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  • 1.
    Albrectsen, Benedicte R.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lundberg, Per
    Nutrient addition extends flowering display, which gets tracked by seed predators, but not by their parasitoids2008Ingår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 117, s. 473-480Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Although phenological matching between two and three trophic interactions has received some attention, it has largely been disregarded in explaining the lack of strong cascade dynamics in terrestrial systems. We studied the response of the specialist seed predator, Paroxyna plantaginis (Tephritidae) and associated generalist parasitoids (Chalcidoidea) to controlled fertilisation of individuals of naturally growing Tripolium vulgare (Asteraceae) on four island populations (Skeppsvik Archipelago, Sweden). We consistently found evidence of nutrient limitation: fertilised plants increased their biomass, produced more capitula (the oviposition units for tephritid flies), were more at risk of attack by the tephritids, and puparia were heavier in fertilised plants. During some parts of the season tephritids became more heavily parasitized, supporting the presence of cascade dynamics, however net parasitism over season decreased in response to nutrient addition. We found no evidence that capitulum size complicated parasitoid access to the tephritids, however the extended bud production prolonged the flowering season. Thus, tephritids utilized the surplus production of capitula throughout the entire season, while parasitoids did not expand their oviposition time window accordingly. Implications for top down regulation and cascade dynamics in the system are discussed.

  • 2. Berglund, H
    et al.
    Edman, M
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Ericson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Temporal variation in wood-fungi diversity in boreal old-growth forests: implications for monitoring2005Ingår i: Ecological Applications, Vol. 15, s. 970-982Artikel i tidskrift (Refereegranskat)
  • 3.
    Berglund, Håkan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Ekologi och geovetenskap.
    Edman, Mattias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Ekologi och geovetenskap.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Ekologi och geovetenskap.
    Temporal variation of wood-fungi diversity in boreal old-growth forests: implications for monitoring2005Ingår i: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 15, nr 3, s. 970-982Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Monitoring programs that supply reliable and sufficient information on numbers and types of organisms are essential for following changes in biodiversity. In boreal Fennoscandia, forest-dwelling species are threatened in managed forest landscapes and, thus, are of particular concern for conservation strategies. Wood fungi represent key ecological components in the boreal forest that are sensitive to forestry and widely used as indicators in large-scale forest inventories for identifying valuable forest habitats. Knowledge of their natural dynamics is required for designing monitoring programs to assess the adequacy of conservation strategies. We studied the occurrence of corticoids (Corticiaceae) and polypores (Polyporaceae) over time at different spatial scales in unexploited boreal old-growth forests. Data from 70 downed logs followed during an eight-year period showed that the lifespan of fruit bodies of most species was shorter than four years. Even perennial species followed this pattern, although fruit bodies of some species (e.g., Phellinus spp.) remained vital throughout the eight years studied. Both species richness and species composition on individual logs changed markedly over the eight years due to deterministic succession of species paralleling the wood decay. By contrast, data from the stand scale, i.e., seven 0.1 -ha plots, showed that species richness and species composition of polypores did not undergo any major changes during a six-year period. A majority of all recorded polypore species (80%) were already present at the first inventory. However, although species richness remained constant at the stand scale, corticoid species composition differed between years, reflecting their short-lived, annual fruit bodies. This study suggests that monitoring should be performed at stand scale and focus on species with durable fruit bodies, e.g., polypores. This will provide data that can be used both to detect future changes in biodiversity in old-growth spruce forests and to evaluate conservation strategies.

  • 4.
    Bidleman, Terry F.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Brugel, Sonia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Haglund, Peter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kupryianchyk, Darya
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lau, Danny C. P.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Liljelind, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lundin, Lisa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Tysklind, Anders
    Tysklind, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Bromoanisoles and Methoxylated Bromodiphenyl Ethers in Macroalgae from Nordic Coastal Regions2019Ingår i: Environmental Science: Processes & Impacts, ISSN 2050-7887, E-ISSN 2050-7895, s. 881-892Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Marine macroalgae are used worldwide for human consumption, animal feed, cosmetics and agriculture. In addition to beneficial nutrients, macroalgae contain halogenated natural products (HNPs), some of which have toxic properties similar to those of well-known anthropogenic contaminants. Sixteen species of red, green and brown macroalgae were collected in 2017–2018 from coastal waters of the northern Baltic Sea, Sweden Atlantic and Norway Atlantic, and analyzed for bromoanisoles (BAs) and methoxylated bromodiphenyl ethers (MeO-BDEs). Target compounds were quantified by gas chromatography-low resolution mass spectrometry (GC-LRMS), with qualitative confirmation in selected species by GC-high resolution mass spectrometry (GC-HRMS). Quantified compounds were 2,4-diBA, 2,4,6-triBA, 2′-MeO-BDE68, 6-MeO-BDE47, and two tribromo-MeO-BDEs and one tetrabromo-MeO-BDE with unknown bromine substituent positions. Semiquantitative results for pentabromo-MeO-BDEs were also obtained for a few species by GC-HRMS. Three extraction methods were compared; soaking in methanol, soaking in methanol–dichloromethane, and blending with mixed solvents. Extraction yields of BAs did not differ significantly (p > 0.05) with the three methods and the two soaking methods gave equivalent yields of MeO-BDEs. Extraction efficiencies of MeO-BDEs were significantly lower using the blend method (p < 0.05). For reasons of simplicity and efficiency, the soaking methods are preferred. Concentrations varied by orders of magnitude among species: ∑2BAs 57 to 57 700 and ∑5MeO-BDEs < 10 to 476 pg g−1 wet weight (ww). Macroalgae standing out with ∑2BAs >1000 pg g−1 ww were Ascophyllum nodosumCeramium tenuicorneCeramium virgatumFucus radicansFucus serratusFucus vesiculosusSaccharina latissimaLaminaria digitata, and Acrosiphonia/Spongomorpha sp. Species A. nodosumC. tenuicorneChara virgataF. radicans and F. vesiculosus (Sweden Atlantic only) had ∑5MeO-BDEs >100 pg g−1ww. Profiles of individual compounds showed distinct differences among species and locations.

  • 5. Burdon , JJ
    et al.
    Thrall , PH
    Ericson , Lars
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Plant Pathogens and Disease: Newly Emerging Diseases2009Ingår i: Encyclopedia of Microbiology, Oxford: Elsevier , 2009, s. 647-654Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 6.
    Burdon, Jeremy J.
    et al.
    CSIRO-Plant Industry, Canberra, Australia.
    Thrall, Peter H.
    CSIRO-Plant Industry, Canberra, Australia.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Genes, communities & invasive species: understanding the ecological and evolutionary dynamics of host-pathogen interactions2013Ingår i: Current opinion in plant biology, ISSN 1369-5266, E-ISSN 1879-0356, Vol. 16, nr 4, s. 400-405Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Reciprocal interactions between hosts and pathogens drive ecological, epidemiological and co-evolutionary trajectories, resulting in complex patterns of diversity at population, species and community levels. Recent results confirm the importance of negative frequency-dependent rather than 'arms-race' processes in the evolution of individual host-pathogen associations. At the community level, complex relationships between species abundance and diversity dampen or alter pathogen impacts. Invasive pathogens challenge these controls reflecting the earliest stages of evolutionary associations (akin to arms-race) where disease effects may be so great that they overwhelm the host's and community's ability to respond. Viewing these different stabilization/destabilization phases as a continuum provides a valuable perspective to assessment of the role of genetics and ecology in the dynamics of both natural and invasive host-pathogen associations.

  • 7.
    Burdon, Jeremy J.
    et al.
    CSIRO-Plant Industry, Canberra, Australia.
    Thrall, Peter H.
    CSIRO-Plant Industry, Canberra, Australia.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    The current and future dynamics of disease in plant communities2006Ingår i: Annual Review of Phytopathology, ISSN 0066-4286, E-ISSN 1545-2107, Vol. 44, s. 19-39Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pathogens are powerful evolutionary forces shaping the structure and dynamics of both individual species and of the communities of which they are part, at a broad range of genetic, ecological, spatial, and temporal scales. At all these levels their impact varies from the subtle and little recognized through to the most obvious destruction. Today the direct role of pathogens in natural plant communities is better recognized than at previous times, although the nuances of their interactions and the cascade of ramifications that can flow through changing biotic and abiotic effects are only now gaining recognition. However, as human influence on pathogens increases either directly through enhanced if accidental dispersal, or through anthropogenic impacts on climate-we may expect to see increasing evidence of pathogens affecting plant species, community structure, and ecosystem function.

  • 8. Burdon, J.J.
    et al.
    Ericson, Lars E.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Thrall, P.H.
    Emerging plant diseases2014Ingår i: Encyclopedia of agriculture and food systems: volume 3 / [ed] Neal K. Van Alfen, San Diego: Academic Press, 2014, 2, s. 59-67Kapitel i bok, del av antologi (Refereegranskat)
  • 9.
    Carlsson-Granér, Ulla
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Giles, Barbara E.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Plant disease and islands2009Ingår i: Encyclopedia of Islands / [ed] Rosemary G. Gillespie and David A. Clague, University of California Press , 2009, s. 748-752Kapitel i bok, del av antologi (Refereegranskat)
  • 10. Chauvet, S
    et al.
    van der Velde, M
    Imbert, E
    Guillemin, M L
    Mayol, M
    Riba, M
    Smulders, M J M
    Vosman, B
    Ericson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Bijlsma, R
    Giles, B E
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    The effects of colonization and migration for variation in the selfing wind-dispersed species2004Ingår i: Mol Ecol, ISSN 0962-1083, Vol. 13, s. 1391-1407Artikel i tidskrift (Refereegranskat)
  • 11. Chauvet, S
    et al.
    van der Velde, M
    Imbert, E
    Guillemin, ML
    Mayol, M
    Riba, M
    Smulders, MJM
    Vosman, B
    Ericson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Bijlsma, R
    Giles, BE
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Past and current gene flow in the selfing wind-dispersed species Mycelis muralis in western Europe2004Ingår i: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 13, nr 6, s. 1391-1407Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The distribution of genetic diversity in Mycelis muralis, or wall lettuce, was investigated at a European scale using 12 microsatellite markers to infer historical and contemporary forces from genetic patterns. Mycelis muralis has the potential for long-distance seed dispersal by wind, is mainly self-pollinated, and has patchily distributed populations, some of which may show metapopulation dynamics. A total of 359 individuals were sampled from 17 populations located in three regions, designated southern Europe (Spain and France), the Netherlands, and Sweden. At this within-region scale, contemporary evolutionary forces (selfing and metapopulation dynamics) are responsible for high differentiation between populations (0.34 < FST < 0.60) but, contrary to expectation, levels of within-population diversity, estimated by Nei's unbiased expected heterozygosity (HE) (0.24 < HE < 0.68) or analyses of molecular variance (50% of the variation found within-populations), were not low. We suggest that the latter results, which are unusual in selfing species, arise from efficient seed dispersal that counteracts population turnover and thus maintains genetic diversity within populations. At the European scale, northern regions showed lower allelic richness (A = 2.38) than populations from southern Europe (A = 3.34). In light of postglacial colonization hypotheses, these results suggest that rare alleles may have been lost during recolonization northwards. Our results further suggest that mutation has contributed to genetic differentiation between southern and northern Europe, and that Sweden may have been colonized by dispersers originating from at least two different refugia.

  • 12.
    Edman, M
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Gustafsson, G
    Stenlid, J
    Ericson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Abundance and viability of fungal spores along a forestry gradient - responses to habitat loss and isolation?2004Ingår i: Oikos, Vol. 104, s. 35-42Artikel i tidskrift (Refereegranskat)
  • 13.
    Edman, M
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Gustafsson, G
    Stenlid, J
    Jonsson, B
    Ericson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Spore deposition of wood-decaying fungi: importance of landscape composition2004Ingår i: Ecography, Vol. 27, s. 103-111Artikel i tidskrift (Refereegranskat)
  • 14. Edman, M
    et al.
    Moller, R
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Effects of enhanced tree growth rate on the decay capacities of three saprotrophic wood-fungi2006Ingår i: Forest Ecology and Management, Vol. 232, s. 12-18Artikel i tidskrift (Refereegranskat)
  • 15.
    Ericson , Lars
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Burdon , JJ
    Linking field epidemiological and individual plant resistance patterns in the Betula pubescens-Melampsoridium betulinum host-pathogen interaction2009Ingår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 118, s. 225-232Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Over a period of seven seasons (1995-2001 inclusively) four distinct epidemics of the rust pathogen Melampsoridium betulinum were recorded in stands of Betula pubescens. During those epidemics, host plants incurred varying levels of disease severity. Some individuals suffered high levels on all occasions; some low; while yet others were either intermediately affected or showed variable disease severity from season to season. Tests of pathotypic differences among 33 isolates of M. betulinum collected from six sites found a broad range of pathotypes ranging from highly virulent to highly avirulent. Similarly a random sample of 40 B. pubescens lines from one site showed a wide range of resistance phenotypes, although individuals that were either susceptible to all but one pathotype or resistant to all pathotypes were commonest. A strong relationship existed between the cumulative level of disease incurred by B. pubescens individuals in the field and the mean susceptibility of each host line as determined by their reaction to infection by each of the 33 different isolates of M. betulinum individually. Resistance in this B. pubescens population to M. betulinum is postulated to be based on a mixture of quantitative and qualitative traits, selection for which has resulted from an interplay of life history attributes of both host and pathogen.

  • 16.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten.
    The influence of voles and lemmings on the vegetation in a coniferous forest during a 4-year period in northern Sweden1977Doktorsavhandling, monografi (Övrigt vetenskapligt)
  • 17.
    Ericson, Lars
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Burdon, J J
    Muller, W J
    Spatial and temporal dynamics of epidemics of the rust fungus Uromyces valerianae on populations of its host Valeriana salina1999Ingår i: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 87, nr 4, s. 649-658Artikel i tidskrift (Refereegranskat)
  • 18.
    Ericson, Lars
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Burdon, J J
    Muller, W J
    The rust pathogen Triphragmium ulmariae as a selective force affecting its host, Filipendula ulmaria2002Ingår i: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 90, nr 1, s. 167-178Artikel i tidskrift (Refereegranskat)
  • 19.
    Ericson, Lars
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Mueller, Warren J.
    Burdon, Jeremy J.
    28-year temporal sequence of epidemic dynamics in a natural rust-host plant metapopulation2017Ingår i: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 105, nr 3, s. 701-713Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1. A long-term study of disease dynamics caused by the rust Uromyces valerianae in 31 discrete populations of Valeriana salina provides a rare opportunity to explore extended temporal patterns in the epidemiology of a natural host-pathogen metapopulation. 2. Over a 28-year period, pathogen population dynamics varied across the metapopulation with disease incidence (presence/absence), prevalence (% plants infected) and severity (% leaf area covered by lesions) all showing strong population and year effects, indicative of heterogeneity among years and host populations in the suitability of conditions for the pathogen. 3. Disease incidence within individual host populations was significantly affected by host population size, disease prevalence the previous year and the proximity of neighbouring populations infected in the current year. After accounting for these variables there was still a marked temporal component with winter sea level having a significant effect; as did summer rainfall in the second part of the study period (1997-2011). 4. Disease prevalence was also effected by host population size and disease prevalence in the previous year. However, it was less affected by spatial aspects of disease spread than was disease incidence. Winter sea level and June rainfall significantly affected disease prevalence. 5. Assessment of disease impact on plant performance found strong variation in disease severity associated with the aspect and positioning of host populations. Plants growing in lower disease environments produced significantly more seeds than those growing in high disease sites. 6. Significant variation in reaction to infection by U. valerianae was detected among plants within four populations and between these different populations. 7. Synthesis. The epidemiology of Uromyces valerianae was highly influenced by host population size, previous disease and distance. After accounting for these factors, there was a clear temporal signal of change in disease incidence linked to winter sea level and summer rainfall. These patterns reinforce the importance of considering interactions in multiple populations over long periods of time in order to obtain a clear picture of the variability in disease-induced selection pressures across time and space. The behaviour of the pathogen fitted that predicted for a metapopulation with considerable asynchrony in epidemiological patterns among demes.

  • 20.
    Ericson, Lars
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Wennstrom, A
    The effect of herbivory on the interaction between the clonal plant Trientalis europaea and its smut fungus Urocystis trientalis1997Ingår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 80, nr 1, s. 107-111Artikel i tidskrift (Refereegranskat)
  • 21. Fors, Lisa
    et al.
    Markus, Robert
    Theopold, Ulrich
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Hambäck, Peter A.
    Geographic variation and trade-offs in parasitoid virulence2016Ingår i: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 85, nr 6, s. 1595-1604Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1. Host-parasitoid systems are characterized by a continuous development of new defence strategies in hosts and counter-defence mechanisms in parasitoids. This co-evolutionary arms race makes host-parasitoid systems excellent for understanding trade-offs in host use caused by evolutionary changes in host immune responses and parasitoid virulence. However, knowledge obtained from natural host-parasitoid systems on such trade-offs is still limited.

    2. In this study, the aim was to examine trade-offs in parasitoid virulence in Asecodes parviclava (Hymenoptera: Eulophidae) when attacking three closely related beetles: Galerucella pusilla, Galerucella calmariensis and Galerucella tenella (Coleoptera: Chrysomelidae). A second aim was to examine whether geographic variation in parasitoid infectivity or host immune response could explain differences in parasitism rate between northern and southern sites.

    3. More specifically, we wanted to examine whether the capacity to infect host larvae differed depending on the previous host species of the parasitoids and if such differences were connected to differences in the induction of host immune systems. This was achieved by combining controlled parasitism experiments with cytological studies of infected larvae.

    4. Our results reveal that parasitism success in A. parviclava differs both depending on previous and current host species, with a higher virulence when attacking larvae of the same species as the previous host. Virulence was in general high for parasitoids from G. pusilla and low for parasitoids from G. calmariensis. At the same time, G. pusilla larvae had the strongest immune response and G. calmariensis the weakest. These observations were linked to changes in the larval hemocyte composition, showing changes in cell types important for the encapsulation process in individuals infected by more or less virulent parasitoids.

    5. These findings suggest ongoing evolution in parasitoid virulence and host immune response, making the system a strong candidate for further studies on host race formation and speciation.

  • 22.
    Hamback, Peter A.
    et al.
    Department of Ecology, Environment and Plant Sciences, Stockholm University.
    Weingartner, Elisabet
    Department of Ecology, Environment and Plant Sciences, Stockholm University.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Fors, Lisa
    Department of Ecology, Environment and Plant Sciences, Stockholm University.
    Cassel-Lundhagen, Anna
    Swedish University of Agricultural Sciences, Department of Ecology, Uppsala.
    Stenberg, Johan A.
    Swedish University of Agricultural Sciences, Department of Ecology, Uppsala.
    Bergsten, Johannes
    Department of Entomology, Swedish Museum of Natural History, Stockholm.
    Bayesian species delimitation reveals generalist and specialist parasitic wasps on Galerucella beetles (Chrysomelidae): sorting by herbivore or plant host2013Ingår i: BMC Evolutionary Biology, ISSN 1471-2148, E-ISSN 1471-2148, Vol. 13, s. 92-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background:

    To understand the ecological and evolutionary consequences of species interactions in food webs necessitates that interactions are properly identified. Genetic analyses suggest that many supposedly generalist parasitoid species should rather be defined as multiple species with a more narrow diet, reducing the probability that such species may mediate indirect interactions such as apparent competition among hosts. Recent studies showed that the parasitoid Asecodes lucens mediate apparent competition between two hosts, Galerucella tenella and G. calmariensis, affecting both interaction strengths and evolutionary feedbacks. The same parasitoid was also recorded from other species in the genus Galerucella, suggesting that similar indirect effects may also occur for other species pairs.

    Methods:

    To explore the possibility of such interactions, we sequenced mitochondrial and nuclear genetic markers to resolve the phylogeny of both host and parasitoid and to test the number of parasitoid species involved. We thus collected 139 Galerucella larvae from 8 host plant species and sequenced 31 adult beetle and 108 parasitoid individuals.

    Results:

    The analysis of the Galerucella data, that also included sequences from previous studies, verified the five species previously documented as reciprocally monophyletic, but the Bayesian species delimitation for A. lucens suggested 3-4 cryptic taxa with a more specialised host use than previously suggested. The gene data analyzed under the multispecies coalescent model allowed us to reconstruct the species tree phylogeny for both host and parasitoid and we found a fully congruent coevolutionary pattern suggesting that parasitoid speciation followed upon host speciation.

    Conclusion:

    Using multilocus sequence data in a Bayesian species delimitation analysis we propose that hymenopteran parasitoids of the genus Asecodes that infest Galerucella larvae constitute at least three species with narrow diet breath. The evolution of parasitoid Asecodes and host Galerucella show a fully congruent coevolutionary pattern. This finding strengthens the hypothesis that the parasitoid in host search uses cues of the host rather than more general cues of both host and plant.

  • 23. Hambäck, P. A.
    et al.
    Pettersson, J.
    Ericson, L
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Are associational refuges species-specific?2003Ingår i: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, nr 1, s. 87-93Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1. Associational refuges – reduced herbivory on plants in presence of other plant species – may be caused by general and species-specific plant characteristics. However, the species specificity of associational refuges has rarely been evaluated.

    2. This study examined the species specificity of one known example of associational refuges, the forb Lythrum salicaria and the monophagous insect herbivores Galerucella calmariensis, G. pusilla and Nanophyes marmoratus. The underlying mechanism was examined in order to evaluate connections between mechanisms and species specificity.

    3. Laboratory studies showed that N. marmoratus but not Galerucella individuals were attracted by odour from undamaged host plants, and that neither species was distracted by odour from Myrica gale.

    4. Field experiments showed that three non-host plant neighbours with an appearance similar to M. gale, and artificial shrubs, reduced the abundance and egg-laying of Galerucella species by 70–90%. The abundance of N. marmoratus was increased 18-fold on plants in thickets compared with outside.

    5. The different responses by N. marmoratus and the Galerucella species to plant neighbours app

  • 24. Hambäck, PA
    et al.
    Agren, J
    Ericson, L
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Associational resistance: Insect damage to purple loosestrife reduced in thickets of sweet gale2000Ingår i: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 81, nr 7, s. 1784-1794Artikel i tidskrift (Refereegranskat)
  • 25.
    Hambäck, Peter A
    et al.
    Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden.
    Stenberg, Johan A
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Asymmetric indirect interactions mediated by a shared parasitoid: connecting species traits and local distribution patterns for two chrysomelid beetles2006Ingår i: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 148, nr 3, s. 475-481Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper reports on an asymmetric indirect interaction between two chrysomelid beetles where one species (Galerucella tenella) experiences higher parasitization, and the other species (Galerucella calmariensis) lower parasitization, in mixed compared with monospecific populations. This pattern is likely to be a consequence of differences in life history characteristics, where the inferior species has a smaller body size, a lower fecundity and supports a lower parasitoid density than the superior species. This connection between life history characteristics and interspecific dominance in host–parasitoid systems corresponds to predictions from current community ecology theory, and provides a useful building-block in the development of a predictive theory of parasitoid effects on host coexistence.

  • 26. Hedenas, H
    et al.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Epiphytic macrolichens as conservation indicators: successional sequence in Populus tremula stands2000Ingår i: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 93, nr 1, s. 43-53Artikel i tidskrift (Refereegranskat)
  • 27.
    Hedenås, H
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Ericson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Aspen lichens in agricultural and forest landscapes: the importance of habitat quality2004Ingår i: Ecography, Vol. 27, s. 1-11Artikel i tidskrift (Refereegranskat)
  • 28.
    Hedenås, Henrik
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Blomberg, Patrik
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Significance of old aspen (Populus tremula) trees for the occurrence of lichen photobionts2007Ingår i: Biological Conservation, Vol. 135, nr 3, s. 380-387Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the boreal forest landscape, aspen has been effectively selected against in favour of conifers. The decrease in aspen is of particular concern, since it has more host-specific species associated with it than any other boreal tree species. Recently, forest management systems have begun to include green-tree retention in order to maintain structural diversity. Earlier studies have focused on the importance of remnant aspen trees for lichen species prevalence. We have focused on the occurrence of free-living photobionts, i.e. cyanobacteria and green-algae, since a successful establishment of sexually dispersed lichens will depend upon the presence of the photobiont. Our study shows that the abundances of Gloeocystis, Nostoc, Scytonema and Trentepohlia increased with stand age, while the abundance of Trebouxia decreased. The response to clear-felling differed between genera. The two cyanobacterial genera were able to persist in clear-cuts, although they were more abundant on the northern side of the remnant trees. The green-algae showed no consistent pattern, Trentepohlia was affected while Trebouxia was unaffected. Our study indicates that the prerequisites for new-establishment for spore dispersed lichen species, on remnant aspen, may be fulfilled in terms of availability of free-living photobionts on the northern side of the trunks. In support of this interpretation we found that the occurrence of cyanolichens was positively correlated with the occurrence of free-living cyanobacteria in the clear-cuts. We conclude that tree retention is likely to provide a useful tool for increasing biodiversity in managed forest landscapes provided that source populations still exist in the surrounding landscape.

  • 29.
    Hedenås, Henrik
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Species occurrences at stand level cannot be understood without considering the landscape context: Cyanolichens on aspen in boreal Sweden2008Ingår i: Biological Conservation, Vol. 141, s. 710-718Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A major challenge in conservation biology is to understand species’ responses to habitat loss. In Fennoscandia, the ongoing decline in aspen in forests is of particular concern, since aspen is the boreal forest tree species that supports the most host-specific species of cryptogams and invertebrates. In order to predict the potential effects of aspen decline we compared the occurrence of three epiphytic cyanolichens in old-growth stands of the same habitat quality, in four aspen-rich and four aspen-poor landscapes. Collema curtisporum and Collema furfuraceum were, on average, five and six times more frequent, respectively, in the aspen-rich than in the aspen-poor landscapes. Leptogium saturninum was not affected by the abundance of aspen stands at the landscape level. Our data suggests that lichen species with poor dispersal abilities may be more sensitive to habitat loss than more easily dispersed species and that species with broader habitat amplitude may be less sensitive to habitat loss than more specialized species, even if they have inferior dispersal ability. We conclude that (i) predictions of species occurrences at the stand level have to take account of the amount of suitable habitat at the landscape level, and (ii) predicting the responses of individual species based on life-history traits can be crucial, but cannot be based on single traits. Thus our study shows that biological value cannot be assessed on the basis of habitat quality alone and that a landscape perspective is needed for the sustainable management of specialist species.

  • 30.
    Hedenås, Henrik
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Lundin, K
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Interaction between a lichen and a fungal parasite in a successional community: Implications for conservation.2006Ingår i: Journal of Vegetation Science, Vol. 17, s. 207-216Artikel i tidskrift (Refereegranskat)
  • 31. Hjalten , J.
    et al.
    Lindau , A.
    Wennstrom , Anders
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Blomberg , Patrik
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Witzell , J.
    Ericson , Lars
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Vole response to unintentional changes in the chemistry of GM poplars (Chemoecology (2008) 14, (227-232) DOI 10.007/s00049-008-0409-0)2008Ingår i: Chemoecology, ISSN 0937-7409, E-ISSN 1423-0445, Vol. 18, nr 4, s. 263-Artikel i tidskrift (Refereegranskat)
  • 32. Hjalten, J
    et al.
    Danell, K
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Food selection by two vole species in relation to plant growth strategies and plant chemistry1996Ingår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 76, nr 1, s. 181-190Artikel i tidskrift (Refereegranskat)
  • 33. Hjalten, J
    et al.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Roininen, H
    Resistance of Salix caprea, S-phylicifolia, and their F1 hybrids to herbivores and pathogens2000Ingår i: Ecoscience, ISSN 1195-6860, Vol. 7, nr 1, s. 51-56Artikel i tidskrift (Refereegranskat)
  • 34. Hjälten, J.
    et al.
    Lindau, A.
    Wennström, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Blomberg, Patrik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Witzell, J.
    Hurry, V.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Moritz, T.
    Karlsson, Jan
    Vole response to unintentional changes in the chemistry of GM poplars2008Ingår i: Chemoecology, Vol. 180, nr 4, s. 227-231Artikel i tidskrift (Refereegranskat)
    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.

  • 35. Hjälten, J
    et al.
    Niemi, Lena
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Wennström, Anders
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Roininen, H
    Julkunen-Tiitto, R
    Variable responses of natural enemies to Salix triandra phenotypes with different secondary chemistry2007Ingår i: Oikos, Vol. 116, s. 751-758Artikel i tidskrift (Refereegranskat)
  • 36.
    Hjältén, J
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Danell, K
    Ericson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Hare and vole browsing preferences during winter2004Ingår i: Acta Theriologica, Vol. 49, s. 53-62Artikel i tidskrift (Refereegranskat)
  • 37. Hjältén, Joakim
    et al.
    Lindau, Anna
    Wennström, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Blomberg, Patrik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Witzell, Johanna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Hurry, Vaughan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Unintentional changes of defence traits in GM trees can influence plant-herbivore interactions2007Ingår i: Basic and Applied Ecology, Vol. 8, nr 3, s. 434-443Artikel i tidskrift (Refereegranskat)
    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.

  • 38.
    Ingvarsson, P K
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Exploitative competition between two seed parasites on the common sedge, Carex nigra2000Ingår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 91, nr 2, s. 362-370Artikel i tidskrift (Refereegranskat)
  • 39.
    Ingvarsson, P K
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Spatial and temporal variation in disease levels of a floral smut (Anthracoidea heterospora) on Carex nigra1998Ingår i: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 86, nr 1, s. 53-61Artikel i tidskrift (Refereegranskat)
  • 40.
    Ingvarsson, P K
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Olsson, K
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Extinction-recolonization dynamics in the mycophagous beetle Phalacrus substriatus1997Ingår i: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 51, nr 1, s. 187-195Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The population structure of the mycophagous beetle Phalacrus substriatus is characterized by many small, local populations interconnected by migration over a small spatial scale (10 X 75 m(2)). Each local P. substriatus population has a relatively short expected persistence time, but persistence of the species occurs due to a balance between frequent local extinctions and recolonizations. This nonequilibrium population structure can have profound effects on how the genetic variation is structured between and within populations. Theoretical models have stated that the genetic differentiation among local populations will be enhanced relative to an island model at equilibrium if the number of colonizers is less than approximately twice the number of migrants among local populations. To study these effects, a set of 50 local P. substriatus populations were surveyed over a four-year period to record any naturally occurring extinctions and recolonizations. The per population colonization and extinction rate were 0.237 and 0.275, respectively. Mark-recapture techniques were used to estimate a number of demographic parameters: local population size (N = 11.1), migration rate ((m) over cap = 0.366), number of colonizers (k = 4.0), and the probability of common origin of colonizers (phi = 0.5). The theoretically predicted level of differentiation among local populations (measured as Wright's F-ST) was 0.070. Genetic data obtained from an electrophoretic survey of seven polymorphic loci gave an estimated degree of differentiation of 0.077. There was thus a good agreement between the empirical results and the theoretical predictions. Young populations (<(theta)over cap>(young) = 0.090) had significantly higher levels of differentiation than old, more established populations (<(theta)over cap>(old) = 0.059). The extinction-recolonization dynamics resulted in an overall increase in the genetic differentiation among local populations by c. 40%. The global effective population size was also reduced by c. 55%. The results give clear evidence to how nonequilibrium processes shape the genetic structure of populations.

  • 41.
    Johansson, Therese
    et al.
    Department of Animal Ecology, SLU, S-901 83 Umeå, Sweden.
    Olsson, Jörgen
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Hjältén, Joakim
    Department of Animal Ecology, SLU, S-901 83 Umeå, Sweden.
    Jonsson, Bengt Gunnar
    Department of Natural Sciences, Mid Sweden University, S-851 70 Sundsvall, Sweden.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Beetle attraction to sporocarps and wood infected with mycelia of decay fungi in old-growth spruce forest of northern Sweden2006Ingår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 237, nr 1-3, s. 335-341Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many saproxylic beetles do not feed on wood directly but on fungi colonizing the wood. The volume of decaying wood has decreased drastically in Scandinavian managed forest landscapes in recent years, so improved knowledge on the interactions between beetles and wood-decaying fungi is important for the long-term persistence of these trophic partners. Sporocarps of polypores are known to emit volatiles attracting both fungivorous and predatory beetles, but it is unknown whether some beetles are also attracted to odours from the mycelia. The aim of this experiment was to test the attraction of beetles to volatiles from the sporocarps and mycelia of wood-decaying fungi. In a randomized block design, six substrate types: Fomitopsis pinicola sporocarp, F. pinicola mycelium-infected wood, Fomitopsis rosea sporocarp, F. rosea mycelium-infected wood, Phellinus chrysoloma sporocarp and Phlebia centrifuga mycelium-infected wood were attached separately to specially designed window traps in four old-growth spruce forests in northern Sweden. Empty traps and traps with sterilised wood were used as controls. We found no significant differences in the species richness or abundance of saproxylic beetles between the control and sterilised wood and the fungal substrates. However, two abundant species showed significant preferences for one substrate type. The bark beetle Dryocoetes autographus preferred F. rosea mycelium-infected wood and the rove beetle Lordithon lunulatus preferred fruiting bodies of F. pinicola. The results indicate that some species do discriminate between volatiles emitted by different polypore species and also between volatiles emitted by the sporocarps and mycelia from the same species. Our data indicate a hitherto unknown interdependence between D. autographus and F. rosea. We conclude that present knowledge on interactions between beetles and wood-decaying fungi is limited and further studies are needed to enhance our ability to design appropriate conservation strategies in the forest landscape.

  • 42. Kruys, Åsa
    et al.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Species richness of coprophilous ascomycetes in relation to variable food intake by herbivores2008Ingår i: Fungal Diversity, Vol. 30, s. 73-81Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this study was to study species richness and species composition of coprophilous ascomycetes in borcal forest. Dung was sampled at three localities and of three herbivores; moose (Alces alces), mountain hare (Lepus timidus), and roe deer (Capreolus capreolus). Species richness differed significantly among dung types and we also found a significant effect of the interaction between locality and dung type on the mean number of species. The highest species richness was found on roe deer dung. While moose did not differ from mountain hare. There was a strong positive relationship between the total number of ascomycete species and the number of plant species foraged by the three herbivores. We believe that food choice is one important factor influencing the species richness of coprophilous ascomycetes, and that some species are more associated with habitat and food choice of the herbivore, rather than a specific dung type/animal species. The composition of species on the different dung types is also discussed. Our results suggests that the coprophilous mycota in the boreal forest is poorly known; we found 47 species in total, four species were undescribed. I was new to Sweden, 24 species were new records for the province, and we made a total of 22 new substrate records.

  • 43. Lehndal, Lina
    et al.
    Hambäck, Peter A
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ågren, Jon
    Herbivory strongly influences among-population variation in reproductive output of Lythrum salicaria in its native range2016Ingår i: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 180, nr 4, s. 1159-1171Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Herbivory can negatively affect several components of plant reproduction. Yet, because of a lack of experimental studies involving multiple populations, the extent to which differences in herbivory contribute to among-population variation in plant reproductive success is poorly known. We experimentally determined the effects of insect herbivory on reproductive output in nine natural populations of the perennial herb Lythrum salicaria along a disturbance gradient in an archipelago in northern Sweden, and we quantified among-population differentiation in resistance to herbivory in a common-garden experiment in the same area. The intensity of leaf herbivory varied > 500-fold and mean female reproductive success > 400-fold among the study populations. The intensity of herbivory was lowest in populations subject to strong disturbance from ice and wave action. Experimental removal of insect herbivores showed that the effect of herbivory on female reproductive success was correlated with the intensity of herbivory and that differences in insect herbivory could explain much of the among-population variation in the proportion of plants flowering and seed production. Population differentiation in resistance to herbivory was limited. The results demonstrate that the intensity of herbivory is a major determinant of flowering and seed output in L. salicaria, but that differences in herbivory are not associated with differences in plant resistance at the spatial scale examined. They further suggest that the physical disturbance regime may strongly influence the performance and abundance of perennial herbs and patterns of selection not only because of its effect on interspecific competition, but also because of effects on interactions with specialized herbivores.

  • 44. Moen, J
    et al.
    Gardfjell, H
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Oksanen, L
    Shoot survival under intense grazing for two broad-leaved herbs with different chemical defense systems1996Ingår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 75, nr 3, s. 359-364Artikel i tidskrift (Refereegranskat)
  • 45.
    Niemi, Lena
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Wennström, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Insect feeding preferences and plant phenolic glucosides in the system Gonioctena linnaeana-Salix triandra2005Ingår i: Entomologia Experimentalis et Applicata, ISSN 0013-8703, E-ISSN 1570-7458, Vol. 115, nr 1, s. 61-66Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 46. Nordin, A
    et al.
    Nasholm, T
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Effects of simulated N deposition on understorey vegetation of a boreal coniferous forest1998Ingår i: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 12, nr 4, s. 691-699Artikel i tidskrift (Refereegranskat)
  • 47. Nordin, A
    et al.
    Strengbom, J
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Ericson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Responses to ammonium and nitrate additions by boreal plants and their natural enemies2006Ingår i: Environmental Pollution, Vol. 141, nr 1, s. 167-174Artikel i tidskrift (Refereegranskat)
  • 48. Nordin, A
    et al.
    Strengbom, J
    Forsum, Å
    Ericson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Complex biotic interactions drive long-term vegetation change in a nitrogen enriched boreal forest2009Ingår i: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 12, s. 1204-1211Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effects of experimental nitrogen (N) additions (0, 12.5, and 50 kg N ha-1 y-1) on long-term (12 years) understorey vegetation dynamics were examined in a boreal forest. The results showed that two types of natural enemies of the dominant dwarf-shrub Vaccinium myrtillus (pathogenic fungus of the species Valdensia heterodoxa and herbivorous larvae of the genus Operophtera) influenced the vegetation dynamics. The pathogenic fungus, causing premature leaf-shed of V. myrtillus, showed a strong positive N response during the initial 5-year period. For the larvae, a relatively modest N response was overshadowed by an almost 40-fold population increase during an outbreak event that followed the initial 5-year period. This outbreak occurred irrespective of N addition, resulting in V. myrtillus decline and depriving the pathogenic fungus of its substrate. Hence our study demonstrates that vegetation dynamics in this relatively species poor and seemingly simple ecosystem are driven by complex biotic interactions. Further, we show that an important component of these interactions is the temporal alternation of the two natural enemies and, resultant regulation of the dominant plant's abundance. Finally, we emphasize that long-term data are essential to capture the complexity of this type of biotic interactions. In our case, a short-term study may have resulted in markedly different conclusions regarding effects of N enrichment and the role of biotic interactions for forest vegetation dynamics.

  • 49. Nordin, A
    et al.
    Strengbom, J
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Witzell, J
    Näsholm, T
    Ericson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Nitrogen deposition and the biodiversity of boreal forests: Implications for the nitrogen critical load2005Ingår i: Ambio, Vol. 34, s. 20-24Artikel i tidskrift (Refereegranskat)
  • 50. Norstedt, G
    et al.
    Bader, P
    Ericson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Polypores as indicators of conservation value in Corsican pine forests2001Ingår i: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 99, nr 3, s. 347-354Artikel i tidskrift (Refereegranskat)
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