Umeå University's logo

umu.sePublications
Change search
Refine search result
1 - 14 of 14
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Axelsson, E. Petter
    et al.
    Hjalten, Joakim
    LeRoy, Carri J.
    Whitham, Thomas G.
    Julkunen-Tiitto, Riitta
    Wennström, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Leaf litter from insect-resistant transgenic trees causes changes in aquatic insect community composition2011In: Journal of Applied Ecology, ISSN 0021-8901, E-ISSN 1365-2664, Vol. 48, no 6, p. 1472-1479Article in journal (Refereed)
    Abstract [en]

    1. Recent research has addressed how transgenic residues fromarable crops may influence adjacent waterways, aquatic consumers and important ecosystem processes such as litter breakdown rates. With future applications of transgenic plants in forestry, such concerns may apply to forest stream ecosystems. Before any large-scale release of genetically modified (GM) trees, it is therefore imperative to evaluate the effects of genetic modifications in trees on such ecosystems. 2. We conducted decomposition experiments under natural stream conditions using leaf litter from greenhouse grown GM trees (Populus tremula x Populus tremuloides) that express Bacillus thuringiensis (Bt) toxins (cry3Aa; targeting coleopteran leaf-feeding beetles) to examine the hypothesis that GM trees would affect litter decomposition rates and/or the aquatic arthropod community that colonizes and feeds on leaf litter in streams. 3. We show that two independent transformations of isogenic Populus trees to express Bt toxins caused similar changes to the composition of aquatic insects colonizing the leaf litter, ultimately manifested in a 25% and 33% increases in average insect abundance. 4. Measurements of 24 phenolic compounds as well as nitrogen (N) and carbon (C) in the litter did not significantly differ among modified and wild-type trees and were thus not sufficient to explain these differences in the insect assemblage. 5. Decomposition rates were comparable among litter treatments suggesting that the normal suite of leaf traits influencing decomposition was similar among litter treatments and that the shredding functions of the community were maintained despite the changes in insect community composition. 6. Synthesis and applications. We report that leaf litter from GM trees affected the composition of aquatic insect communities that colonized litter under natural stream conditions. This suggests that forest management using GM trees may affect adjacent waterways in unanticipated ways, which should be considered in future commercial applications of GM trees. We also argue that studies at different scales (e.g. species, communities and ecosystems) will be needed for a full understanding of the environmental effects of Bt plants.

  • 2. Axelsson, E. Petter
    et al.
    Hjalten, Joakim
    Whitham, Thomas G.
    Julkunen-Tiitto, Riitta
    Pilate, Gilles
    Wennström, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Leaf ontogeny interacts with Bt modification to affect innate resistance in GM aspens2011In: Chemoecology, ISSN 0937-7409, E-ISSN 1423-0445, Vol. 21, no 3, p. 161-169Article in journal (Refereed)
    Abstract [en]

    Bioassays with a non-target slug (Deroceras spp.) and chemical analyses were conducted using leaf tissue from already existing genetically modified insect-resistant aspen trees to examine whether genetic modifications to produce Bacillus thuringiensis (Bt) toxins could affect plant phytochemistry, which in turn might influence plant-herbivore interactions. Three major patterns emerged. First, two independent modifications for Bt resistance affected the phytochemical profiles of leaves such that both were different from the isogenic wild-type (Wt) control leaves, but also different from each other. Among the contributors to these differences are substances with a presumed involvement in resistance, such as salicortin and soluble condensed tannins. Second, bioassays with one Bt line suggest that the modification somehow affected innate resistance ("Innate" is used here in opposition to the "acquired" Bt resistance) in ways such that slugs preferred Bt over Wt leaves. Third, the preference test suggests that the innate resistance in Bt relative to Wt plants may not be uniformly expressed throughout the whole plant and that leaf ontogeny interacts with the modification to affect resistance. This was manifested through an ontogenetic determined increase in leaf consumption that was more than four times higher in Bt compared to Wt leaves. Our result are of principal importance, as these indicate that genetic modifications can affect innate resistance and thus non-target herbivores in ways that may have commercial and/or environmental consequences. The finding of a modification-ontogeny interaction effect on innate resistance may be especially important in assessments of GM plants with a long lifespan such as trees.

  • 3. Axelsson, E Petter
    et al.
    Hjältén, Joakim
    LeRoy, Carri J
    Julkunen-Tiitto, Riitta
    Wennström, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Pilate, Gilles
    Can leaf litter from genetically modified trees affect aquatic ecosystems?2010In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 13, no 7, p. 1049-1059Article in journal (Refereed)
    Abstract [en]

    In addition to potential benefits, biotechnology in silviculture may also be associated with environmental considerations, including effects on organisms associated with the living tree and on ecosystems and processes dependent on tree residue. We examined whether genetic modification of lignin characteristics (CAD and COMT) in Populus sp. affected leaf litter quality, the decomposition of leaf litter, and the assemblages of aquatic insects colonizing the litter in three natural streams. The decomposition of leaf litter from one of the genetically modified (GM) lines (CAD) was affected in ways that were comparable over streams and harvest dates. After 84 days in streams, CAD-litter had lost approximately 6.1% less mass than the non-GM litter. Genetic modification also affected the concentration of phenolics and carbon in the litter but this only partially explained the decomposition differences, suggesting that other factors were also involved. Insect community analyses comparing GM and non-GM litter showed no significant differences, and the two GM litters showed differences only in the 84-day litterbags. The total abundance and species richness of insects were also similar on GM and non-GM litter. The results presented here suggest that genetic modifications in trees can influence litter quality and thus have a potential to generate effects that can cross ecosystem boundaries and influence ecosystem processes not directly associated with the tree. Overall, the realized ecological effects of the GM tree varieties used here were nevertheless shown to be relatively small.

  • 4.
    Blomberg, Patrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Wennström, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hjältén, Joakim
    Lindau, Anna
    Ericson, Lars
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Genetically engineered aspen (Populus tremula x tremuloides) alters its interactions with the non-target pathogen Venturia tremulaeManuscript (preprint) (Other academic)
  • 5. Hjalten , J.
    et al.
    Lindau , A.
    Wennstrom , Anders
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Blomberg , Patrik
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Witzell , J.
    Ericson , Lars
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Vole response to unintentional changes in the chemistry of GM poplars (Chemoecology (2008) 14, (227-232) DOI 10.007/s00049-008-0409-0)2008In: Chemoecology, ISSN 0937-7409, E-ISSN 1423-0445, Vol. 18, no 4, p. 263-Article in journal (Refereed)
  • 6. Hjalten, Joakim
    et al.
    Axelsson, E. Petter
    Julkunen-Tiitto, Riitta
    Wennström, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Pilate, Gilles
    Innate and Introduced Resistance Traits in Genetically Modified Aspen Trees and Their Effect on Leaf Beetle Feeding2013In: PLOS ONE, E-ISSN 1932-6203, Vol. 8, no 9, p. e73819-Article in journal (Refereed)
    Abstract [en]

    Genetic modifications of trees may provide many benefits, e. g. increase production, and mitigate climate change and herbivore impacts on forests. However, genetic modifications sometimes result in unintended effects on innate traits involved in plant-herbivore interactions. The importance of intentional changes in plant defence relative to unintentional changes and the natural variation among clones used in forestry has not been evaluated. By a combination of biochemical measurements and bioassays we investigated if insect feeding on GM aspens is more affected by intentional (induction Bt toxins) than of unintentional, non-target changes or clonal differences in innate plant defence. We used two hybrid wildtype clones (Populus tremula x P. tremuloides and Populus tremula x P. alba) of aspen that have been genetically modified for 1) insect resistance (two Bt lines) or 2) reduced lignin properties (two lines COMT and CAD), respectively. Our measurements of biochemical properties suggest that unintended changes by GM modifications (occurring due to events in the transformation process) in innate plant defence (phenolic compounds) were generally smaller but fundamentally different than differences seen among different wildtype clones (e. g. quantitative and qualitative, respectively). However, neither clonal differences between the two wildtype clones nor unintended changes in phytochemistry influenced consumption by the leaf beetle (Phratora vitellinae). By contrast, Bt induction had a strong direct intended effect as well as a post experiment effect on leaf beetle consumption. The latter suggested lasting reduction of beetle fitness following Bt exposure that is likely due to intestinal damage suffered by the initial Bt exposure. We conclude that Bt induction clearly have intended effects on a target species. Furthermore, the effect of unintended changes in innate plant defence traits, when they occur, are context dependent and have in comparison to Bt induction probably less pronounced effect on targeted herbivores.

    Download full text (pdf)
    fulltext
  • 7. Hjälten, J.
    et al.
    Lindau, A.
    Wennström, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Blomberg, Patrik
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Witzell, J.
    Hurry, V.
    Ericson, Lars
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Moritz, T.
    Karlsson, Jan
    Vole response to unintentional changes in the chemistry of GM poplars2008In: Chemoecology, Vol. 180, no 4, p. 227-231Article in journal (Refereed)
    Abstract [en]

    There is an increased interest for the use of GM trees in forestry and several commercially promising lines are now available. However, the ecological implications of the use of GM trees, e.g. effects on non-target natural enemies, have rarely been explored. The aim of this study was to determine if modification of non-defensive traits in GM poplars unintentionally can influence plant chemistry in a way that has consequences for palatability to voles. In a greenhouse experiment, we used two lines, SPS33A and SPS26, of GM hybrid poplars (Populus tremula x tremuloides) with 1.5 and 4 times, respectively, over-expression sucrose-phosphate synthase (SPS). This enzyme plays a central role in sucrose synthesis, affecting cold acclimation, mesophyll sucrose content and biomass production. As a control we used the isogenic unmodified wild type. Stems of these poplars were presented to bank voles and field voles in cafeteria experiments. The concentration of condensed tannins was higher in leaves of lines SPS33A and SPS26 than in the isogenic wild-type and the concentration of nitrogen was higher in line SPS33A than in both the wild-type and line SPS26. Although the bank voles consumed slightly less bark from SPS33A, there were no significant differences in the preference of bank vole or field vole for the different poplar lines. This indicates that the changes in plant chemistry were insufficient to produce any strong herbivore response or that alteration in tannins and nitrogen counteracted each other. Still, changes in the interactions between mammalian herbivores and GM trees are important to consider in future cost-benefits analyses of GM trees.

  • 8.
    Hjältén, Joakim
    et al.
    SLU, Umeå.
    Axelsson, E Petter
    SLU, Umeå.
    Whitham, Thomas G
    Arizona, United States of America.
    LeRoy, Carri J
    Washington, United States of America.
    Julkunen-Tiitto, Riitta
    Joensuu, Finland.
    Wennström, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Pilate, Gilles
    Orle´ans, France.
    Increased Resistance of Bt Aspens to Phratora vitellinae (Coleoptera) Leads to Increased Plant Growth under Experimental Conditions2012In: PLOS ONE, E-ISSN 1932-6203, Vol. 7, no 1, article id e30640Article in journal (Refereed)
    Abstract [en]

    One main aim with genetic modification (GM) of trees is to produce plants that are resistant to various types of pests. The effectiveness of GM-introduced toxins against specific pest species on trees has been shown in the laboratory. However, few attempts have been made to determine if the production of these toxins and reduced herbivory will translate into increased tree productivity. We established an experiment with two lines of potted aspens (Populus tremulaxPopulus tremuloides) which express Bt (Bacillus thuringiensis) toxins and the isogenic wildtype (Wt) in the lab. The goal was to explore how experimentally controlled levels of a targeted leaf beetle Phratora vitellinae (Coleoptera; Chrysomelidae) influenced leaf damage severity, leaf beetle performance and the growth of aspen. Four patterns emerged. Firstly, we found clear evidence that Bt toxins reduce leaf damage. The damage on the Bt lines was significantly lower than for the Wt line in high and low herbivory treatment, respectively. Secondly, Bt toxins had a significant negative effect on leaf beetle survival. Thirdly, the significant decrease in height of the Wt line with increasing herbivory and the relative increase in height of one of the Bt lines compared with the Wt line in the presence of herbivores suggest that this also might translate into increased biomass production of Bt trees. This realized benefit was context-dependent and is likely to be manifested only if herbivore pressure is sufficiently high. However, these herbivore induced patterns did not translate into significant affect on biomass, instead one Bt line overall produced less biomass than the Wt. Fourthly, compiled results suggest that the growth reduction in one Bt line as indicated here is likely due to events in the transformation process and that a hypothesized cost of producing Bt toxins is of subordinate significance.

    Download full text (pdf)
    fulltext
  • 9. Hjältén, Joakim
    et al.
    Lindau, Anna
    Wennström, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Blomberg, Patrik
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Witzell, Johanna
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Ericson, Lars
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Unintentional changes of defence traits in GM trees can influence plant-herbivore interactions2007In: Basic and Applied Ecology, Vol. 8, no 3, p. 434-443Article in journal (Refereed)
    Abstract [en]

    GM trees hold promises of increased quality and yield and reduced use of herbicides and pesticides but could also have ecological consequences. We investigated whether modification of a non-defensive trait unintentionally influenced plant traits important for plant-herbivore interactions. We found that over-expression of sucrose phosphate synthase (SPS), which is known to increase mesophyll sucrose content and biomass production in GM aspens, also unintentionally induced changes in the concentration of plant phenolics and nitrogen. One of the GM lines, SPS33A, had higher concentrations of salicin, tremuloidin, condensed tannins and nitrogen and lower concentrations of coumaric acid and four flavonoids compared with the isogenic wild type. Line SPS33A was also utilized less by the leaf-beetle Phratora vitellinae than the isogenic wild type. Ecological consequences such as this are not specific to GM trees or GM plants but can occur as a result of the introduction of all introduced new varieties of crops or trees. Nevertheless, the results underline the need to consider these unexpected effects when evaluating both the potential benefits and the potential risks with GM plants, and highlight the need to establish and implement comprehensive product-by-product evaluation protocols for GM plants.

  • 10. Hjältén, Joakim
    et al.
    Niemi, Lena
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Wennström, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ericson, Lars
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Roininen, Heikki
    Julkunen-Tiitto, Riitta
    Variable responses of natural enemies to Salix triandra phenotypes with different secondary chemistry2007In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 116, no 5, p. 751-758Article in journal (Refereed)
    Abstract [en]

    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.

  • 11.
    Niemi, Lena
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Wennström, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Can adaptation of parasitic fungi to their local host plants be a general expectation?Manuscript (preprint) (Other academic)
  • 12.
    Niemi, Lena
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Wennström, Anders
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Hjältén, Joakim
    Ericson, Lars
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Preference and performance of the leaf-eating beetle Gonioctena linnaeana on sympatric and allopatric populations of Salix triandraManuscript (preprint) (Other academic)
  • 13.
    Wennström, Anders
    Umeå University.
    Systemic fungal diseases in natural plant populations1993Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The purpose of this thesis was to study interactions between systemic fungal diseases and perennial plants. Using the systemic rust Puccinia minussensis on the host plant Lactuca sibirica, and the rust Puccinia pulsatillae on the host plant Pulsatilla pratensis, this thesis focused on: (i) the effects of systemic diseases on their hosts (ii) host and pathogen responses to abiotic factors, (iii) the importance of life history strategies for understanding host-pathogen interactions, and (iv) the evolutionary consequences of living in close associations.

    Results of greenhouse experiments showed that Lactuca sibirica had a high plasticity in growth, since it produced significantly more shoots in favourable than in unfavourable growth conditions. Both the disease levels and the number of healthy shoots (i.e. escape) were significantly higher under favourable conditions. Disease spread within the rhizome was found to be incomplete, and the risk of aecidial- infection decreased with distance from the parent. Furthermore, one isolate of the fungus had highest success and reduced the host plant biomass and shoot production more on the clone it was collected on compared to four other clones .

    In the field, disease levels were found to fluctuate more at localities subjected to disturbance, the host and pathogen abundances were found to be in phase and the pathogen showed no delayed response to increasing host densities. The rust Puccinia pulsatillae on Pulsatilla pratensis showed no fluctuations between years, low infection rates, and disease levels were higher in ungrazed compared to grazed sites. There was no escape from the disease in this system.

    A comparison of characteristics of different systemic fungi and hosts with different growth patterns indicated that the life history strategies of both host plants and pathogens need to be studied if the long-term consequences of host-pathogen interactions are to be predicted.

    Download full text (pdf)
    fulltext
  • 14.
    Wennström, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Niemi Hjulström, Lena
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hjältén, Joakim
    Julkunen-Tiitto, Riitta
    Mother really knows best: host choice of adult phytophagous insect females reflects a within-host variation in suitability as larval food2010In: Chemoecology, ISSN 0937-7409, E-ISSN 1423-0445, Vol. 20, no 1, p. 35-42Article in journal (Refereed)
    Abstract [en]

    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.

1 - 14 of 14
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf