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Publications (10 of 84) Show all publications
Roy, S., Brännström, Å. & Dieckmann, U. (2024). Ecological determinants of Cope’s rule and its inverse. Communications Biology, 7(1), Article ID 38.
Open this publication in new window or tab >>Ecological determinants of Cope’s rule and its inverse
2024 (English)In: Communications Biology, E-ISSN 2399-3642, Vol. 7, no 1, article id 38Article in journal (Refereed) Published
Abstract [en]

Cope’s rule posits that evolution gradually increases the body size in lineages. Over the last decades, two schools of thought have fueled a debate on the applicability of Cope’s rule by reporting empirical evidence, respectively, for and against Cope’s rule. The apparent contradictions thus documented highlight the need for a comprehensive process-based synthesis through which both positions of this debate can be understood and reconciled. Here, we use a process-based community-evolution model to investigate the eco-evolutionary emergence of Cope’s rule. We report three characteristic macroevolutionary patterns, of which only two are consistent with Cope’s rule. First, we find that Cope’s rule applies when species interactions solely depend on relative differences in body size and the risk of lineage extinction is low. Second, in environments with higher risk of lineage extinction, the recurrent evolutionary elimination of top predators induces cyclic evolution toward larger body sizes, according to a macroevolutionary pattern we call the recurrent Cope’s rule. Third, when interactions between species are determined not only by their body sizes but also by their ecological niches, the recurrent Cope’s rule may get inverted, leading to cyclic evolution toward smaller body sizes. This recurrent inverse Cope’s rule is characterized by highly dynamic community evolution, involving the diversification of species with large body sizes and the extinction of species with small body sizes. To our knowledge, these results provide the first theoretical foundation for reconciling the contrasting empirical evidence reported on body-size evolution.

Place, publisher, year, edition, pages
Nature Publishing Group, 2024
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:umu:diva-220168 (URN)10.1038/s42003-023-05375-z (DOI)001144696300001 ()38238502 (PubMedID)2-s2.0-85182687615 (Scopus ID)
Funder
European CommissionEuropean Science Foundation (ESF)
Available from: 2024-02-05 Created: 2024-02-05 Last updated: 2024-02-05Bibliographically approved
Andersson, B., Zhao, W., Haller, B. C., Brännström, Å. & Wang, X.-R. (2023). Inference of the distribution of fitness effects of mutations is affected by single nucleotide polymorphism filtering methods, sample size and population structure. Molecular Ecology Resources, 23(7), 1589-1603
Open this publication in new window or tab >>Inference of the distribution of fitness effects of mutations is affected by single nucleotide polymorphism filtering methods, sample size and population structure
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2023 (English)In: Molecular Ecology Resources, ISSN 1755-098X, E-ISSN 1755-0998, Vol. 23, no 7, p. 1589-1603Article in journal (Refereed) Published
Abstract [en]

The distribution of fitness effects (DFE) of new mutations has been of interest to evolutionary biologists since the concept of mutations arose. Modern population genomic data enable us to quantify the DFE empirically, but few studies have examined how data processing, sample size and cryptic population structure might affect the accuracy of DFE inference. We used simulated and empirical data (from Arabidopsis lyrata) to show the effects of missing data filtering, sample size, number of single nucleotide polymorphisms (SNPs) and population structure on the accuracy and variance of DFE estimates. Our analyses focus on three filtering methods—downsampling, imputation and subsampling—with sample sizes of 4–100 individuals. We show that (1) the choice of missing-data treatment directly affects the estimated DFE, with downsampling performing better than imputation and subsampling; (2) the estimated DFE is less reliable in small samples (<8 individuals), and becomes unpredictable with too few SNPs (<5000, the sum of 0- and 4-fold SNPs); and (3) population structure may skew the inferred DFE towards more strongly deleterious mutations. We suggest that future studies should consider downsampling for small data sets, and use samples larger than 4 (ideally larger than 8) individuals, with more than 5000 SNPs in order to improve the robustness of DFE inference and enable comparative analyses.

Place, publisher, year, edition, pages
John Wiley & Sons, 2023
Keywords
DFE, missing-data treatment, population structure, sample size, SLiM simulation
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:umu:diva-211803 (URN)10.1111/1755-0998.13825 (DOI)001015493200001 ()37340611 (PubMedID)2-s2.0-85162975600 (Scopus ID)
Funder
Swedish Research CouncilSwedish National Infrastructure for Computing (SNIC)
Available from: 2023-07-11 Created: 2023-07-11 Last updated: 2024-01-10Bibliographically approved
Isaksson, H., Brännström, Å. & Libby, E. (2023). Minor variations in multicellular life cycles have major effects on adaptation. PloS Computational Biology, 19(4), Article ID e1010698.
Open this publication in new window or tab >>Minor variations in multicellular life cycles have major effects on adaptation
2023 (English)In: PloS Computational Biology, ISSN 1553-734X, E-ISSN 1553-7358, Vol. 19, no 4, article id e1010698Article in journal (Refereed) Published
Abstract [en]

Multicellularity has evolved several independent times over the past hundreds of millions of years and given rise to a wide diversity of complex life. Recent studies have found that large differences in the fundamental structure of early multicellular life cycles can affect fitness and influence multicellular adaptation. Yet, there is an underlying assumption that at some scale or categorization multicellular life cycles are similar in terms of their adaptive potential. Here, we consider this possibility by exploring adaptation in a class of simple multicellular life cycles of filamentous organisms that only differ in one respect, how many daughter filaments are produced. We use mathematical models and evolutionary simulations to show that despite the similarities, qualitatively different mutations fix. In particular, we find that mutations with a tradeoff between cell growth and group survival, i.e. "selfish" or "altruistic" traits, spread differently. Specifically, altruistic mutations more readily spread in life cycles that produce few daughters while in life cycles producing many daughters either type of mutation can spread depending on the environment. Our results show that subtle changes in multicellular life cycles can fundamentally alter adaptation.

National Category
Evolutionary Biology
Identifiers
urn:nbn:se:umu:diva-209284 (URN)10.1371/journal.pcbi.1010698 (DOI)000974421200004 ()37083675 (PubMedID)2-s2.0-85159546634 (Scopus ID)
Funder
Swedish Research Council, 2018-0363
Available from: 2023-06-08 Created: 2023-06-08 Last updated: 2023-06-08Bibliographically approved
Brännström, Å., Sjödin, H. & Rocklöv, J. (2022). A Method for Estimating the Number of Infections From the Reported Number of Deaths. Frontiers In Public Health, 9, Article ID 648545.
Open this publication in new window or tab >>A Method for Estimating the Number of Infections From the Reported Number of Deaths
2022 (English)In: Frontiers In Public Health, ISSN 2296-2565, Vol. 9, article id 648545Article in journal (Refereed) Published
Abstract [en]

At the outset of an epidemic, available case data typically underestimate the total number of infections due to insufficient testing, potentially hampering public responses. Here, we present a method for statistically estimating the true number of cases with confidence intervals from the reported number of deaths and estimates of the infection fatality ratio; assuming that the time from infection to death follows a known distribution. While the method is applicable to any epidemic with a significant mortality rate, we exemplify the method by applying it to COVID-19. Our findings indicate that the number of unreported COVID-19 infections in March 2020 was likely to be at least one order of magnitude higher than the reported cases, with the degree of underestimation among the countries considered being particularly high in the United Kingdom.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2022
Keywords
COVID-19, estimating, infectives, nowcasting, surveillance
National Category
Public Health, Global Health, Social Medicine and Epidemiology Probability Theory and Statistics
Identifiers
urn:nbn:se:umu:diva-192376 (URN)10.3389/fpubh.2021.648545 (DOI)35111706 (PubMedID)2-s2.0-85123950757 (Scopus ID)
Available from: 2022-02-11 Created: 2022-02-11 Last updated: 2022-02-11Bibliographically approved
Aye, T. N., Brännström, Å. & Carlsson, L. (2022). Prediction of tree sapwood and heartwood profiles using pipe model and branch thinning theory. Tree Physiology, 42(11), 2174-2185
Open this publication in new window or tab >>Prediction of tree sapwood and heartwood profiles using pipe model and branch thinning theory
2022 (English)In: Tree Physiology, ISSN 0829-318X, E-ISSN 1758-4469, Vol. 42, no 11, p. 2174-2185Article in journal (Refereed) Published
Abstract [en]

Estimates of tree heartwood and sapwood profiles are important in the pulp industry and for dynamic vegetation models, in which they determine tree biomechanical stability and hydraulic conductivity. Several phenomenological models of stem profiles have been developed for this purpose, based on assumptions on how tree crown and foliage distributions change over time. Here, we derive estimates of tree profiles by synthesizing a simple pipe model theory of plant form with a recently developed theory of branch thinning that from simple assumptions quantifies discarded branches and leaves. This allows us to develop a new trunk model of tree profiles from breast height up to the top of the tree. We postulate that leaves that are currently on the tree are connected by sapwood pipes, while pipes that previously connected discarded leaves or branches form the heartwood. By assuming that a fixed fraction of all pipes remain on the trunk after a branching event, as the trunk is traversed from the root system to the tips, this allows us to quantify trunk heartwood and sapwood profiles. We test the trunk model performance on empirical data from five tree species across three continents. We find that the trunk model accurately describes heartwood and sapwood profiles of all tested tree species (calibration; R2: 84-99%). Furthermore, once calibrated to a tree species, the trunk model predicts heartwood and sapwood profiles of conspecific trees in similar growing environments based only on the age and height of a tree (cross-validation/prediction; R2: 68-98%). The fewer and often contrasting parameters needed for the trunk model make it a potentially useful complementary tool for biologists and foresters.

Place, publisher, year, edition, pages
Oxford University Press, 2022
Keywords
branch thinning model, heartwood, Huber value, pipe model, sapwood, trunk model
National Category
Forest Science
Identifiers
urn:nbn:se:umu:diva-201349 (URN)10.1093/treephys/tpac065 (DOI)000840880200001 ()35849036 (PubMedID)2-s2.0-85141933658 (Scopus ID)
Available from: 2022-12-14 Created: 2022-12-14 Last updated: 2022-12-14Bibliographically approved
Żebrowski, P., Dieckmann, U., Brännström, Å., Franklin, O. & Rovenskaya, E. (2022). Sharing the Burdens of Climate Mitigation and Adaptation: Incorporating Fairness Perspectives into Policy Optimization Models. Sustainability, 14(7), Article ID 3737.
Open this publication in new window or tab >>Sharing the Burdens of Climate Mitigation and Adaptation: Incorporating Fairness Perspectives into Policy Optimization Models
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2022 (English)In: Sustainability, E-ISSN 2071-1050, Vol. 14, no 7, article id 3737Article in journal (Refereed) Published
Abstract [en]

Mitigation of, and adaptation to, climate change can be addressed only through the collective action of multiple agents. The engagement of involved agents critically depends on their perception that the burdens and benefits of collective action are distributed fairly. Integrated Assessment Models (IAMs), which inform climate policies, focus on the minimization of costs and the maximization of overall utility, but they rarely pay sufficient attention to how costs and benefits are distributed among agents. Consequently, some agents may perceive the resultant model-based policy recommendations as unfair. In this paper, we propose how to adjust the objectives optimized within IAMs so as to derive policy recommendations that can plausibly be presented to agents as fair. We review approaches to aggregating the utilities of multiple agents into fairness-relevant social rankings of outcomes, analyze features of these rankings, and associate with them collections of properties that a model’s objective function must have to operationalize each of these rankings within the model. Moreover, for each considered ranking, we propose a selection of specific objective functions that can conveniently be used for generating this ranking in a model. Maximizing these objective functions within existing IAMs allows exploring and identifying climate polices to which multiple agents may be willing to commit.

Place, publisher, year, edition, pages
MDPI, 2022
Keywords
aggregating functions, burden sharing, fairness, multi-objective optimization, Pareto optimality, policy optimization models
National Category
Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-193801 (URN)10.3390/su14073737 (DOI)000782001200001 ()2-s2.0-85127435104 (Scopus ID)
Funder
EU, Horizon 2020, 820989
Available from: 2022-05-06 Created: 2022-05-06 Last updated: 2022-05-06Bibliographically approved
Jang, Y.-T., Brännström, Å. & Pontarp, M. (2022). The interactive effects of environmental gradient and dispersal shape spatial phylogenetic patterns. Frontiers in Ecology and Evolution, 10, Article ID 1037980.
Open this publication in new window or tab >>The interactive effects of environmental gradient and dispersal shape spatial phylogenetic patterns
2022 (English)In: Frontiers in Ecology and Evolution, E-ISSN 2296-701X, Vol. 10, article id 1037980Article in journal (Refereed) Published
Abstract [en]

Introduction: The emergence and maintenance of biodiversity include interacting environmental conditions, organismal adaptation to such conditions, and dispersal. To understand and quantify such ecological, evolutionary, and spatial processes, observation and interpretation of phylogenetic relatedness across space (e.g., phylogenetic beta diversity) is arguably a way forward as such patterns contain signals from all the processes listed above. However, it remains challenging to extract information about complex eco-evolutionary and spatial processes from phylogenetic patterns.

Methods: We link environmental gradients and organismal dispersal with phylogenetic beta diversity using a trait-based and eco-evolutionary model of diversification along environmental gradients. The combined effect of the environment and dispersal leads to distinct phylogenetic patterns between subsets of species and across geographical distances.

Results and discussion: Steep environmental gradients combined with low dispersal lead to asymmetric phylogenies, a high phylogenetic beta diversity, and the phylogenetic diversity between communities increases linearly along the environmental gradient. High dispersal combined with a less steep environmental gradient leads to symmetric phylogenies, low phylogenetic beta diversity, and the phylogenetic diversity between communities along the gradient increases in a sigmoidal form. By disentangling the eco-evolutionary mechanisms that link such interacting environment and dispersal effects and community phylogenetic patterns, our results improve understanding of biodiversity in general and help interpretation of observed phylogenetic beta diversity.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2022
Keywords
adaptive radiation, dispersal, environmental gradient, phylogenetic beta diversity, phylogenetic patterns
National Category
Evolutionary Biology Biological Systematics Other Mathematics
Identifiers
urn:nbn:se:umu:diva-202230 (URN)10.3389/fevo.2022.1037980 (DOI)000904798800001 ()2-s2.0-85145029730 (Scopus ID)
Available from: 2023-01-09 Created: 2023-01-09 Last updated: 2023-09-05Bibliographically approved
Fransson, P., Brännström, Å. & Franklin, O. (2021). A tree’s quest for light: optimal height and diameter growth under a shading canopy. Tree Physiology, 41(1), 1-11
Open this publication in new window or tab >>A tree’s quest for light: optimal height and diameter growth under a shading canopy
2021 (English)In: Tree Physiology, ISSN 0829-318X, E-ISSN 1758-4469, Vol. 41, no 1, p. 1-11Article in journal (Refereed) Published
Abstract [en]

For trees in forests, striving for light is matter of life and death, either by growing taller toward brighter conditions or by expanding the crown to capture more of the available light. Here, we present a mechanistic model for the development path of stem height and crown size, accounting for light capture and growth, as well as mortality risk. We determine the optimal growth path among all possible trajectories using dynamic programming. The optimal growth path follows a sequence of distinct phases: (i) initial crown size expansion, (ii) stem height growth toward the canopy, (iii) final expansion of the crown in the canopy and (iv) seed production without further increase in size. The transition points between these phases can be optimized by maximizing fitness, defined as expected lifetime reproductive production. The results imply that to reach the canopy in an optimal way, trees must consider the full profile of expected increasing light levels toward the canopy. A shortsighted maximization of growth based on initial light conditions can result in arrested height growth, preventing the tree from reaching the canopy. The previous result can explain canopy stratification, and why canopy species often get stuck at a certain size under a shading canopy. The model explains why trees with lower wood density have a larger diameter at a given tree height and grow taller than trees with higher wood density. The model can be used to implement plasticity in height versus diameter growth in individual-based vegetation and forestry models.

Keywords
Allocation, Growth strategy, Life history, Optimal control, Tree
National Category
Ecology
Research subject
biology
Identifiers
urn:nbn:se:umu:diva-156734 (URN)10.1093/treephys/tpaa110 (DOI)000612199200001 ()2-s2.0-85100069843 (Scopus ID)
Funder
Swedish Research Council Formas, 2012-1008Wallenberg Foundations
Note

Originally included in thesis in manuscript form.

Available from: 2019-02-26 Created: 2019-02-26 Last updated: 2023-09-05Bibliographically approved
Harrison, S. P., Cramer, W., Franklin, O., Prentice, I. C., Wang, H., Brännström, Å., . . . Wright, I. J. (2021). Eco-evolutionary optimality as a means to improve vegetation and land-surface models. New Phytologist, 231(6), 2125-2141
Open this publication in new window or tab >>Eco-evolutionary optimality as a means to improve vegetation and land-surface models
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2021 (English)In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 231, no 6, p. 2125-2141Article, review/survey (Refereed) Published
Abstract [en]

Global vegetation and land-surface models embody interdisciplinary scientific understanding of the behaviour of plants and ecosystems, and are indispensable to project the impacts of environmental change on vegetation and the interactions between vegetation and climate. However, systematic errors and persistently large differences among carbon and water cycle projections by different models highlight the limitations of current process formulations. In this review, focusing on core plant functions in the terrestrial carbon and water cycles, we show how unifying hypotheses derived from eco-evolutionary optimality (EEO) principles can provide novel, parameter-sparse representations of plant and vegetation processes. We present case studies that demonstrate how EEO generates parsimonious representations of core, leaf-level processes that are individually testable and supported by evidence. EEO approaches to photosynthesis and primary production, dark respiration and stomatal behaviour are ripe for implementation in global models. EEO approaches to other important traits, including the leaf economics spectrum and applications of EEO at the community level are active research areas. Independently tested modules emerging from EEO studies could profitably be integrated into modelling frameworks that account for the multiple time scales on which plants and plant communities adjust to environmental change.

Place, publisher, year, edition, pages
New Phytologist Foundation, 2021
Keywords
acclimation, eco-evolutionary optimality, global vegetation model, land-surface model, leaf economics spectrum, plant functional ecology, stomatal behaviour, water and carbon trade-offs
National Category
Botany
Identifiers
urn:nbn:se:umu:diva-186470 (URN)10.1111/nph.17558 (DOI)000675158800001 ()34131932 (PubMedID)2-s2.0-85110986439 (Scopus ID)
Funder
Swedish Research Council Formas, 2016‐00998Knut and Alice Wallenberg Foundation
Available from: 2021-08-03 Created: 2021-08-03 Last updated: 2023-03-24Bibliographically approved
Hofhansl, F., Chacón-Madrigal, E., Brännström, Å., Dieckmann, U. & Franklin, O. (2021). Mechanisms driving plant functional trait variation in a tropical forest. Ecology and Evolution, 11(9), 3856-3870
Open this publication in new window or tab >>Mechanisms driving plant functional trait variation in a tropical forest
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2021 (English)In: Ecology and Evolution, E-ISSN 2045-7758, Vol. 11, no 9, p. 3856-3870Article in journal (Refereed) Published
Abstract [en]

Plant functional trait variation in tropical forests results from taxonomic differences in phylogeny and associated genetic differences, as well as, phenotypic plastic responses to the environment. Accounting for the underlying mechanisms driving plant functional trait variation is important for understanding the potential rate of change of ecosystems since trait acclimation via phenotypic plasticity is very fast compared to shifts in community composition and genetic adaptation. We here applied a statistical technique to decompose the relative roles of phenotypic plasticity, genetic adaptation, and phylogenetic constraints. We examined typically obtained plant functional traits, such as wood density, plant height, specific leaf area, leaf area, leaf thickness, leaf dry mass content, leaf nitrogen content, and leaf phosphorus content. We assumed that genetic differences in plant functional traits between species and genotypes increase with environmental heterogeneity and geographic distance, whereas trait variation due to plastic acclimation to the local environment is independent of spatial distance between sampling sites. Results suggest that most of the observed trait variation could not be explained by the measured environmental variables, thus indicating a limited potential to predict individual plant traits from commonly assessed parameters. However, we found a difference in the response of plant functional traits, such that leaf traits varied in response to canopy-light regime and nutrient availability, whereas wood traits were related to topoedaphic factors and water availability. Our analysis furthermore revealed differences in the functional response of coexisting neotropical tree species, which suggests that endemic species with conservative ecological strategies might be especially prone to competitive exclusion under projected climate change.

Place, publisher, year, edition, pages
John Wiley & Sons, 2021
Keywords
Biodiversity, climate change, Costa Rica, plant functional traits, tropical forest
National Category
Ecology Botany
Identifiers
urn:nbn:se:umu:diva-181841 (URN)10.1002/ece3.7256 (DOI)000628452600001 ()2-s2.0-85102477320 (Scopus ID)
Available from: 2021-04-06 Created: 2021-04-06 Last updated: 2024-01-17Bibliographically approved
Projects
Precision forestry for the future: enhanced forest management by optimized tree selection in thinning operations [2012-1008_Formas]; Umeå UniversityEvolution in spatially-structured populations [2015-03917_VR]; Umeå University
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9862-816x

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