| 1. |
- Björkman, Christer, et al.
(författare)
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High Temperature Triggers Latent Variation among Individuals: Oviposition Rate and Probability for Outbreaks
- 2011
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Background It is anticipated that extreme population events, such as extinctions and outbreaks, will become more frequent as a consequence of climate change. To evaluate the increased probability of such events, it is crucial to understand the mechanisms involved. Variation between individuals in their response to climatic factors is an important consideration, especially if microevolution is expected to change the composition of populations. Methodology/Principal Findings Here we present data of a willow leaf beetle species, showing high variation among individuals in oviposition rate at a high temperature (20°C). It is particularly noteworthy that not all individuals responded to changes in temperature; individuals laying few eggs at 20°C continued to do so when transferred to 12°C, whereas individuals that laid many eggs at 20°C reduced their oviposition and laid the same number of eggs as the others when transferred to 12°C. When transferred back to 20°C most individuals reverted to their original oviposition rate. Thus, high variation among individuals was only observed at the higher temperature. Using a simple population model and based on regional climate change scenarios we show that the probability of outbreaks increases if there is a realistic increase in the number of warm summers. The probability of outbreaks also increased with increasing heritability of the ability to respond to increased temperature. Conclusions/Significance If climate becomes warmer and there is latent variation among individuals in their temperature response, the probability for outbreaks may increase. However, the likelihood for microevolution to play a role may be low. This conclusion is based on the fact that it has been difficult to show that microevolution affect the probability for extinctions. Our results highlight the urge for cautiousness when predicting the future concerning probabilities for extreme population events
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| 2. |
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| 3. |
- Gunnarsson, Niklas, et al.
(författare)
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Increased prevalence of prior malignancies and autoimmune diseases in patients diagnosed with chronic myeloid leukemia
- 2016
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Ingår i: Leukemia. - : Springer Science and Business Media LLC. - 0887-6924 .- 1476-5551. ; 30:7, s. 1562-1567
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Tidskriftsartikel (refereegranskat)abstract
- We recently reported an increased incidence of second malignancies in chronic myeloid leukemia (CML) patients treated with tyrosine kinase inhibitors (TKI). To elucidate whether this increase may be linked, not to TKI but rather to a hereditary or acquired susceptibility to develop cancer, we estimated the prevalence of malignancies, autoimmune disease (AD) and chronic inflammatory disease (CID) in CML patients prior to their CML diagnosis. Nationwide population-based registers were used to identify patients diagnosed with CML in Sweden 2002-2012 and to estimate the prevalence of other malignancies, AD and CID prior to their CML diagnosis. For each patient with CML, five matched controls were selected from the general population. Conditional logistic regression was used to calculate odds ratios (OR). Nine hundred and eighty-four CML patients were assessed, representing more than 45 000 person-years of follow-up. Compared with matched controls, the prevalence of prior malignancies and AD was elevated in CML patients: OR 1.47 (95% confidence interval (CI) 1.20-1.82) and 1.55 (95% CI 1.21-1.98), respectively. No associations were detected between CML and previous CID. An increased prevalence of other malignancies and AD prior to the diagnosis of CML suggest that a hereditary or acquired predisposition to cancer and/or autoimmunity is involved in the pathogenesis of CML.
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| 4. |
- Höglund, Solveig, et al.
(författare)
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A rare major plant QTL determines non-responsiveness to a gall-forming insect in willow
- 2012
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Ingår i: Tree Genetics & Genomes. - : Springer Science and Business Media LLC. - 1614-2942 .- 1614-2950. ; 8:5, s. 1051-1060
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Tidskriftsartikel (refereegranskat)abstract
- Growth and defence are plant traits that determine attack success by sessile herbivorous insects. Models of plant resistance suggest induced resistance to be an especially important mechanism in growth-dominated plant species. Little is known, however, about the effects of absence of induced responses as an alternative resistance mechanism. Large genetically based intraspecific variation in resistance (neonate larval mortality) occurs in Salix viminalis against the gall midge Dasineura marginemtorquens. In certain resistant genotypes, larval mortality is associated with formation of necrotic lesions and biochemical changes commonly found in hypersensitive response (HR). More detailed studies, however, have shown that resistance can occur without HR symptoms. By means of a quantitative trait locus (QTL) analysis, this study tested whether (1) resistance is caused by the HR or (2) by the failure of the midge to initiate a gall (non-responsiveness). One QTL explained 68 and 18 % of the variation in resistance in the experimental population during 2 years of investigation. Co-location of QTLs for resistance and HR was found in only one of the years, i.e. when HR was suppressed. The data suggest that the mechanism of resistance involves non-responsiveness, implying that the insect starves to death due to lack of resources. Such symptomless defence may be more important than previously thought because it is difficult to observe in nature.
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| 5. |
- Höglund, Solveig
(författare)
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Induced responses in willow determine feeding success of a gall-forming insect
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the willow Salix viminalis L. (Salicaceae), growth and defence are key responses determining feeding success of the gall midge Dasineura marginemtorquens Bremi (Diptera: Cecidomyiidae). The interaction includes induced growth (gall formation), and induced defence (hypersensitive response, HR). Salix viminalis exhibits large genotypic variation in resistance (larval mortality) against D. marginemtorquens. This thesis focuses on testing hypotheses developed from field observations of interactions between the willow and the gall midge. A specific aim was to gain insight into the mechanism(s) of resistance. Combined greenhouse and field experiments were used to test whether abiotic factors induce susceptibility in otherwise resistant genotypes at the time of gall initiation. The results suggest that plasticity in plant resistance is linked to ambient conditions, probably light. Resistance was associated with HR, but to different degrees among willow genotypes. Hydrogen peroxide, a marker of HR, was induced in genotypes expressing HR but not in resistant genotypes not showing symptoms. The genetic architecture of plant traits that determine larval mortality and HR was investigated by means of a QTL analysis. The presence of one particular allele at one single locus was enough to determine life or death of the gall midge. The defence hypothesis was not supported when examining the homologous region in the poplar genome. However, an auxin gene was located within the QTL area, lending some support for the starvation and anti-manipulation hypothesis. The place of birth (leaf position) was found to be important for insect fitness, and the quality of a gall seemed to be associated with the duration of the site as a resource sink. In conclusion, data suggest that the mechanism of resistance involves anti-manipulation of growth rather than defence. Such, nonreactivity genes may have pleiotropic effects, and the frequency of genes insensitive to manipulation might be restricted in nature due to selection compared with the gall stimulus phenotype.
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| 6. |
- Höglund, Solveig, et al.
(författare)
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Repellent activity of catmint, Nepeta cataria, and iridoid nepetalactone isomers against Afro-tropical mosquitoes, ixodid ticks and red poultry mites
- 2011
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Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 72, s. 109-114
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Tidskriftsartikel (refereegranskat)abstract
- The repellent activity of the essential oil of the catmint plant, Nepeta cataria (Lamiaceae), and the main iridoid compounds (4aS,7S,7aR) and (4aS,75,7aS)-nepetalactone, was assessed against (i) major Afro-tropical pathogen vector mosquitoes, i.e. the malaria mosquito, Anopheles gambiae s.s. and the Southern house mosquito, Culex quinquefasciatus, using a World Health Organisation (WHO)-approved topical application bioassay (ii) the brown ear tick, Rhipicephalus appendiculatus, using a climbing repellency assay, and (iii) the red poultry mite, Dermanyssus gallinae, using field trapping experiments. Gas chromatography (GC) and coupled GC-mass spectrometry (GC-MS) analysis of two N. cataria chemotypes (A and B) used in the repellency assays showed that (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone were present in different proportions, with one of the oils (from chemotype A) being dominated by the (4aS,75,7aR) isomer (91.95% by GC), and the other oil (from chemotype B) containing the two (4a5,7S,7aR) and (4aS,75,7a5) isomers in 16.98% and 69.83% (by GC), respectively. The sesquiterpene hydrocarbon (E)-(1R,9S)-caryophyllene was identified as the only other major component in the oils (8.05% and 13.19% by GC, respectively). Using the topical application bioassay, the oils showed high repellent activity (chemotype A RD(50) = 0.081 mg cm(-2) and chemotype B RD(50) = 0.091 mg cm(-2)) for An. gambiae comparable with the synthetic repellent DEET (RD(50) = 0.12 mg cm(-2)), whilst for Cx. quinquefasciatus, lower repellent activity was recorded (chemotype A RD(50) = 0.34 mg cm(-2) and chemotype B RD(50) = 0.074 mg cm(-2)). Further repellency testing against An. gambiae using the purified (4a.S.7.5,7aR) and (4aS,7S,7aS)-nepetalactone isomers revealed overall lower repellent activity, compared to the chemotype A and B oils. Testing of binary mixtures of the (4aS,7S,7aR) and (4a5,75,7aS) isomers across a range of ratios, but all at the same overall dose (0.1 mg), revealed not only a synergistic effect between the two, but also a surprising ratio-dependent effect, with lower activity for the pure isomers and equivalent or near-equivalent mixtures, but higher activity for non-equivalent ratios. Furthermore, a binary mixture of (4aS,7S,7aR) and (4aS,75,7aS) isomers, in a ratio equivalent to that found in chemotype B oil, was less repellent than the oil itself, when tested at two doses equivalent to 0.1 and 0.01 mg chemotype B oil. The three-component blend including (E)-(1R,9S)-caryophyllene at the level found in chemotype B oil had the same activity as chemotype B oil. In a tick climbing repellency assay using R. appendiculatus, the oils showed high repellent activity comparable with data for other repellent essential oils (chemotype A RD(50) = 0.005 mg and chemotype B RD(50) = 0.0012 mg). In field trapping assays with D. gallinae, addition of the chemotype A and B oils, and a combination of the two, to traps pre-conditioned with D. gallinae, all resulted in a significant reduction of D. gallinae trap capture. In summary, these data suggest that although the nepetalactone isomers have the potential to be used in human and livestock protection against major pathogen vectors, intact, i.e. unfractionated. Nepeta spp. oils offer potentially greater protection, due to the presence of both nepetalactone isomers and other components such as (E)-(1R,9S)-caryophyllene. (C) 2010 Elsevier Ltd. All rights reserved.
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| 7. |
- Höglund, Solveig
(författare)
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Timing of growth determines fitness and performance of a galling insect on willow
- 2014
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Ingår i: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 39, s. 159-167
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Tidskriftsartikel (refereegranskat)abstract
- Characteristics that determine a plant's quality as herbivore food exhibit within-plant heterogeneity. Most models suggest negative effects from secondary chemicals. Less work has focused on plant growth dynamics that might also be important in creating heterogeneity in the distribution of food resources among leaves within the plant. Gall-forming insects are sessile during their feeding stage and are therefore of particular interest when assessing the relative importance of growth and non-growth processes in plants. Galls act as sinks for photoassimilates, and successful redirection of these resources requires that gall formation takes place in plant modules that are in an active growth phase. The gall midge Dasineura marginemtorquens infests leaves of the fast-growing Salix viminalis. Several young leaves per shoot are used as oviposition sites during any single egg-laying occasion. This study investigates the extent to which growth in leaves that are apparently suitable for gall initiation varies along shoots of S. viminalis, and tests whether or not such variation affects the fitness and performance of D. marginemtorquens. The relative position of the galled leaves along a shoot was found to determine the success of the gall midge in terms of larval survival, larval developmental time, and adult size. Leaf growth dynamics, but not leaf size, was associated with the variation in insect fitness and performance. Thus, when considering habitat quality for a sessile insect like D. marginemtorquens, the length of time that the galling site acts as a photoassimilate sink is more important than the final size of the plant module.
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| 8. |
- Höglund, Solveig, et al.
(författare)
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Willow resistance to a galling insect is driven by a lack of induced susceptibility not an induced defense
- 2015
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Ingår i: Arthropod-Plant Interactions. - : Springer Science and Business Media LLC. - 1872-8855 .- 1872-8847. ; 9, s. 447-455
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Tidskriftsartikel (refereegranskat)abstract
- Gall-forming insects need to manipulate host plant's growth to access food resources. Because of this intimate relationship, a hypersensitive response (HR) is thought to be an important plant defense mechanism to kill the insect before a gall is formed. Few data exist, however, that unambiguously demonstrate that HR is causally linked to resistance against galling insects. Variation in Salix viminalis resistance to the gall midge Dasineura marginemtorquens is governed by only a few genes. Although the HR is considered to be an important resistance mechanism, an earlier study based on quantitative trait locus (QTL) analysis of data sets in which resistance was expressed, has shown that larval mortality is related to a single locus in a genomic region that does not contain a locus for HR, thus challenging previous suppositions that resistance is causally linked to the expression of a HR. The present study aims to test whether or not a HR causes the observed variation in willow resistance to D. marginemtorquens. By increasing the number of markers in the genomic region of interest and reanalyzing the QTL, we have enhanced the level of resolution, so permitting a more conclusive analysis than has previously been possible. The analysis identifies two genomic regions responding to gall midge attack. Importantly, the locus for resistance (measured as neonate larval mortality) and the locus for the HR are located in different regions, strongly contradicting the induced defense hypothesis. The analysis found that resistance and susceptibility were highly correlated because the allele associated with resistance was also associated with an absence of galls. It is suggested that a lack of induced susceptibility, rather than induced defense, explains the 'resistance' of S. viminalis to D. marginemtorquens.
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