| 1. |
- Hjältén, Joakim, et al.
(författare)
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Variable responses of natural enemies to Salix triandra phenotypes with different secondary chemistry
- 2007
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Ingår i: Oikos. - : Wiley-Blackwell. - 0030-1299 .- 1600-0706. ; 116:5, s. 751-758
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Tidskriftsartikel (refereegranskat)abstract
- Plant phenotypes often differ in their resistance to natural enemies, but the mechanism for this has seldom been identified. The aim of this study was to determine if the spatial patterns of phenotype use of a highly specialized insect herbivore (the galling sawfly Pontania triandrae) in a natural willow population can be related to phenotypic variation in plant secondary chemistry. Furthermore, we tested if traits that confer resistance to one type of natural enemy, i.e. the galling sawfly, also confer resistance to others, in our case a leaf beetle Gonioctena linnaeana and the rust fungus Melampsora amygdalinae. We identified 18 phenotypes with high and 18 phenotypes with low gall density in our field population and determined gall densities, the degree of leaf damage and rust infection on each phenotype and collected leaves for chemical analyses. The concentration of phenolics was higher in phenotypes with high density of galls suggesting that this galling sawfly may use phenolics as oviposition cues. Rust infection showed the opposite pattern, with lower levels on clones with high concentration of phenolics, while leaf damage by G. linnaeana did not differ between clone types. This indicates that these important natural enemies may assert divergent selection on willow phenotypes and that this might provide a mechanism for maintaining phenotypic variation within willow populations.
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| 2. |
- Landström, Lena, 1962-
(författare)
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Åklagaren som grindvakt : En rättsvetenskaplig studie av åklagarens befogenheter vid utredning och åtal av brott
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In Sweden an oral hearing, the trial, is held as the ideal model for the criminal procedure and according to the legality principle reported crimes ought to be investigated and prosecuted. Over time high levels of reported crimes have led to an increase in pressure on the courts and other actors in the criminal process. This pressure has created new ways of dealing with reported crimes in summary procedures and to exceptions from the legality principle. Such changes have given the prosecutor a key role in deciding how cases are dealt with in the criminal process. The purpose of this thesis is to examine the Swedish public prosecutor’s influence on the choice of cases that are investigated, prosecuted and tried in court during a trial. The study examines the prosecutors’ legal authority and how that authority has changed from the time that the Code of Judicial Procedure came into force in 1948 to the beginning of 2011.A starting point for the examination is that investigating, prosecuting and trying cases in the criminal process should be carried out in a way that is considered to be fair according to societal values, which are embedded in the legal system. Both decisions about which cases will be tried and the procedure involved in how to try them has to be performed in a way that seems to be fair. In the study the values that underlie the criminal process is examined through a model. This model assumes that the criminal process has been created and developed to satisfy different requirements, which can be separated into three main groups: the functions of the criminal process, legal principles and the main objectives of a good administration of justice. The model is used to analyze and discuss the development of the legal rules.The prosecutor’s authority and influence over the process has broadened and the use of summary procedures has served to place the focus on the police investigation instead of the trial. Among the objectives of a good administration of justice Speed and Cost effectiveness are considered to be more important than Security. As long as the Trust in the system is sufficient this development can continue. A conclusion from the study is that there is a need for some actor to prioritize and to do that openly. In the study the issue is raised whether it is time to question the legality principle as the main principle for the Swedish legal system.
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| 3. |
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| 4. |
- Niemi, Lena, et al.
(författare)
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Insect feeding preferences and plant phenolic glucosides in the system Gonioctena linnaeana-Salix triandra
- 2005
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Ingår i: Entomologia Experimentalis et Applicata. - Amsterdam : North-Holland Pub. Co.. - 0013-8703 .- 1570-7458. ; 115:1, s. 61-66
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate the preference of a leaf beetle to different Salix clones, and to relate this preference to plant chemistry. The preference of Gonioctena linnaeana Schrank (Coleoptera: Chrysomelidae) was tested in cafeteria experiments using its host Salix triandra L. (Salicaeae) from three Swedish isolated populations and one Russian population from the main distribution range of the host. The leaves from the different host clones were used to analyse the content of phenolic glucosides and the amount of condensed tannins. The larvae did not show any feeding preferences for host clones from the population they originated from, but all Swedish host populations were preferred over the Russian host population. This suggests a preference for regional hosts. We analyzed whether leaf chemistry parameters may explain host plant preferences. Chemical analysis of the leaves showed that the quantities, but not the quality, of the phenolic compounds differed between populations. A Principal Component Analysis of the chemical data also highlighted a difference between the Swedish and Russian host plant populations. The two most important compounds separating Russian from Swedish clones were gallocatechin and salidroside. However, the difference in preference could also be a result of, for example, nutritional quality, water content, or leaf texture. The relative importance of these different factors should be evaluated in future experiments.
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| 5. |
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| 6. |
- Niemi, Lena, 1963-
(författare)
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Spatial patterns in the interaction between Salix triandra and associated parasites
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on mechanisms and processes underlying spatial patterns of resistance and virulence and on local adaptations in plant–parasite interactions. The model system used comprises the plant host Salix triandra, the pathogenic rust fungus Melampsora amygdalinae, the leaf beetle Gonioctena linnaeana, and the galler Pontania triandrae. In this work, I (1) emphasize the most important factors determining the outcome of a plant–pathogen interaction, and the types of systems in which local adaptations can be expected, (2) examine the resistance structures of different populations of S. triandra, and whether the leaf beetle G. linnaeana responds to the local conditions of the populations of S. triandra in Sweden, and (3) address whether the distribution of parasites on S. triandra can be explained by the plant content of secondary metabolites.A review of several studies of the subject leads to the conclusion that adaptation of pathogens to their local hosts is more likely to be found in systems in which the pathogen is host-specific, non-systemic, and has a larger dispersal range and evolutionary potential than its host does. Furthermore, the scale of the study must be adjusted to that of the pathogen’s local population distribution. In addition, the temporary nature of host–pathogen interactions influences the importance of sample size, and too-small sample sizes can lower the chance of finding local adaptations, even though they may have evolved in a given system. The results of an inoculation experiment using material from physically isolated natural populations of S. triandra and M. amygdalinae confirm the importance of previous conclusions.Spatial variation in the resistance structure of S. triandra also has effects on the insect herbivore G. linnaeana, which has responded by adapting to the local hosts. However, local differences in secondary chemistry affect different parasites in different ways, and while P. triandrae is attracted by high levels of phenolic compounds, including tannins, M. amygdalinae and G. linnaeana are more rarely found on plant individuals with high concentrations of tannins. In addition, brood deposition by adult females of G. linnaeana and the performance of larvae are positively affected by luteolin-7-glucoside and an additional unidentified flavonoid, whereas they are negatively affected by the presence of (+)-catechin and high levels of tannins.Our results also show that plants traits that provide resistance to one type of parasite do not necessarily provide resistance to others. This indicates that different natural enemies potentially assert divergent selection pressure on S. triandra phenotypes which can be important for maintaining phenotypic variation in plant species.
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| 7. |
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| 8. |
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| 9. |
- Wennström, Anders, et al.
(författare)
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Mother really knows best : host choice of adult phytophagous insect females reflects a within-host variation in suitability as larval food
- 2010
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Ingår i: Chemoecology. - Basel : Birkhauser. - 0937-7409 .- 1423-0445. ; 20:1, s. 35-42
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Tidskriftsartikel (refereegranskat)abstract
- Non-random distribution patterns of specialized phytophagous insects on their hosts may depend on intraspecific differences in plant tissue quality, including nutrients and secondary compounds. Secondary compounds are involved in plant resistance, but are also important for the recognition and acceptability of plants as resources by specialized insects. If individuals within a plant species vary in their content of such secondary substances, there may also be qualitative differences between them. In such cases, natural selection will favor insects with the ability to distinguish and prefer the more suitable plants. In Sweden, the leaf beetle Gonioctena linnaeana Schrank (Coleoptera, Chrysomelidae) is highly specialized on one host, the native willow Salix triandra L (Salicaceae). Field observations reveal that some host plants in a population harbor many feeding larvae, causing severe defoliation, whereas neighboring plants may have few or no feeding larvae. Our hypothesis is that the distribution pattern of G. linnaeana larvae in this population results from qualitative differences between individual host plants in combination with the ability of G. linnaeana females to distinguish between plants that are suitable and not suitable for offspring performance. We examine whether larval survival differs depending on diet and whether the content of secondary chemical compounds explains female preference. Based on the higher survival rate of larvae reared on leaves from preferred hosts, we conclude that G. linnaeana females have evolved a behavior that maximizes offspring performance and thus positively affects female fitness. A chemical survey of the plants indicates that luteolin-7-glucoside and an unidentified flavonoid are important for separating the preferred from the non-preferred plants.
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| 10. |
- Niemi, MEK, et al.
(författare)
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- 2021
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swepub:Mat__t
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