Browsing Institutt for matematiske fag by Author "Engen, Steinar"

Now showing items 1-20 of 21

    • Accounting for interspecific competition and age structure in demographic analyses of density dependence improves predictions of fluctuations in population size 

      Gamelon, Marlène; Vriend, Stefan; Engen, Steinar; Adriaensen, Frank; Dhondt, A.A.; Evans, Simon R.; Matthysen, Erik; Sheldon, Ben C.; Sæther, Bernt-Erik (Peer reviewed; Journal article, 2019)
      Understanding species coexistence has long been a major goal of ecology. Coexistence theory for two competing species posits that intraspecific density dependence should be stronger than interspecific density dependence. ...

    • Age-dependent patterns of spatial autocorrelation in fish populations 

      Marquez, Jonatan; Sæther, Bernt-Erik; Aanes, Sondre; Engen, Steinar; Salthaug, Are; Lee, Aline Magdalena (Journal article; Peer reviewed, 2021)
      The degree of spatial autocorrelation in population fluctuations increases with dispersal and geographical covariation in the environment, and decreases with strength of density dependence. Because the effects of these ...

    • Characteristics of temporal changes in communities where dynamics differ between species 

      Solbu, Erik Blystad; Engen, Steinar; Diserud, Ola Håvard (Journal article; Peer reviewed, 2016)
      Communities with different phenotypic variation among species can have identical species abundance distributions, although their temporal dynamics may be very different. By using stochastic species abundance models, both ...

    • Consequences of barriers and changing seasonality on population dynamics and harvest of migratory ungulates 

      Van Moorter, Bram; Engen, Steinar; Fryxell, John M.; Panzacchi, Manuela; Nilsen, Erlend Birkeland; Mysterud, Atle (Peer reviewed; Journal article, 2020)
      Many animal populations providing ecosystem services, including harvest, live in seasonal environments and migrate between seasonally distinct ranges. Unfortunately, two major sources of human-induced global change threaten ...

    • Contrasting patterns of density-dependent selection at different life stages can create more than one fast–slow axis of life-history variation 

      Wright, Jonathan; Solbu, Erik Blystad; Engen, Steinar (Journal article; Peer reviewed, 2020)
      There has been much recent research interest in the existence of a major axis of life‐history variation along a fast–slow continuum within almost all major taxonomic groups. Eco‐evolutionary models of density‐dependent ...

    • Decomposing demographic contributions to the effective population size with moose as a case study 

      Lee, Aline Magdalena; Myhre, Ane Marlene; Markussen, Stine Svalheim; Engen, Steinar; Solberg, Erling Johan; Haanes, Hallvard; Røed, Knut; Herfindal, Ivar; Heim, Morten; Sæther, Bernt-Erik (Peer reviewed; Journal article, 2020)
      Levels of random genetic drift are influenced by demographic factors, such as mating system, sex ratio and age structure. The effective population size (N e) is a useful measure for quantifying genetic drift. Evaluating ...

    • Decomposing demographic contributions to the effective population size with moose as a case study 

      Lee, Aline Magdalena; Svalheim Markussen, Stine; Engen, Steinar; Solberg, Erling Johan; Haanes, Hallvard; Røed, Knut H.; Herfindal, Ivar; Heim, Morten; Sæther, Bernt-Erik (Journal article; Peer reviewed, 2020)
      Levels of random genetic drift are influenced by demographic factors, such as mating system, sex ratio and age structure. The effective population size (Ne) is a useful measure for quantifying genetic drift. Evaluating ...

    • Demographic routes to variability and regulation in bird populations 

      Sæther, Bernt-Erik; Grøtan, Vidar; Engen, Steinar; Coulson, Tim; Grant, Peter R.; Visser, Marcel E.; Brommer, Jon E.; Grant, B. Rosemary; Gustafsson, Lars; Hatchwell, Ben J.; Jerstad, Kurt; Karell, Patrik; Pietiäinen, Hannu; Roulin, Alexandre; Røstad, Ole Wiggo; Weimerskirch, Henri (Journal article; Peer reviewed, 2016)
      There is large interspecific variation in the magnitude of population fluctuations, even among closely related species. The factors generating this variation are not well understood, primarily because of the challenges ...

    • Ecological dynamics and large scale phenotypic differentiation in density-dependent populations 

      Engen, Steinar; Sæther, Bernt-Erik (Journal article; Peer reviewed, 2019)
      Spatial differentiation of phenotypes is assumed to be determined by a combination of fluctuating selection producing adaptations to the local environment and a homogenizing effect of migration. We present a model with ...

    • The ecological dynamics of the coronavirus epidemics during transmission from outside sources when R0 is successfully managed below one 

      Engen, Steinar; Tian, Huaiyu; Yang, Ruifu; Bjørnstad, Ottar Nordal; Whittington, Jason; Stenseth, Nils Christian (Peer reviewed; Journal article, 2021)
      Since COVID-19 spread globally in early 2020 and was declared a pandemic by the World Health Organization (WHO) in March, many countries are managing the local epidemics effectively through intervention measures that limit ...

    • Harvest-induced phenotypic selection in an island population of moose, Alces alces 

      Kvalnes, Thomas; Sæther, Bernt-Erik; Haanes, Hallvard; Røed, Knut; Engen, Steinar; Solberg, Erling Johan (Journal article; Peer reviewed, 2016)
      Empirical evidence strongly indicates that human exploitation has frequently led to rapid evolutionary changes in wild populations, yet the mechanisms involved are often poorly understood. Here, we applied a recently ...

    • Heterogeneity among species and community dynamics – Norwegian bird communities as a case study 

      Solbu, Erik Blystad; Diserud, Ola Håvard; Kålås, John Atle; Engen, Steinar (Journal article; Peer reviewed, 2018)
      We have in this study analysed bird communities across Norway with a heterogeneous species abundance model, where dynamical parameters can vary among species. Similarity in community composition over time, used as a measure ...

    • Interactions between demography and environmental effects are important determinants of population dynamics 

      Gamelon, Marlène; Grøtan, Vidar; Nilsson, Anna L. K.; Engen, Steinar; Hurrell, James W.; Jerstad, Kurt; Phillips, Adam S.; Røstad, Ole Wiggo; Slagsvold, Tore; Walseng, Bjørn; Stenseth, Nils Christian; Sæther, Bernt-Erik (Journal article; Peer reviewed, 2017)
      Climate change will affect the population dynamics of many species, yet the consequences for the long-term persistence of populations are poorly understood. A major reason for this is that density-dependent feedback effects ...

    • Interactions between demography and environmental effects are important determinants of population dynamics 

      Gamelon, Marlène; Grøtan, Vidar; Nilsson, Anna; Engen, Steinar; Hurrell, James W.; Jerstad, Kurt; Phillips, Adam S.; Røstad, Ole Wiggo; Slagsvold, Tore; Walseng, Bjørn; Stenseth, Nils Christian; Sæther, Bernt-Erik (Journal article; Peer reviewed, 2017)
      Climate change will affect the population dynamics of many species, yet the consequences for the long-term persistence of populations are poorly understood. A major reason for this is that density-dependent feedback effects ...

    • Modelling time to population extinction when individual reproduction is autocorrelated 

      Lee, Aline Magdalena; Sæther, Bernt-Erik; Markussen, Stine Svalheim; Engen, Steinar (Peer reviewed; Journal article, 2017)
      In nature, individual reproductive success is seldom independent from year to year, due to factors such as reproductive costs and individual heterogeneity. However, population projection models that incorporate temporal ...

    • Seasonal diversity dynamics of a boreal zooplankton community under climate impact 

      Bellier, Edwige; Engen, Steinar; Jensen, Thomas Correll (Journal article; Peer reviewed, 2022)
      Seasonality and long-term environmental variability afect species diversity through their efects on the dynamics of species. To investigate such efects, we ftted a dynamic and heterogeneous species abundance model generating ...

    • Spatial scales of population synchrony in predator-prey systems 

      Jarillo, Javier Diaz; Sæther, Bernt-Erik; Engen, Steinar; Cao-Garcia, Francisco (Peer reviewed; Journal article, 2020)
      Many species show synchronous fluctuations in population size over large geographical areas, which are likely to increase their regional extinction risk. Here we examine how the degree of spatial synchrony in population ...

    • Spatial scaling of population synchrony in marine fish depends on their life history 

      Fredricson Marquez, Jonatan; Lee, Aline Magdalena; Aanes, Sondre; Engen, Steinar; Herfindal, Ivar; Salthaug, Are; Sæther, Bernt-Erik (Peer reviewed; Journal article, 2019)
      The synchrony of population dynamics in space has important implications for ecological processes, for example affecting the spread of diseases, spatial distributions and risk of extinction. Here, we studied the relationship ...

    • Sustainable strategies for harvesting predators and prey in a fluctuating environment 

      Bellier, Edwige; Sæther, Bernt-Erik; Engen, Steinar (Peer reviewed; Journal article, 2021)
      The effects of harvest and fluctuating environment on inter-dependent predators and prey are complex and not well-known. We define a stochastic model where the predators and prey dynamically interact. The novelty of the ...

    • Temporal changes in parameters describing stochastic population dynamics 

      Solbu, Erik Blystad (Master thesis, 2011)
      The solution of a stochastic differential equation with temporally dependent parameters is the basis for the following analysis of stochastic population dynamics with temporal changes in the parameters. A discrete density ...