eifossen

• Moreira-Soares, Maurício; Fossen, Erlend I. F.; Bilbao-Jayo, Aritz; Almeida, Aitor; Lopez-Perez, Laura & Alonso, Itziar [Vis alle 16 forfattere av denne artikkelen] (2026). Joint probability framework for the development and validation of a prognostic model for the conditional outcome of quality of life: a retrospective study in historical European cohorts of survivors of head and neck cancer. The Lancet Digital Health. 8(5). doi: 10.1016/j.landig.2025.100976. Fulltekst i vitenarkiv
• Bruijning, Marjolein; Meester, Luc De; Visser, Marco D.; Fossen, Erlend I. F.; Vanvelk, Héléne & Raeymaekers, Joost A. M. [Vis alle 10 forfattere av denne artikkelen] (2025). Linking Individual Performance to Density‐Dependent Population Dynamics to Understand Temperature‐Mediated Genotype Coexistence. Ecology Letters. ISSN 1461-023X. 28, s. 1–13. doi: 10.1111/ele.70214. Fulltekst i vitenarkiv Vis sammendrag

  The persistence of local populations exposed to climate change depends on their adaptive potential and on the ability of local individuals to compete with migrating conspecifics tracking environmental shifts. Modern coexistence theory (MCT) offers a framework for studying such competitive interactions among genotypes. However, MCT often focuses on emerging population‐level outcomes, aggregating over the underlying individual‐level interactions. We present a cross‐scale application of MCT, combining it with an Integral Projection Model (IPM), explicitly connecting individual performance to population‐level dynamics. We parameterise our model using experimental data on competing Daphnia genotypes from two latitudes. Consistent with observations, our model shows that higher temperatures increase the likelihood of competitive exclusion of Northern genotypes by Southern genotypes. Moreover, it reveals latitudinal variation in neonate sex ratios as a driver of temperature‐dependent evolutionary shifts. By identifying vital rates underlying population‐level competitive outcomes, our approach preserves the straightforward theoretical interpretability of MCT, while providing enhanced process‐level resolution through IPMs.

• Sekajova, Zuzana; Fossen, Erlend Ignacio Fleck; Rosa, Elena; Ratikainen, Irja Ida; Tourniaire-blum, Manon & Lind, Martin (2025). Evolution of phenotypic plasticity during environmental fluctuations. Journal of Evolutionary Biology. ISSN 1010-061X. 38, s. 1–10. doi: 10.1093/jeb/voaf078. Fulltekst i vitenarkiv Vis sammendrag

  Evolution in variable environments is predicted to disfavour genetic canalization and instead select for alternative strategies, such as phenotypic plasticity or possibly bet-hedging, depending on the accuracy of environmental cues and type of variation. While these two alternatives are often contrasted in theoretical studies, their evolution are seldom studied together in empirical work. We used experimental evolution for 30 generations in the nematode worm Caenorhabditis remanei to simultaneously study the evolution of plasticity and bet-hedging in environments differing only in their temperature variability, where one regime is exposed to faster temperature cycles between 20 and 25 °C, with little autocorrelation between parent and offspring environment, while the other regime had slowly increasing temperature with high autocorrelation in temperature between parent and offspring. These two environments had the same average temperature over evolutionary time, but one varied with larger magnitude on a shorter time scale. After experimental evolution, we scored adult size and fitness in full siblings reared in two different temperatures, optimal 20 °C and mildly stressful 25 °C. Experimental evolution in fast temperature cycles resulted in the evolution of increased body size plasticity but not increased bet-hedging, compared to evolution in the slowly changing environment. Plasticity followed the temperature–size rule as size decreased with increasing temperature and this plastic response was adaptive. In addition, we documented substantial standing genetic variation in body size, which represents a potential for further evolutionary change.

• Moreira-Soares, Maurício; Fossen, Erlend Ignacio Fleck; Taylor, Katherine; Singer, Susanne; Hurley, Katrina & Thomas, Steve [Vis alle 16 forfattere av denne artikkelen] (2024). Quality of life in head and neck cancer survivors: the Big Data for Quality of Life study. medRxiv. doi: 10.1101/2024.02.02.24302118. Fulltekst i vitenarkiv
• Fossen, Erlend Ignacio Fleck; Moreira-Soares, Maurício; Leblanc, Marissa Erin; Frigessi, Arnoldo; Hovig, Eivind & Lopez-Perez, Laura [Vis alle 20 forfattere av denne artikkelen] (2024). External validation of prognostic and predictive gene signatures in head and neck cancer patients. medRxiv. doi: 10.1101/2024.09.24.24314278. Fulltekst i vitenarkiv
• Moreira-Soares, Maurício; Fossen, Erlend Ignacio Fleck; Bilbao-Jayo, Aritz; Almeida, Aitor; Lopez-Perez, Laura & Alonso, Itziar [Vis alle 17 forfattere av denne artikkelen] (2024). Joint probability approach for prognostic prediction of conditional outcomes: application to quality of life in head and neck cancer survivors. medRxiv. Fulltekst i vitenarkiv
• Sekajova, Zuzana; Fossen, Erlend Ignacio Fleck; Rosa, Elena; Ratikainen, Irja Ida; Tourniaire-blum, Manon & Bolund, Elisabeth [Vis alle 7 forfattere av denne artikkelen] (2023). Evolution during uncorrelated environmental fluctuations: bet-hedging or phenotypic plasticity? BioRxiv. ISSN 0362-4331. doi: 10.1101/2023.01.22.523389. Fulltekst i vitenarkiv
• Einum, Sigurd; Bartuseviciute, Vitalija; Fossen, Erlend Ignacio Fleck & Pelabon, Christophe (2022). Inferring temperature adaptation from thermal performance curves of somatic growth rate: The importance of growth measurements and mortality. Journal of Evolutionary Biology. ISSN 1010-061X. 36(2). doi: 10.1111/jeb.14136. Fulltekst i vitenarkiv Vis sammendrag

  When comparing somatic growth thermal performance curves (TPCs), higher somatic growth across experimental temperatures is often observed for populations originating from colder environments. Such countergradient variation has been suggested to represent adaptation to seasonality, or shorter favourable seasons in colder climates. Alternatively, populations from cold climates may outgrow those from warmer climates at low temperature, and vice versa at high temperature, representing adaptation to temperature. Using modelling, we show that distinguishing between these two types of adaptation based on TPCs requires knowledge about (i) the relationship between somatic growth rate and population growth rate, which in turn depends on the scale of somatic growth (absolute or proportional), and (ii) the relationship between somatic growth rate and mortality rate in the wild. We illustrate this by quantifying somatic growth rate TPCs for three populations of Daphnia magna where population growth scales linearly with proportional somatic growth. For absolute somatic growth, the northern population outperformed the two more southern populations across temperatures, and more so at higher temperatures, consistent with adaptation to seasonality. In contrast, for the proportional somatic growth TPCs, and hence population growth rate, TPCs tended to converge towards the highest temperatures. Thus, if the northern population pays an ecological mortality cost of rapid growth in the wild, this may create crossing population growth TPCs consistent with adaptation to temperature. Future studies within this field should be more explicit in how they extrapolate from somatic growth in the lab to fitness in the wild.

• Bruijning, Marjolein; Fossen, Erlend Ignacio Fleck; Jongejans, Eelke; Vanvelk, Héléne; Raeymaekers, Joost A. M. & Govaert, Lynn [Vis alle 9 forfattere av denne artikkelen] (2021). Host–parasite dynamics shaped by temperature and genotype: Quantifying the role of underlying vital rates. Functional Ecology. ISSN 0269-8463. 36(2). doi: 10.1111/1365-2435.13966. Fulltekst i vitenarkiv Vis sammendrag

  Global warming challenges the persistence of local populations, not only through heat-induced stress, but also through indirect biotic changes. We study the interactive effects of temperature, competition and parasitism in the water flea Daphnia magna. We carried out a common garden experiment monitoring the dynamics of Daphnia populations along a temperature gradient. Halfway through the experiment, all populations became infected with the ectoparasite Amoebidium parasiticum, enabling us to study the interactive effects of temperature and parasite dynamics. We combined Integral Projection Models with epidemiological models, parameterized using the experimental data on the performance of individuals within dynamic populations. This enabled us to quantify the contribution of different vital rates and epidemiological parameters to population fitness across temperatures and Daphnia clones originating from two latitudes. Interactions between temperature and parasitism shaped competition, where Belgian clones performed better under infection than Norwegian clones. Infected Daphnia populations performed better at higher than at lower temperatures, mainly due to an increased host capability of reducing parasite loads. Temperature strongly affected individual vital rates, but effects largely cancelled out on a population-level. In contrast, parasitism strongly reduced fitness through consistent negative effects on all vital rates. As a result, temperature-mediated parasitism was more important than the direct effects of temperature in shaping population dynamics. Both the outcome of the competition treatments and the observed extinction patterns support our modelling results. Our study highlights that shifts in biotic interactions can be equally or more important for responses to warming than direct physiological effects of warming, emphasizing that we need to include such interactions in our studies to predict the competitive ability of natural populations experiencing global warming.

• Fossen, Erlend Ignacio Fleck; Raeymaekers, Joost A. M. & Einum, Sigurd (2021). Do genetic differences in growth thermal reaction norms maintain genetic variation in timing of diapause induction? Freshwater Biology. ISSN 0046-5070. 66(11), s. 2185–2195. doi: 10.1111/fwb.13825. Fulltekst i vitenarkiv Vis sammendrag

  An optimal timing for diapause induction through the sexual production of dormant propagules is expected in organisms with temporary populations. Yet, empirical studies often find high within-population genetic variation in the sexual production of such propagules, suggesting that this is a common feature of such organisms. Here, we hypothesize that genetic variation in the propensity to produce dormant propagules, Pd, is maintained by a genotype-by-environment interaction in clonal reproductive rates, where fast-growing genotypes within an environment should delay diapause relative to slow-growing genotypes. From this, we derive two predictions. First, if reaction norms of clonal reproduction cross between two environments, the genetic correlation of Pd between these environments should be negative. Second, the correlation between plasticity values of clonal reproduction and Pd should be negative. We tested these predictions by quantifying ephippia production in genotypes of a population of the facultative sexual cladoceran Daphnia magna at two temperatures. The population biomass at the onset of ephippia production was used as a measure of Pd, whereas juvenile somatic growth rate was used as a proxy for clonal reproductive rate. Plasticity for both measurements was derived from thermal reaction norms. Our results did not support either prediction, as neither the genetic correlation of Pd between environments, nor the correlation between plasticity values of growth and Pd were found to be significant. Our results suggest that genetic variation in the timing of diapause is not maintained by genetic differences in thermal clonal reproduction reaction norms. We propose as an alternative hypothesis that if there is variation across years in how the environment deteriorates over a season, fluctuating selection may favor genotypes with different Pd between years.

• Fossen, Erlend Ignacio Fleck; Pelabon, Christophe & Einum, Sigurd (2019). Genetic and environmental effects on the scaling of metabolic rate with body size. Journal of Experimental Biology. ISSN 0022-0949. 222, s. 1–7. doi: 10.1242/jeb.193243. Fulltekst i vitenarkiv Vis sammendrag

  Metabolic rate (MR) often scales with body mass (BM) following a power function of the form MR=aBMb, where log(a) is the allometric intercept and b is the allometric exponent (i.e. slope on a log–log scale). The variational properties of b have been debated, but very few studies have tested for genetic variance in b, and none have tested for a genotype-by-environment (G×E) interaction in b. Consequently, the short-term evolutionary potentials of both b and its phenotypic plasticity remain unknown. Using 10 clones of a population of Daphnia magna, we estimated the genetic variance in b and assessed whether a G×E interaction affected b. We measured MR on juveniles of different sizes reared and measured at three temperatures (17, 22 and 28°C). Overall, b decreased with increasing temperature. We found no evidence of genetic variance in b at any temperature, and thus no G×E interaction in b. However, we found a significant G×E interaction in size-specific MR. Using simulations, we show how this G×E interaction can generate genetic variation in the ontogenetic allometric slope of animals experiencing directional changes in temperature during growth. This suggests that b can evolve despite having limited genetic variation at constant temperatures.

• Einum, Sigurd; Fossen, Erlend Ignacio Fleck; Parry, Victor & Pelabon, Christophe (2019). Genetic Variation in Metabolic Rate and Correlations with Other Energy Budget Components and Life History in Daphnia magna. Evolutionary Biology. ISSN 0071-3260. 46(2), s. 170–178. doi: 10.1007/s11692-019-09473-x. Fulltekst i vitenarkiv Vis sammendrag

  Much is known about the genetic variance in certain components of metabolism, most notably resting and maximum metabolic rate. This is in stark contrast to the lack of information on genetic variance in the metabolic rate of individuals that feed and express routine activity, and how this rate correlates with other components of the energy budget or life history traits. Here we quantify genetic variance in metabolic rate (MR) under such conditions, as well as food consumption, juvenile somatic growth rate and age at maturation under ad lib food availability in a set of 10 clones of Daphnia magna from a natural population. Broad sense evolvabilities (0.16–0.56%) were on the same order of magnitude as those typically observed for physiological and life history traits, and suggest that all these traits have the potential to evolve within this population. We did not find support for the previously hypothesized positive genetic correlation between metabolic rate and growth rate. Rather, the patterns of genetic correlations suggest that genetic variance in food consumption is the single most influential trait shaping somatic growth rate, but that additional variance in growth can be explained by considering the joint effect of consumption and MR. The genetic variance in consumption and MR also translated into genetic variance in age at maturation, creating a direct link between these energy budget components and a life history trait with strong fitness effects. Moreover, a weak positive correlation between MR and food consumption suggests the presence of substantial amounts of independent genetic control of these traits, consistent with results obtained using genomic approaches.

• Fossen, Erlend Ignacio Fleck; Pelabon, Christophe & Einum, Sigurd (2018). An empirical test for a zone of canalization in thermal reaction norms. Journal of Evolutionary Biology. ISSN 1010-061X. 31(7), s. 936–943. doi: 10.1111/jeb.13287. Fulltekst i vitenarkiv Vis sammendrag

  Theoretical models on the evolution of phenotypic plasticity predict a zone of canalization where reaction norms cross, and genetic variation is minimized in the environment a population most frequently encounter. Empirical tests of this prediction are largely missing, in particular for life-history traits. We addressed this prediction by quantifying thermal reaction norms of three life-history traits (somatic growth rate, age and size at maturation) of a Norwegian population of Daphnia magna and testing for the occurrence of an intermediate temperature (Tm) at which genetic variance in the traits is minimized. Size at maturation changed relatively little with temperature compared to the other traits, and there was no genetic variance in the shape of the reaction norm. Consequently, age at maturation and somatic growth rate were strongly negatively correlated. Both traits showed a strong genotype–environment interaction, and the estimated Tm was 14 °C for both age at maturation and growth rate. This value of Tm corresponds well with mean summer temperatures experienced by the population and suggests that the population has evolved under stabilizing selection in temperatures that fluctuate around this mean temperature. These results suggest local adaptation to temperature in the studied population and allow predicting evolutionary trajectories of thermal reaction norms under changing thermal regimes.

• Yashchenko, Varvara; Fossen, Erlend Ignacio Fleck; Kielland, Øystein Nordeide & Einum, Sigurd (2016). Negative relationships between population density and metabolic rates are not general. Journal of Animal Ecology. ISSN 0021-8790. 85(4), s. 1070–1077. doi: 10.1111/1365-2656.12515. Fulltekst i vitenarkiv Vis sammendrag

  Population density has recently been suggested to be an important factor influencing metabolic rates and to represent an important ‘third axis’ explaining variation beyond that explained by body mass and temperature. In situations where population density influences food consumption, the immediate effect on metabolism acting through specific dynamic action (SDA), and downregulation due to fasting over longer periods, is well understood. However, according to a recent review, previous studies suggest a more general effect of population density per se, even in the absence of such effects. It has been hypothesized that this results from animals performing anticipatory responses (i.e. reduced activity) to expected declines in food availability. Here, we test the generality of this finding by measuring density effects on metabolic rates in 10 clones from two different species of the zooplankton Daphnia (Daphnia pulex Leydig and D. magna Straus). Using fluorescence-based respirometry, we obtain high-precision measures of metabolism. We also identify additional studies on this topic that were not included in the previous review, compare the results and evaluate the potential for measurement bias in all previous studies. We demonstrate significant variation in mass-specific metabolism among clones within both species. However, we find no evidence for a negative relationship between population density and mass-specific metabolism. The previously reported pattern also disappeared when we extended the set of studies analysed. We discuss potential reasons for the discrepancy among studies, including two main sources of potential bias (microbial respiration and declining oxygen consumption due to reduced oxygen availability). Only one of the previous studies gives sufficient information to conclude the absence of such biases, and consistent with our results, no effect of density on metabolism was found. We conclude that population density per se does not have a general effect on mass-specific metabolic rate.

• Fossen, Erlend Ignacio; Ekrem, Torbjørn; Nilsson, Anders N. & Bergsten, Johannes (2016). Species delimitation in northern European water scavenger beetles of the genus Hydrobius (Coleoptera, Hydrophilidae). ZooKeys. ISSN 1313-2989. 2016(564), s. 71–120. doi: 10.3897/zookeys.564.6558. Fulltekst i vitenarkiv Vis sammendrag

  The chiefly Holarctic Hydrobius species complex (Coleoptera, Hydrophilidae) currently consists of H. arcticus Kuwert, 1890, and three morphological variants of H. fuscipes (Linnaeus, 1758): var. fuscipes, var. rottenbergii and var. subrotundus in northern Europe. Here molecular and morphological data are used to test the species boundaries in this species complex. Three gene segments (COI, H3 and ITS2) were sequenced and analyzed with Bayesian methods to infer phylogenetic relationships. The Generalized Mixed Yule Coalescent (GMYC) model and two versions of the Bayesian species delimitation method BPP, with or without an a priori defined guide tree (v2.2 & v3.0), were used to evaluate species limits. External and male genital characters of primarily Fennoscandian specimens were measured and statistically analyzed to test for significant differences in quantitative morphological characters. The four morphotypes formed separate genetic clusters on gene trees and were delimited as separate species by GMYC and by both versions of BPP, despite specimens of H. f. var. fuscipes and H. f. var. subrotundus being sympatric. H. arcticus and H. f. var. rottenbergii could only be separated genetically with ITS2, and were delimited statistically with GMYC on ITS2 and with BPP on the combined data. In addition, six or seven potentially cryptic species of the H. fuscipes complex from regions outside northern Europe were delimited genetically. Although some overlap was found, the mean values of six male genital characters were significantly different between the morphotypes (p < 0.001). Morphological characters previously presumed to be diagnostic were less reliable to separate H. f. var. fuscipes from H. f. var. subrotundus, but characters in the literature for H. arcticus and H. f. var. rottenbergii were diagnostic. Overall, morphological and molecular evidence strongly suggest that H. arcticus and the three morphological variants of H. fuscipes are separate species and Hydrobius rottenbergii Gerhardt, 1872, stat. n. and Hydrobius subrotundus Stephens, 1829, stat. n. are elevated to valid species. An identification key to northern European species of Hydrobius is provided.

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• Fossen, Erlend I. F.; Chowdhury, Sourangsu; Marginean, Iulia; Kapwata, Thandi; Wright, Caradee & Aunan, Kristin (2025). Health Impacts of PM2.5 Pollution in South Africa: A High-Resolution Exposure-Response Assessment. Fulltekst i vitenarkiv
• Fossen, Erlend I. F. & Aunan, Kristin (2025). A review of interaction effects of air pollution and non-optimal temperature on mortality and morbidity. Fulltekst i vitenarkiv
• Fossen, Erlend I. F. & Aunan, Kristin (2025). A Review of Interaction Effects of Air Pollution and Non-Optimal Temperature on Mortality and Morbidity. Fulltekst i vitenarkiv
• Fossen, Erlend I. F. (2025). Using machine learning to predict vector-borne diseases in a changing climate. Fulltekst i vitenarkiv
• Bjerkaas, Mette; Fossen, Erlend I. F. & Reiersen, Frederick (2025). Klimakrisen sett med barns øyne - rettigheter, bekymringer og håp. doi: https:/www.reddbarna.no/content/uploads/2021/01/Klimakrisen-sett-med-barns-oyne-1.pdf. Fulltekst i vitenarkiv
• Fossen, Erlend Ignacio; Raeymaekers, Joost A. M. & Einum, Sigurd (2017). Predicting the onset of winter: genetic variance in optimism in Daphnia. Fulltekst i vitenarkiv
• Fossen, Erlend Ignacio; Pelabon, Christophe & Einum, Sigurd (2016). Potential for evolution of thermal reaction norms. Fulltekst i vitenarkiv
• Vaagland, Henriette; Olufsen, Marianne Opsahl; Førde, Marian; Evertsen, Jussi; Gagnat, Maren Ranheim & Løseth, Mari Engvig [Vis alle 9 forfattere av denne artikkelen] (2014). Havsprell - verdt en snap! Fulltekst i vitenarkiv Vis sammendrag

  Møt rognkjeksbabier med sugekopp på magen, en eremittkreps med en brennhet samboer og ta på store krabber, sjøpølser og andre spennende dyr fra Trondheimsfjorden. Sjekk hvordan dyr og planter egentlig ser ut på virkelig nært hold - under mikroskopet. Her er det kommunikasjon på alle nivå!

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