Now showing items 41-60 of 86

    • Integrating dispersal along freshwater ecosystems into species distribution models 

      Perrin, Sam Wenaas; Englund, Göran; Blumentrath, Stefan; O'Hara, Robert Brian; Amundsen, Per-Arne; Finstad, Anders Gravbrøt (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-29)
      <i>Aim</i> - Our ability to model species distributions and abundances is a valuable ecological tool in predicting future distributions of species. Effectively incorporating connectivity into these predictions is crucial; however, many connectivity measures utilize metrics which may not have a direct relation to the dispersal capacity of the species they are attempting to model. The identification ...
    • Invader population speeds up life history during colonization 

      Amundsen, Per-Arne; Salonen, Erno; Niva, Teuvo; Gjelland, Karl Øystein; Præbel, Kim; Sandlund, Odd Terje; Knudsen, Rune; Bøhn, Thomas (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)
      We explore the long-term developments in population biology and life history during the invasion and establishment of the fish species vendace Coregonus albula in a subarctic watercourse by comparing life-history traits and molecular genetic estimates between the source and the colonist population. The two populations exhibited highly contrasting life-history strategies. Relative to the source ...
    • Invasion genetics of vendace (Coregonus albula (L.)) in the Inari-Pasvik watercourse: revealing the origin and expansion pattern of a rapid colonization event 

      Præbel, Kim; Gjelland, Karl Øystein; Salonen, Erno; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Species invasions can have wide-ranging biological and socio-economic effects and are generally unwanted by legislation. Identification of the source population as well as the ecology and genetics of both the invader population and the receiving community is of crucial importance. The rapid invasion of a small coregonid fish vendace (Coregonus albula) in a major northern European subarctic watercourse ...
    • Invasion-mediated changes in the population biology of a dimorphic whitefish Coregonus lavaretus population 

      Bøhn, Thomas; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2004-02-26)
      Population biology changes in native dimorphic whitefish <i>Coregonus lavaretus</i> were studied over a decade in the subarctic Pasvik watercourse, where large biotric changes occurred due to an invasion by vendace <i> C. albula</i>. Although initially recorded in the upstream part of the watercourse, where it is now the dominant pelagic species, the vendace subsequently also colonised the downstream ...
    • Is coexistence mediated by microhabitat segregation? An in-depth exploration of a fish invasion 

      Gjelland, Karl Øystein; Bøhn, Thomas; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)
      Vendace <i>Coregonus albula</i> has invaded the subarctic Pasvik hydrosystem, northern Norway and Russia, after being translocated from its native Finnish range into Lake Inari (Finland), upstream of Pasvik. The development of the invader and the effects on two native lake communities in the upstream and downstream part of the hydrosystem, respectively, have been monitored since 1991. In the upstream ...
    • Lagesilda i Pasvikvassdraget : langtidseffekter av en biologisk invasjon 

      Amundsen, Per-Arne; Gjelland, Karl Øystein; Knudsen, Rune; DalsbØ, laina h; Lien, Cesilie; Evjen, jan knut (Research report; Forskningsrapport, 2012)
      Pasvikvassdraget har siden 1991 vært gjenstand for omfattende økologiske studier i regi av Ferskvannsøkologisk faggruppe ved Universitetet i Tromsø. Undersøkelsene har særlig vært rettet mot å undersøke effektene av at lagesilda, en fremmed fiskeart for Nord-Norge, kom inn i vassdraget på slutten av 1980-tallet. For å få en grundig forståelse av økologien i vassdraget har studiene også omfattet ...
    • Lake size and fish diversity determine resource use and trophic position of a top predator in high-latitude lakes 

      Eloranta, Antti; Kahilainen, Kimmo K.; Amundsen, Per-Arne; Knudsen, Rune; Harrod, Chris; Jones, Roger I. (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-03-23)
      Prey preference of top predators and energy flow across habitat boundaries are of fundamental importance for structure and function of aquatic and terrestrial ecosystems, as they may have strong effects on production, species diversity, and food-web stability. In lakes, littoral and pelagic food-web compartments are typically coupled and controlled by generalist fish top predators. However, the ...
    • Long-term ecological studies in northern lakes – challenges, experiences, and accomplishments 

      Amundsen, Per-Arne; Primicerio, Raul; Smalås, Aslak; Henriksen, Eirik Haugstvedt; Knudsen, Rune; Kristoffersen, Roar; Klemetsen, Anders (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-15)
      We review three long‐term research programs performed over the last four decades on the ecology and management of oligotrophic lake systems with different fish communities at 69&deg; N in Norway. Through whole‐lake perturbation experiments, intensive culling of stunted fish removed 35 tons (1984–1991) of Arctic charr <i>Salvelinus alpinus</i> in Takvatn (15 km<sup>2</sup>) and 153 tons (1981–1983, ...
    • Long-term responses of zooplankton to invasion by a planktivorous fish in a subarctic watercourse 

      Amundsen, Per-Arne; Siwertsson, Anna; Primicerio, Raul; Bøhn, Thomas (Journal article; Tidsskriftartikkel; Peer reviewed, 2008-08-13)
      <p>1. Introduced or invading predators may have strong impacts on prey populations of the recipient community mediated by direct and indirect interactions. The long‐term progression of predation effects, covering the invasion and establishment phase of alien predators, however, has rarely been documented.</p> <p>2. This paper documents the impact of an invasive, specialized planktivorous fish ...
    • Molecular analyses reveal high cryptic diversity of trematodes in a sub-Arctic lake 

      Soldánová, Miroslava; Georgieva, Simona; Roháčová, Jana; Knudsen, Rune; Kuhn, Jesper A.; Henriksen, Eirik Haugstvedt; Siwertsson, Anna; Shaw, Jenny C.; Kuris, Armand M.; Amundsen, Per-Arne; Scholz, Tomas; Lafferty, Kevin D.; Kostadinova, Aneta (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03-14)
      To identify trematode diversity and life-cycles in the sub-Arctic Lake Takvatn, Norway, we characterised 120 trematode isolates from mollusc first intermediate hosts, metacercariae from second intermediate host fishes and invertebrates, and adults from fish and invertebrate definitive hosts, using molecular techniques. Phylogenies based on nuclear and/or mtDNA revealed high species richness (24 ...
    • Morphological divergence between three Arctic charr morphs - the significance of the deep-water environment. 

      Skoglund, Sigrid Østrem; Siwertsson, Anna; Knudsen, Rune; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-07-14)
      Morphological divergence was evident among three sympatric morphs of Arctic charr (Salvelinus alpinus (L.)) that are ecologically diverged along the shallow-, deep-water resource axis in a subarctic postglacial lake (Norway). The two deep-water (profundal) spawning morphs, a benthivore (PB-morph) and a piscivore (PP-morph), have evolved under identical abiotic conditions with constant low light ...
    • New parasites and predators follow the introduction of two fish species to a subarctic lake: implications for food-web structure and functioning 

      Amundsen, Per-Arne; Lafferty, Kevin D.; Knudsen, Rune; Primicerio, Raul; Kristoffersen, Roar; Klemetsen, Anders; Kuris, Armand M (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)
      Introduced species can alter the topology of food webs. For instance, an introduction can aid the arrival of free-living consumers using the new species as a resource, while new parasites may also arrive with the introduced species. Food-web responses to species additions can thus be far more complex than anticipated. In a subarctic pelagic food web with free-living and parasitic species, two fish ...
    • Ontogenetic dynamics of infection with Diphyllobothrium spp. cestodes in sympatric Arctic charr Salvelinus alpinus (L.) and brown trout Salmo trutta L. 

      Henriksen, Eirik Haugstvedt; Knudsen, Rune; Kristoffersen, Roar; Kuris, Armand M.; Lafferty, Kevin D.; Siwertsson, Anna; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-12-23)
      The trophic niches of Arctic charr and brown trout differ when the species occur in sympatry . Their trophically transmitted parasit es are expected to reflect these differences. Here , we investigate how the infections of Diphyllobothrium dendriticum and Diphyllobothrium ditremum differ between charr and trout. These tapeworms use copepods ...
    • Ontogenetic niche shifts and resource partitioning in a subarctic piscivorous fish guild 

      Amundsen, Per-Arne; Bøhn, Thomas; Popova, Olga A.; Staldvik, Frode J.; Reshetnikov, Yuri S.; Kashulin, Nikolay A.; Lukin, Anatoly A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2003-05)
      The feeding ecology of three piscivorous fish species (perch (<i>Perca fluviatilis</i>), pike (<i>Esox lucius</i>) and burbot (<i>Lota lota</i>)), was studied in the subarctic Pasvik watercourse (69 ° N), northern Norway and Russia. All three species primarily occupied the benthic habitats in the watercourse. Perch and burbot exhibited distinct ontogenetic niche shifts in food resource use, perch ...
    • Parallel and non-parallel morphological divergence among foraging specialists in European whitefish (Coregonus lavaretus) 

      Siwertsson, Anna; Knudsen, Rune; Adams, Colin Ean; Præbel, Kim; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Parallel phenotypic evolution occurs when independent populations evolve similar traits in response to similar selective regimes. However, populations inhabiting similar environments also frequently show some phenotypic differences that result from non-parallel evolution. In this study, we quantified the relative importance of parallel evolution to similar foraging regimes and nonparallel lake-specific ...
    • Parasite communities of two three-spined stickleback populations in subarctic Norway—effects of a small spatial-scale host introduction 

      Kuhn, Jesper Andreas; Kristoffersen, Roar; Knudsen, Rune; Jakobsen, Jonas; Marcogliese, D. J.; Locke, S. A.; Primicerio, Raul; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-01-30)
      We compared metazoan parasite communities of an introduced three-spined stickleback (Gasterosteus aculeatus) population with the nearby source population in northern Norway to study differences and clarify if factors controlling parasite dispersal act on a small spatialscale. The two component communities were highly similar. All parasite taxa found in the source population also occurred in the ...
    • Parasites as prey in aquatic food webs: implications for predator infection and parasite transmission 

      Thieltges, David W.; Amundsen, Per-Arne; Hechinger, Ryan F.; Johnson, Pieter T.J.; Lafferty, Kevin D.; Mouritsen, Kim N.; Preston, Daniel L.; Reise, Karsten; Zander, C. Dieter; Poulin, Robert (Journal article; Tidsskriftartikkel; Peer reviewed, 2013-04-25)
      While the recent inclusion of parasites into food-web studies has highlighted the role of parasites as consumers, there is accumulating evidence that parasites can also serve as prey for predators. Here we investigated empirical patterns of predation on parasites and their relationships with parasite transmission in eight topological food webs representing marine and freshwater ecosystems. Within ...
    • Parasitism and the Biodiversity-Functioning Relationship 

      Frainer, André; McKie, Brendan G.; Amundsen, Per-Arne; Knudsen, Rune; Lafferty, Kevin D. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-02-15)
      Species interactions can influence ecosystem functioning by enhancing or suppressing the activities of species that drive ecosystem processes, or by causing changes in biodiversity. However, one important class of species interactions – parasitism – has been little considered in biodiversity and ecosystem functioning (BD-EF) research. Parasites might increase or decrease ecosystem processes by ...
    • Patterns and repeatability of multi-ecotype assemblages of sympatric salmonids 

      Blain, Stephanie A.; Schluter, Dolph; Adams, Colin E.; Amundsen, Per-Arne; Knudsen, Rune; Chavarie, Louise (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-04)
      Aim: High repeatability among assemblages of closely related but ecologically distinct ecotypes implies predictability in evolution and assembly of communities. The conditions under which ecotype assemblages form predictably, and the reasons, have been little investigated. Here, we test whether repeatability declines as the number of ecotypes builds.<p> <p>Location: Postglacial lakes with a ...
    • Phenotype-environment association of the oxygen transport system in trimorphic European whitefish (Coregonus lavaretus) populations 

      Evans, Melissa; Præbel, Kim; Peruzzi, Stefano; Amundsen, Per-Arne; Bernatchez, Louis (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-05-23)