Blar i NTNU Open på forfatter "Engen, Steinar"
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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 ... -
An integrated population model for a long-lived ungulate: more efficient data use with Bayesian methods
Lee, Aline Magdalena; Bjørkvoll, Eirin Marie; Hansen, Brage Bremset; Albon, Steve D.; Stien, Audun; Sæther, Bernt-Erik; Engen, Steinar; Veiberg, Vebjørn; Loe, Leif Egil; Grøtan, Vidar (Journal article, 2015)We develop an integrated population model for Svalbard reindeer Rangifer tarandus platyrhynchus, and demonstrate how this type of model can be used to extract more information from the data and separate different sources ... -
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 buffering of life histories? Implications of the choice of measurement scale
Bjørkvoll, Eirin Marie; Lee, Aline Magdalena; Grøtan, Vidar; Sæther, Bernt-Erik; Stien, Audun; Engen, Steinar; Albon, Steve D.; Loe, Leif Egil; Hansen, Brage Bremset (Journal article; Peer reviewed, 2016)Life-history theory predicts that the vital rates that influence population growth the most should be buffered against environmental fluctuations due to selection for reduced variation. However, it remains unclear whether ... -
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 ... -
Density-dependent selection and the maintenance of colour polymorphism in barn owls
Kvalnes, Thomas; Sæther, Bernt-Erik; Engen, Steinar; Roulin, Alexandre (Peer reviewed; Journal article, 2022)The capacity of natural selection to generate adaptive changes is (according to the fundamental theorem of natural selection) proportional to the additive genetic variance in fitness. In spite of its importance for development ... -
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 ... -
Effective size of density dependent populations in fluctuating environments
Myhre, Ane Marlene (Doctoral theses at NTNU;2017:156, Doctoral thesis, 2017)Knowledge of the effective size of populations, Ne, and the ratio of effective population size to the size of the mature population Ne/N, provide important information of the genetic diversity and fitness of populations. ... -
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 ... -
Harvesting can stabilise population fluctuations and buffer the impacts of extreme climatic events
Peeters, Bart; Grøtan, Vidar; Gamelon, Marlène; Veiberg, Vebjørn; Lee, Aline Magdalena; Fryxell, John M.; Albon, Steve D.; Sæther, Bernt-Erik; Engen, Steinar; Loe, Leif Egil; Hansen, Brage Bremset (Peer reviewed; Journal article, 2022)Harvesting can magnify the destabilising effects of environmental perturbations on population dynamics and, thereby, increase extinction risk. However, population-dynamic theory predicts that impacts of harvesting depend ... -
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 ...