranskat)abstract
    • Pleiotropy (multiple phenotypic effects of single genes) and epistasis (gene interaction) have key roles in the development of complex phenotypes, especially in polymorphic taxa. The development of discrete and heritable phenotypic polymorphisms often emerges from major-effect genes that interact with other loci and have pleiotropic effects on multiple traits. We quantified gene expression changes during ontogenetic color development in a polymorphic insect (damselfly: Ischnura elegans), with three heritable female morphs, one being a male mimic. This female color polymorphism is maintained by male mating harassment and sexual conflict. Using transcriptome sequencing and de novo assembly, we demonstrate that all three morphs downregulate gene expression during early color development. The morphs become increasingly differentiated during sexual maturation and when developing adult coloration. These different ontogenetic trajectories arise because the male-mimic shows accelerated (heterochronic) development, compared to the other female morphs. Many loci with regulatory functions in reproductive development are differentially regulated in the male-mimic, including upstream and downstream regulators of ecdysone signaling and transcription factors potentially influencing sexual differentiation. Our results suggest that long-term sexual conflict does not only maintain this polymorphism, but has also modulated the evolution of gene expression profiles during color development of these sympatric female morphs.
  • Almqvist, Erik G., et al. (författare)
  • Factors influencing insulin sensitivity in patients with mild primary hyperparathyroidism before and after parathyroidectomy
  • 2012
  • Ingår i: Scandinavian Journal of Clinical & Laboratory Investigation. - : Informa Healthcare. - 1502-7686. ; 72:2, s. 92-99
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives. Primary hyperparathyroidism (PHPT) is associated with cardiovascular disease. The aims of this study were to investigate lipid and glucose metabolism in mild PHPT, and to identify whether insulin sensitivity correlates with circulating levels of adiponectin, SHBG, and osteocalcin before and after parathyroidectomy (PTX). Materials and methods. Forty-five patients with PHPT were examined before and 1 year after PTX. Circulating levels of triglycerides, total cholesterol, HDL-cholesterol, insulin, glucose, adiponectin, SHBG, osteocalcin, and erythropoietin were measured. Results. At baseline, the mean serum levels of total cholesterol, LDL-cholesterol and triglycerides were above the upper reference limit or in the upper normal range, and insulin sensitivity was reduced as assessed using the HOMA index. One year after parathyroidectomy, serum lipids as well as HOMA index and erythropoietin were unchanged while adiponectin had increased (p < 0.05), and SHBG and osteocalcin had decreased (p < 0.05 and p < 0.0001, respectively). HOMA index correlated negatively with circulating levels of adiponectin, SHBG and osteocalcin. In multiple regression analysis SHBG was the most important predictor of insulin sensitivity, both pre- and postoperatively. Conclusion. Untreated mild PHPT is associated with a moderate derangement of lipid and glucose metabolism. As previously shown in population-based cohorts, insulin sensitivity is positively associated with circulating concentrations of adiponectin, SHBG and osteocalcin. One year after PTX, the mean level of adiponectin was increased, but the levels of SHBG and osteocalcin had decreased and the levels of serum lipids and the insulin sensitivity remained unchanged as compared with baseline.
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