SwePub - sökning: WFRF:(Barabas György)

Numrering	Referens	Omslagsbild	Hitta
1.	Aoyama, Lina, et al. (författare) Application of modern coexistence theory to rare plant restoration provides early indication of restoration trajectories 2022 Ingår i: Ecological Applications. - : Wiley. - 1051-0761 .- 1939-5582. ; 32:7 Tidskriftsartikel (refereegranskat)abstract Restoration ecology commonly seeks to re-establish species of interest in degraded habitats. Despite a rich understanding of how succession influences re-establishment, there are several outstanding questions that remain unaddressed: are short-term abundances sufficient to determine long-term re-establishment success, and what factors contribute to unpredictable restorations outcomes? In other words, when restoration fails, is it because the restored habitat is substandard, because of strong competition with invasive species, or alternatively due to changing environmental conditions that would equally impact established populations? Here, we re-purpose tools developed from modern coexistence theory to address these questions, and apply them to an effort to restore the endangered Contra Costa goldfields (Lasthenia conjugens) in constructed ("restored") California vernal pools. Using 16 years of data, we construct a population model of L. conjugens, a species of conservation concern due primarily to habitat loss and invasion of exotic grasses. We show that initial, short-term appearances of restoration success from population abundances is misleading, as year-to-year fluctuations cause long-term population growth rates to fall below zero. The failure of constructed pools is driven by lower maximum growth rates compared with reference ("natural") pools, coupled with a stronger negative sensitivity to annual fluctuations in abiotic conditions that yield decreased maximum growth rates. Nonetheless, our modeling shows that fluctuations in competition (mainly with exotic grasses) benefit L. conjugens through periods of competitive release, especially in constructed pools of intermediate pool depth. We therefore show how reductions in invasives and seed addition in pools of particular depths could change the outcome of restoration for L. conjugens. By applying a largely theoretical framework to the urgent goal of ecological restoration, our study provides a blueprint for predicting restoration success, and identifies future actions to reverse species loss.
2.	Arnoldi, Jean-Francois, et al. (författare) Invasions of ecological communities : Hints of impacts in the invaders growth rate 2022 Ingår i: Methods in Ecology and Evolution. - : Wiley. - 2041-210X. ; 13:1, s. 167-182 Tidskriftsartikel (refereegranskat)abstract 1. Theory in ecology and evolution often relies on the analysis of invasion processes, and general approaches exist to understand the early stages of an invasion. However, predicting the long-term transformations of communities following an invasion remains a challenging endeavour. 2. We propose a general analytical method that uses both resident community and invader dynamical features to predict whether an invasion causes large long-term impacts on the invaded community. 3. This approach reveals a direction in which classic invasion analysis, based on initial invasion growth rate, can be extended. Indeed, we explain how the density dependence of invasion growth, if properly defined, synthetically encodes the long-term biotic transformations caused by an invasion, and therefore predicts its ultimate outcome. This approach further clarifies how the density dependence of the invasion growth rate is as much a property of the invading population as it is one of the invaded community. 4. Our theory applies to any stable community model, and directs us towards new questions that may enrich the toolset of invasion analysis, and suggests that indirect interactions and dynamical stability are key determinants of invasion outcomes.
3.	Barabas, György (författare) Biodiversity and community structure 2021 Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 118:11 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract n/a
4.	Barabas, György, et al. (författare) Chesson's coexistence theory 2018 Ingår i: Ecological Monographs. - : WILEY. - 0012-9615 .- 1557-7015. ; 88:3, s. 277-303 Forskningsöversikt (refereegranskat)abstract We give a comprehensive review of Chesson's coexistence theory, summarizing, for the first time, all its fundamental details in one single document. Our goal is for both theoretical and empirical ecologists to be able to use the theory to interpret their findings, and to get a precise sense of the limits of its applicability. To this end, we introduce an explicit handling of limiting factors, and a new way of defining the scaling factors that partition invasion growth rates into the different mechanisms contributing to coexistence. We explain terminology such as relative nonlinearity, storage effect, and growth-density covariance, both in a formal setting and through their biological interpretation. We review the theory's applications and contributions to our current understanding of species coexistence. While the theory is very general, it is not well suited to all problems, so we carefully point out its limitations. Finally, we critique the paradigm of decomposing invasion growth rates into stabilizing and equalizing components: we argue that these concepts are useful when used judiciously, but have often been employed in an overly simplified way to justify false claims.
5.	Barabas, György, et al. (författare) Chessons coexistence theory: reply 2020 Ingår i: Ecology. - : John Wiley & Sons. - 0012-9658 .- 1939-9170. ; 101:11 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract n/a
6.	Barabas, György (författare) Parameter Sensitivity of Transient Community Dynamics 2024 Ingår i: American Naturalist. - : UNIV CHICAGO PRESS. - 0003-0147 .- 1537-5323. Tidskriftsartikel (refereegranskat)abstract Transient dynamics have always intrigued ecologists, but current rapid environmental change (inducing transients even in previously undisturbed systems) has highlighted their importance more than ever. Here, I introduce a method for analyzing the sensitivity of transient ecological dynamics to parameter perturbations. The question the method answers is: how would the community dynamics have unfolded for some time horizon had the parameters been slightly different? I apply the method to three empirically parameterized models: competition between native forbs and exotic grasses in California, a host-parasitoid system, and an experimental chemostat predator-prey model. These applications showcase the ecological insights one can gain from models using transient sensitivity analysis. First, one can find parameters and their combinations whose perturbations disproportionately affect a system. Second, one can identify particular windows of time during which the predicted deviation from the unperturbed trajectories is especially large and utilize this information for management purposes. Third, there is an inverse relationship between transient and long-term sensitivities whenever the interacting populations are ecologically similar; paradoxically, the smaller the immediate response of the system, the more extreme its long-term response will be.
7.	Barabas, György, et al. (författare) Self-regulation and the stability of large ecological networks 2017 Ingår i: NATURE ECOLOGY and EVOLUTION. - : NATURE PUBLISHING GROUP. - 2397-334X. ; 1:12, s. 1870- Tidskriftsartikel (refereegranskat)abstract The stability of complex ecological networks depends both on the interactions between species and the direct effects of the species on themselves. These self-effects are known as self-regulation when an increase in a species abundance decreases its per-capita growth rate. Sources of self-regulation include intraspecific interference, cannibalism, time-scale separation between consumers and their resources, spatial heterogeneity and nonlinear functional responses coupling predators with their prey. The influence of self-regulation on network stability is understudied and in addition, the empirical estimation of self-effects poses a formidable challenge. Here, we show that empirical food web structures cannot be stabilized unless the majority of species exhibit substantially strong self-regulation. We also derive an analytical formula predicting the effect of self-regulation on network stability with high accuracy and show that even for random networks, as well as networks with a cascade structure, stability requires negative self-effects for a large proportion of species. These results suggest that the aforementioned potential mechanisms of self-regulation are probably more important in contributing to the stability of observed ecological networks than was previously thought.
8.	Barabas, György (författare) The coexistence problem revisited 2017 Ingår i: NATURE ECOLOGY and EVOLUTION. - : NATURE PUBLISHING GROUP. - 2397-334X. ; 1:10, s. 1425-1426 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract A new theoretical study warns against common misinterpretations of classical ideas on the limits to species diversity.
9.	Barabas, György, et al. (författare) The evolution of trait variance creates a tension between species diversity and functional diversity 2022 Ingår i: Nature Communications. - : Nature Portfolio. - 2041-1723. ; 13:1 Tidskriftsartikel (refereegranskat)abstract It seems intuitively obvious that species diversity promotes functional diversity: communities with more plant species imply more varied plant leaf chemistry, more species of crops provide more kinds of food, etc. Recent literature has nuanced this view, showing how the relationship between the two can be modulated along latitudinal or environmental gradients. Here we show that even without such effects, the evolution of functional trait variance can erase or even reverse the expected positive relationship between species- and functional diversity. We present theory showing that trait-based eco-evolutionary processes force species to evolve narrower trait breadths in more tightly packed, species-rich communities, in their effort to avoid competition with neighboring species. This effect is so strong that it leads to an overall reduction in trait space coverage whenever a new species establishes. Empirical data from land snail communities on the Galapagos Islands are consistent with this claim. The finding that the relationship between species- and functional diversity can be negative implies that trait data from species-poor communities may misjudge functional diversity in species-rich ones, and vice versa. The positive relationship between species diversity and functional diversity has been shown to vary. Here, the authors use theoretical models and data from Galapagos land snail communities to show how eco-evolutionary processes can force species to evolve narrower trait breadths in more species-rich communities to avoid competition, creating a negative relationship.
10.	Barabas, György, 1983-, et al. (författare) Using Quotas as a Remedy for Structural Injustice 2023 Ingår i: Erkenntnis. - : Springer. - 0165-0106 .- 1572-8420. ; 88, s. 3631-3649 Tidskriftsartikel (refereegranskat)abstract We analyze a frequent but undertheorized form of structural injustice, one that arises due to the difficulty of reaching numerically equitable representation of underrepresented subgroups within a larger group. This form of structural injustice is significant because it could occur even if it were possible to completely eliminate bias and overt discrimination from hiring and recruitment practices. The conceptual toolkit we develop can be used to analyze such situations and propose remedies. Specifically, based on a simple mathematical model, we offer a new argument in favour of quotas, explore implications for policy-making, and consider the wider philosophical significance of the problem. We show that in order to reach more equitable representations, quota-based recruitment may often be practically unavoidable. Assuming that members of groups in statistical minority are more likely to quit due to their marginalization, their proportions can stabilize at a low level, preventing a shift towards more equal representation and conserving the minority status of the subgroup. We show that this argument has important implications for addressing, preventing, and remediating the structural injustice of unfair representation.
11.	Boza, G., et al. (författare) Eco-evolutionary modelling of microbial syntrophy indicates the robustness of cross-feeding over cross-facilitation 2023 Ingår i: Scientific Reports. - : NATURE PORTFOLIO. - 2045-2322. ; 13:1 Tidskriftsartikel (refereegranskat)abstract Syntrophic cooperation among prokaryotes is ubiquitous and diverse. It relies on unilateral or mutual aid that may be both catalytic and metabolic in nature. Hypotheses of eukaryotic origins claim that mitochondrial endosymbiosis emerged from mutually beneficial syntrophy of archaeal and bacterial partners. However, there are no other examples of prokaryotic syntrophy leading to endosymbiosis. One potential reason is that when externalized products become public goods, they incite social conflict due to selfish mutants that may undermine any mutualistic interactions. To rigorously evaluate these arguments, here we construct a general mathematical framework of the ecology and evolution of different types of syntrophic partnerships. We do so both in a general microbial and in a eukaryogenetic context. Studying the case where partners cross-feed on each others self-inhibiting waste, we show that cooperative partnerships will eventually dominate over selfish mutants. By contrast, systems where producers actively secrete enzymes that cross-facilitate their partners resource consumption are not robust against cheaters over evolutionary time. We conclude that cross-facilitation is unlikely to provide an adequate syntrophic origin for endosymbiosis, but that cross-feeding mutualisms may indeed have played that role.
12.	Carpentier, Camille, et al. (författare) Reinterpreting the relationship between number of species and number of links connects community structure and stability 2021 Ingår i: Nature Ecology & Evolution. - : Springer Nature. - 2397-334X. ; 5:8, s. 1102-1109 Tidskriftsartikel (refereegranskat)abstract For 50 years, ecologists have examined how the number of interactions (links) scales with the number of species in ecological networks. Here, we show that the way the number of links varies when species are sequentially removed from a community is fully defined by a single parameter identifiable from empirical data. We mathematically demonstrate that this parameter is network-specific and connects local stability and robustness, establishing a formal connection between community structure and two prime stability concepts. Importantly, this connection highlights a local stability-robustness trade-off, which is stronger in mutualistic than in trophic networks. Analysis of 435 empirical networks confirmed these results. We finally show how our network-specific approach relates to the classical across-network approach found in literature. Taken together, our results elucidate one of the intricate relationships between network structure and stability in community networks. This paper demonstrates that the scaling relationship between the number of species and the number of interactions (links) in a network can explain its local stability and robustness to secondary extinctions.
13.	Clark, Adam Thomas, et al. (författare) General statistical scaling laws for stability in ecological systems 2021 Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 24:7, s. 1474-1486 Tidskriftsartikel (refereegranskat)abstract Ecological stability refers to a family of concepts used to describe how systems of interacting species vary through time and respond to disturbances. Because observed ecological stability depends on sampling scales and environmental context, it is notoriously difficult to compare measurements across sites and systems. Here, we apply stochastic dynamical systems theory to derive general statistical scaling relationships across time, space, and ecological level of organisation for three fundamental stability aspects: resilience, resistance, and invariance. These relationships can be calibrated using random or representative samples measured at individual scales, and projected to predict average stability at other scales across a wide range of contexts. Moreover deviations between observed vs. extrapolated scaling relationships can reveal information about unobserved heterogeneity across time, space, or species. We anticipate that these methods will be useful for cross-study synthesis of stability data, extrapolating measurements to unobserved scales, and identifying underlying causes and consequences of heterogeneity.
14.	De Laender, Frederik, et al. (författare) Mean species responses predict effects of environmental change on coexistence 2023 Ingår i: Ecology Letters. - : WILEY. - 1461-023X .- 1461-0248. ; 26:9, s. 1535-1547 Tidskriftsartikel (refereegranskat)abstract Environmental change research is plagued by the curse of dimensionality: the number of communities at risk and the number of environmental drivers are both large. This raises the pressing question if a general understanding of ecological effects is achievable. Here, we show evidence that this is indeed possible. Using theoretical and simulation-based evidence for bi- and tritrophic communities, we show that environmental change effects on coexistence are proportional to mean species responses and depend on how trophic levels on average interact prior to environmental change. We then benchmark our findings using relevant cases of environmental change, showing that means of temperature optima and of species sensitivities to pollution predict concomitant effects on coexistence. Finally, we demonstrate how to apply our theory to the analysis of field data, finding support for effects of land use change on coexistence in natural invertebrate communities.
15.	Guo, Guanming, et al. (författare) Towards a mechanistic understanding of variation in aquatic food chain length 2023 Ingår i: Ecology Letters. - : WILEY. - 1461-023X .- 1461-0248. ; 26:11, s. 1926-1939 Tidskriftsartikel (refereegranskat)abstract Ecologists have long sought to understand variation in food chain length (FCL) among natural ecosystems. Various drivers of FCL, including ecosystem size, resource productivity and disturbance, have been hypothesised. However, when results are aggregated across existing empirical studies from aquatic ecosystems, we observe mixed FCL responses to these drivers. To understand this variability, we develop a unified competition-colonisation framework for complex food webs incorporating all of these drivers. With competition-colonisation tradeoffs among basal species, our model predicts that increasing ecosystem size generally results in a monotonic increase in FCL, while FCL displays non-linear, oscillatory responses to resource productivity or disturbance in large ecosystems featuring little disturbance or high productivity. Interestingly, such complex responses mirror patterns in empirical data. Therefore, this study offers a novel mechanistic explanation for observed variations in aquatic FCL driven by multiple environmental factors.
16.	Haeussler, Johanna, et al. (författare) A Bayesian network approach to trophic metacommunities shows that habitat loss accelerates top species extinctions 2020 Ingår i: Ecology Letters. - : WILEY. - 1461-023X .- 1461-0248. ; 23, s. 1849-1861 Tidskriftsartikel (refereegranskat)abstract We develop a novel approach to analyse trophic metacommunities, which allows us to explore how progressive habitat loss affects food webs. Our method combines classic metapopulation models on fragmented landscapes with a Bayesian network representation of trophic interactions for calculating local extinction rates. This means that we can repurpose known results from classic metapopulation theory for trophic metacommunities, such as ranking the habitat patches of the landscape with respect to their importance to the persistence of the metacommunity as a whole. We use this to study the effects of habitat loss, both on model communities and the plant-mammal Serengeti food web dataset as a case study. Combining straightforward parameterisability with computational efficiency, our method permits the analysis of species-rich food webs over large landscapes, with hundreds or even thousands of species and habitat patches, while still retaining much of the flexibility of explicit dynamical models.
17.	Hallett, Lauren M., et al. (författare) Restoration ecology through the lens of 2023 Ingår i: Trends in Ecology & Evolution. - : CELL PRESS. - 0169-5347 .- 1872-8383. ; 38:11, s. 1085-1096 Forskningsöversikt (refereegranskat)abstract Advances in restoration ecology are needed to guide ecological restoration in a variable and changing world. Coexistence theory provides a framework for how variability in environmental conditions and species interactions affects species success. Here, we conceptually link coexistence theory and restoration ecology. First, including low-density growth rates (LDGRs), a classic metric of coexistence, can improve abundance-based restoration goals, because abundances are sensitive to initial treatments and ongoing variability. Second, growth-rate partitioning, developed to identify coexistence mechanisms, can improve restoration practice by informing site selection and indicating necessary interventions (e.g., site amelioration or competitor removal). Finally, coexistence methods can improve restoration assessment, because initial growth rates indicate trajectories, average growth rates measure success, and growth partitioning highlights interventions needed in future.
18.	Heurlin, Jasmine, et al. (författare) Behavioural synchronisation between different groups of dogs and wolves and their owners/handlers: Exploring the effect of breed and human interaction 2024 Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 19:5 Tidskriftsartikel (refereegranskat)abstract Dogs have previously been shown to synchronise their behaviour with their owner and the aim of this study was to test the effect of immediate interactions, breed, and the effects of domestication. The behavioural synchronisation test was conducted in outdoor enclosures and consisted of 30 s where the owner/handler was walking and 30 s of standing still. Three studies were conducted to explore the effect of immediate interaction (study A), the effect of breed group (study B), and the effect of domestication (study C). In study A, a group of twenty companion dogs of various breeds were tested after three different human interaction treatments: Ignore, Pet, and Play. The results showed that dogs adjusted their movement pattern to align with their owner's actions regardless of treatment. Furthermore, exploration, eye contact, and movement were all influenced by the owners moving pattern, and exploration also decreased after the Play treatment. In study B, the synchronisation test was performed after the Ignore treatment on three groups: 24 dogs of ancient dog breeds, 17 solitary hunting dogs, and 20 companion dogs (data from study A). Irrespective of the group, all dogs synchronised their moving behaviour with their owner. In addition, human walking positively influenced eye contact behaviour while simultaneously decreasing exploration behaviour. In study C, a group of six socialised pack-living wolves and six similarly socialised pack-living dogs were tested after the Ignore treatment. Interestingly, these animals did not alter their moving behaviour in response to their handler. In conclusion, dogs living together with humans synchronise with their owner's moving behaviour, while wolves and dogs living in packs do not. Hence, the degree of interspecies behavioural synchronisation may be influenced by the extent to which the dogs are immersed in everyday life with humans.
19.	Kozlov, Vladimir, et al. (författare) Biomass and biodiversity in species-rich tritrophic communities 2020 Ingår i: Ecological Complexity. - : ELSEVIER. - 1476-945X .- 1476-9840. ; 43 Tidskriftsartikel (refereegranskat)abstract We consider a tritrophic system with one basal and one top species and a large number of primary consumers, and derive upper and lower bounds for the total biomass of the middle trophic level. These estimates do not depend on dynamical regime, holding for fixed point, periodic, or chaotic dynamics. We have two kinds of estimates, depending on whether the predator abundance is zero. All these results are uniform in a self-limitation parameter, which regulates prey diversity in the system. For strong self-limitation, diversity is large; for weak self-limitation, it is small. Diversity depends on the variance of species parameter values. The larger this variance, the lower the diversity, and vice versa. Moreover, variation in the parameters of the Holling type II functional response changes the bifurcation character, with the equilibrium state with nonzero predator abundance losing stability. If that variation is small then the bifurcation can lead to oscillations (the Hopf bifurcation). Under certain conditions, there exists a supercritical Hopf bifurcation. We then find a connection between diversity and Hopf bifurcations. We also show that the system exhibits top-down regulation and a hump-shaped diversity-productivity curve. We then extend the model by allowing species to experience self-regulation. For this extended model, explicit estimates of prey diversity are obtained. We study the dynamics of this system and find the following. First, diversity and system dynamics crucially depend on variation in species parameters. We show that under certain conditions, the system undergoes a supercritical Hopf bifurcation. We also establish a connection between diversity and Hopf bifurcations. For strong self-limitation, diversity is large and complex dynamics are absent. For weak self-limitation, diversity is small and the equilibrium with non-zero predator abundance is unstable.
20.	Liao, Jinbao, et al. (författare) Competition-colonization dynamics and multimodality in diversity-disturbance relationships 2022 Ingår i: Ecology. - : WILEY. - 0012-9658 .- 1939-9170. ; 103:5 Tidskriftsartikel (refereegranskat)abstract Disturbance has long been recognized as a critical driver of species diversity in community ecology. Recently, it has been found that the well-known intermediate disturbance hypothesis, which predicts a unimodal diversity-disturbance relationship (DDR), fails to describe numerous experimental observations, as empirical DDRs are diverse. Consequently, the precise form of the DDR remains a topic of debate. Here we develop a simple yet comprehensive metacommunity framework that can account for complex competition patterns. Using both numerical simulations and analytical arguments, we show that strongly multimodal DDRs arise naturally, and this multimodality is quite robust to changing parameters or relaxing the assumption of a strict competitive hierarchy. Having multimodality as a robust property of DDRs in competition models suggests that much of the noise observed in empirical DDRs could be a critical signature of the underlying competitive dynamics.
21.	Ohlsson, Mikael, 1983- (författare) The significance of species groups for food web structure and functioning 2023 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract In ecosystems across the world, species co-exist, compete, and consume, all while adapting to environmental conditions and disruptions. An important key to the puzzle of understanding how species will respond to changes in the ecosystems, caused by for example climate change, pollution, habitat destruction, and overexploitation, is what current roles species have in a larger context. Species interactions are the basis for many ecological processes, for example, describing who eats whom in food webs. Finding groups of species that have similar interactions can provide insight into what roles species have in a food web, as well as identify core structures and functions of said food webs. Food webs are often based on data aggregates of large areas. Consequently, there is a possibility of blurring local aspects of the food web structure, thus blurring locally realized species roles. In Paper I, I used the group model to analyze local and regional group structures of a food web in the Barents Sea. The group model identiﬁes groups linked to their niche, in which species eat, and are eaten by similar species. I found the large, regional food web diverged from the local group structures, indicating that locally scaled food webs may be required to ﬁnd more accurately realized species roles. On a local scale, similar group structures were generally spatially clustered and environmentally similar. This was to some extent explained by similarities in species compositions, but more ﬁne-grained patterns related to species identities further impacted the group structures. In essence, the group model is a type of community detection based on stochastic block models. Generated groups contain groups of species with similar sets of prey and predators. Groups are related to both trophic similarity and modularity, but the process itself is, as the name implies, stochastic. Various methodologies to determine a "best ﬁt" group structure out of multiple iterations exist. Arguments can however be made, that discarded, alternative group structures may still hold ecological relevance. In Paper II, I investigated ﬁve food webs by creating a solution landscape from their respective alternative group structures. My results showed, that the core group structure remained intact across alternative solutions, while potential changes in the group structure were generally limited to smaller subsets of groups or species. Expanding on the analysis of Paper II, Paper III, accounts for the inherent un-certainty of interactions in food webs. Food webs are based on data sets, potentially covering hundreds of species and thousands of interactions. How-ever, spatial and temporal aspects, and the dynamical nature of whether interactions are realized, can impact the food web structure. Here, I investigated how group structures responded to disturbing interactions (i.e., random removal of different fractions). The key ﬁndings showed how in general, core group structures remained intact, and already unstable groups turned increasingly unstable. Species traits distinctly deﬁned group identities, but I found no particular species traits ubiquitously linked to unstable group structures. How species interact is intrinsic to their traits; basic trait-matching constraints must be fulﬁlled for an interaction to be realized, such as a predator being large enough to eat a speciﬁc prey. Traits are however also subject to change, with potentially strong selective pressures from for example environmental change or overexploitation. If traits change sufﬁciently, species interactions can also change, potentially putting affected species in a new ecological context with new predators, prey, and competitive relationships. Possibly related, the cod population in the Baltic Sea, has failed to recover even after ceasing ﬁshing. In Paper IV, I formulated an eco-evolutionary model, which considered cod’s changed ecological role after the collapse, highlighting how competition with ﬂounder species can contribute to blocking the cod population in the Baltic Sea from recovering. With this thesis, I aimed to improve understanding of how species groups based on interactions relate to food web structure. My results highlight how the group model can generate robust groups, which are generally resilient to even moderate disturbances while providing a coarse-grained representation of species roles in a food web. The spatial context of the food web, with its included species and interactions, needs to be considered to get a more accurate representation of locally realized species roles. I have further modeled how species traits may be altered by eco-evolutionary dynamics under strong selective pressure, with subsequent shifts in ecological roles. These aspects are pivotal in understanding how species in our ecosystems will be affected by today’s multitude of environmental impacts.
22.	Olusoji, Oluwafemi D., et al. (författare) Measuring individual-level trait diversity: a critical assessment of methods 2023 Ingår i: Oikos. - : WILEY. - 0030-1299 .- 1600-0706. ; 2023:4 Tidskriftsartikel (refereegranskat)abstract Individual-level trait diversity has been identified as an essential component of trait diversity (TD), influencing community assembly and structure. Traditionally, one employs trait diversity indices to measure facets of individual-level trait diversity (divergence, richness and evenness). However, the application of species-level trait diversity indices to individual-level traits data and their implications have not been adequately studied. Thus, we examined the possible challenges of using four commonly used multi-trait TD indices: Raos quadratic entropy (Rao), functional dispersion (FDis), functional evenness (FEve) and functional richness (FRic); two indices primarily developed to measure individual-level trait diversity: trait evenness distribution (TED-for evenness) and trait onion peeling (TOP-for richnness); and a modified version of TED (TEDM-for evenness). Additionally, we considered an index that integrates both evenness and richness by generalizing ordinary Hill indices for traits (coined HIT). We measured individual-level trait diversity with these indices using simulated traits data and experimental data from a growth experiment with cyanobacteria. Comparing the observed trends from the indices with the expected trends, we observed that only the trait divergence indices (FDis and Rao) produced the expected trends in the simulation scenarios and experimental data. TED and TEDM are not robust against the number of individuals used, and FEve is not sensitive to some changes in the location of individuals in the trait space. Also, TOP proved to be a discontinuous function dependent on the number of individuals, and FRic did not produce the anticipated trend when changes in the trait space did not affect the edges of the trait space. HIT did produce the anticipated changes, but it was only reliable when many individuals were sampled. In summary, applying these individual-level trait diversity indices to quantify anything except trait divergence may lead to misinterpretation of the original situation of trait distribution in the trait space if their specific properties are not adequately considered.
23.	Pastore, Abigail I., et al. (författare) The evolution of niche overlap and competitive differences 2021 Ingår i: Nature Ecology & Evolution. - : NATURE RESEARCH. - 2397-334X. ; 5:3, s. 330-337 Tidskriftsartikel (refereegranskat)abstract Competition can result in evolutionary changes to coexistence between competitors but there are no theoretical models that predict how the components of coexistence change during this eco-evolutionary process. Here we study the evolution of the coexistence components, niche overlap and competitive differences, in a two-species eco-evolutionary model based on consumer-resource interactions and quantitative genetic inheritance. Species evolve along a one-dimensional trait axis that allows for changes in both niche position and species intrinsic growth rates. There are three main results. First, the breadth of the environment has a strong effect on the dynamics, with broader environments leading to reduced niche overlap and enhanced coexistence. Second, coexistence often involves a reduction in niche overlap while competitive differences stay relatively constant or vice versa; in general changes in competitive differences maintain coexistence only when niche overlap remains constant. Large simultaneous changes in niche overlap and competitive difference often result in one of the species being excluded. Third, provided that the species evolve to a state where they coexist, the final niche overlap and competitive difference values are independent of the systems initial state, although they do depend on the models parameters. The model suggests that evolution is often a destructive force for coexistence due to evolutionary changes in competitive differences, a finding that expands the paradox of diversity maintenance. A two-species eco-evolutionary model based on consumer-resource interactions and quantitative genetic inheritance shows how evolution among competitors changes the components of stable coexistence.
24.	Pasztor, Liz, et al. (författare) Competitive Exclusion and Evolution: Convergence Almost Never Produces Ecologically Equivalent Species 2020 Ingår i: American Naturalist. - : UNIV CHICAGO PRESS. - 0003-0147 .- 1537-5323. ; 195:4, s. E112-E117 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract In a recent modeling study ("Limiting Similarity? The Ecological Dynamics of Natural Selection among Resources and Consumers Caused by Both Apparent and Resource Competition") that appeared in the April 2019 issue of The American Naturalist, Mark A. McPeek argued that ecologically equivalent species may emerge via competition-induced trait convergence, in conflict with naive expectations based on the limiting similarity principle. Although the emphasis on the possibility of the convergence of competitors is very timely, here we show that the proposed mechanism will only lead to actual coexistence in the converged state for specially chosen fine-tuned parameter settings. It is therefore not a robust mechanism for the evolution of ecologically equivalent species. We conclude that invoking trait convergence as an explanation for the co-occurrence of seemingly fully equivalent species in nature would be premature.
25.	Rael, Rosalyn C., et al. (författare) Emergent niche structuring leads to increased differences from neutrality in species abundance distributions 2018 Ingår i: Ecology. - : WILEY. - 0012-9658 .- 1939-9170. ; 99:7, s. 1633-1643 Tidskriftsartikel (refereegranskat)abstract Species abundance distributions must reflect the dynamic processes involved in community assembly, but whether and when specific processes lead to distinguishable signals is not well understood. Biodiversity and species abundances may be shaped by a variety of influences, but particular attention has been paid to competition, which can involve neutral dynamics, where competitor abundances are governed only by demographic stochasticity and immigration, and dynamics driven by trait differences that enable stable coexistence through the formation of niches. Key recent studies of the species abundance patterns of communities with niches employ simple models with pre-imposed niche structure. These studies suggest that species abundance distributions are insensitive to the relative contributions of niche and neutral processes, especially when diversity is much higher than the number of niches. Here we analyze results from a stochastic population model with competition driven by trait differences. With this model, niche structure emerges as clumps of species that persist along the trait axis, and leads to more substantial differences from neutral species abundance distributions than have been previously shown. We show that heterogeneity in between-niche interaction strength (i.e., in the strength of competition between species in different niches) plays the dominant role in shaping the species abundances along the trait axis, acting as a biotic filter favoring species at the centers of niches. Furthermore, we show that heterogeneity in within-niche interactions (i.e., in the competition between species in the same niche) counteracts the influence of heterogeneity in between-niche interactions on the SAD to some degree. Our results suggest that competitive interactions that produce niches can also influence the shapes of SADs.
26.	Rossberg, Axel G., et al. (författare) How Carefully Executed Network Theory Informs Invasion Ecology 2019 Ingår i: Trends in Ecology & Evolution. - : ELSEVIER SCIENCE LONDON. - 0169-5347 .- 1872-8383. ; 34:5, s. 385-386 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract n/a
27.	Rossberg, Axel G., et al. (författare) Lets Train More Theoretical Ecologists - Here Is Why 2019 Ingår i: Trends in Ecology & Evolution. - : ELSEVIER SCIENCE LONDON. - 0169-5347 .- 1872-8383. ; 34:9, s. 759-762 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract A tangled web of vicious circles, driven by cultural issues, has prevented ecology from growing strong theoretical roots. Now this hinders development of effective conservation policies. To overcome these barriers in view of urgent societal needs, we propose a global network of postgraduate theoretical training programs.
28.	Song, Chuliang, et al. (författare) On the Consequences of the Interdependence of Stabilizing and Equalizing Mechanisms 2019 Ingår i: American Naturalist. - : UNIV CHICAGO PRESS. - 0003-0147 .- 1537-5323. ; 194:5, s. 627-639 Tidskriftsartikel (refereegranskat)abstract We present an overlooked but important property of modern coexistence theory (MCT), along with two key new results and their consequences. The overlooked property is that stabilizing mechanisms (increasing species niche differences) and equalizing mechanisms (reducing species fitness differences) have two distinct sets of meanings within MCT: one in a two-species context and another in a general multispecies context. We demonstrate that the two-species framework is not a special case of the multispecies one, and therefore these two parallel frameworks must be studied independently. Our first result is that, using the two-species framework and mechanistic consumer-resource models, stabilizing and equalizing mechanisms exhibit complex interdependence, such that changing one will simultaneously change the other. Furthermore, the nature and direction of this simultaneous change sensitively depend on model parameters. The second result states that while MCT is often seen as bridging niche and neutral modes of coexistence by building a niche-neutrality continuum, the interdependence between stabilizing and equalizing mechanisms acts to break this continuum under almost any biologically relevant circumstance. We conclude that the complex entanglement of stabilizing and equalizing terms makes their impact on coexistence difficult to understand, but by seeing them as aggregated effects (rather than underlying causes) of coexistence, we may increase our understanding of ecological dynamics.
29.	Weiss-Lehman, Christopher P., et al. (författare) Disentangling key species interactions in diverse and heterogeneous communities : A Bayesian sparse modelling approach 2022 Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 25:5, s. 1263-1276 Tidskriftsartikel (refereegranskat)abstract Modelling species interactions in diverse communities traditionally requires a prohibitively large number of species-interaction coefficients, especially when considering environmental dependence of parameters. We implemented Bayesian variable selection via sparsity-inducing priors on non-linear species abundance models to determine which species interactions should be retained and which can be represented as an average heterospecific interaction term, reducing the number of model parameters. We evaluated model performance using simulated communities, computing out-of-sample predictive accuracy and parameter recovery across different input sample sizes. We applied our method to a diverse empirical community, allowing us to disentangle the direct role of environmental gradients on species intrinsic growth rates from indirect effects via competitive interactions. We also identified a few neighbouring species from the diverse community that had non-generic interactions with our focal species. This sparse modelling approach facilitates exploration of species interactions in diverse communities while maintaining a manageable number of parameters.
30.	Zhang, Helin, et al. (författare) Complex nonmonotonic responses of biodiversity to habitat destruction 2023 Ingår i: Ecology. - : WILEY. - 0012-9658 .- 1939-9170. ; 104:12 Tidskriftsartikel (refereegranskat)abstract It has typically been assumed that habitat destruction, characterized by habitat loss and fragmentation, has consistently negative effects on biodiversity. While numerous empirical studies have shown the detrimental effects of habitat loss, debate continues as to whether habitat fragmentation has universally negative effects. To explore the effects of habitat fragmentation, we developed a simple model for site-occupancy dynamics in fragmented landscapes. With the model, we demonstrate that a competition-colonization trade-off can result in nonlinear oscillatory responses in biodiversity to both habitat loss and fragmentation. However, the overall pattern of habitat loss reducing species richness is still established, in line with empirical observations. Interestingly, the existence of localized oscillations in biodiversity can explain the mixed responses of species richness to habitat fragmentation per se observed in nature, thereby reconciling the debate on the fragmentation-diversity relationship. Therefore, this study offers a parsimonious mechanistic explanation for empirically observed biodiversity patterns in response to habitat destruction.
31.	Zhang, Helin, et al. (författare) Dispersal network heterogeneity promotes species coexistence in hierarchical competitive communities 2021 Ingår i: Ecology Letters. - : WILEY. - 1461-023X .- 1461-0248. ; 24:1, s. 50-59 Tidskriftsartikel (refereegranskat)abstract Understanding the mechanisms of biodiversity maintenance is a fundamental issue in ecology. The possibility that species disperse within the landscape along differing paths presents a relatively unexplored mechanism by which diversity could emerge. By embedding a classical metapopulation model within a network framework, we explore how access to different dispersal networks can promote species coexistence. While it is clear that species with the same demography cannot coexist stably on shared dispersal networks, we find that coexistence is possible on unshared networks, as species can surprisingly form self-organised clusters of occupied patches with the most connected patches at the core. Furthermore, a unimodal biodiversity response to an increase in species colonisation rates or average patch connectivity emerges in unshared networks. Increasing network size also increases species richness monotonically, producing characteristic species-area curves. This suggests that, in contrast to previous predictions, many more species can co-occur than the number of limiting resources.
32.	Åkesson, Anna, 1985- (författare) Disturbances in food webs : Importance of species interactions from an ecological and evolutionary perspective 2022 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Biodiversity loss is occurring globally at an unprecedented pace. This is not only followed by ethical concerns; it also affects all levels of an ecosystem, with wide-spread implications for ecosystem functioning, services and human well-being. The severe extinction risk for many species is a result of human activities, such as habitat destruction and land-use change, overexploitation and introduction of invasive species. During the past decades, climate change has additionally become an important human-induced driver, causing biodiversity loss and altered species interactions.To mitigate the negative impact on ecosystems, we need to understand how the species building up the systems respond to disturbances. Several structural properties, both at species- and network-level, are known to affect species vulnerability. At the species-level, a species position in the food web, as well as its distribution of prey items, are important factors. At the network-level, diversity and structure of feeding interactions are important measurements related to stability. Additionally, species may both directly and indirectly affect other species, as species are entangled in complex network structures. The loss of a single species could set in motion a cascade of secondary extinctions that may not be predictable based on species’ performance in isolation. Particularly, disturbances of primary producers have a high risk to propagate and augment through the network. Moreover, species interactions have the potential to affect several other ecological processes. For example, altered environmental conditions force species to disperse to more suitable habitats, or to stay and adapt to the new local condition. Such processes can be significantly altered by species interactions. Another example concerns ecosystem service provisioning. Even if a species not being a service provider goes extinct, the event can via direct and indirect effects cause secondary extinctions of service providing species, causing loss of the services.Despite the recognition of the importance of a network context and of species interactions, such aspects are in many cases modeled in a simplified manner or not considered. In this thesis, I use mathematical models to study how species embedded in an ecological network respond to disturbances. I have two primary focus areas. First, I analyze how the interplay between evolution, dispersal and species interactions affect how species respond to climatic change. In paper I, I studied the effects of these eco-evolutionary processes under increasing temperatures, using empirically-motivated parameterizations of a suite of community models with increasing ecological interaction complexity. Second, I analyze how several structural properties affect species persistence following a disturbance. In Paper II, I focus on how network-level properties as well as species-level properties affect consumer species persistence following basal level disturbances. In Paper III, I disentangle the most influential characteristics of groups of basal species, causing a negative impact on consumer species when disturbed. I use the Serengeti savanna food web as case study. In Paper IV, I connect ecosystem services to the species providing them, and analyze how ecosystem service provisioning is affected by anthropogenic threats. I use the Baltic Sea as a case study.In summary, the results of this thesis underscore the importance of studying disturbances within a network context. Species interactions highly influenced the eco-evolutionary dynamics in Paper I, and mitigated some of the negative impacts following climatic change. Several structural network properties, both of the species being disturbed and of the species being affected, influenced species’ vulnerability following disturbance in Paper II-IV. The interplay between species influenced how disturbances percolated through the network. Moreover, Paper IV found that indirect effects mediated by the network of species interactions were of substantial importance for how anthropogenic threats are affecting ecosystem service delivery. in this thesis, I have developed novel methods, as well as extended and showcased new applications for existing ones. As such, this thesis has a broad applicability and expands our basic understanding of the interplay between ecological and evolutionary processes, as well as our understanding of the mechanisms behind how networks of interacting species are affected by disturbances. Further, the results have important implications for conservation efforts.
33.	Åkesson, Anna, et al. (författare) The importance of species interactions in eco-evolutionary community dynamics under climate change 2021 Ingår i: Nature Communications. - : Nature Portfolio. - 2041-1723. ; 12:1 Tidskriftsartikel (refereegranskat)abstract Eco-evolutionary dynamics are essential in shaping the biological response of communities to ongoing climate change. Here we develop a spatially explicit eco-evolutionary framework which features more detailed species interactions, integrating evolution and dispersal. We include species interactions within and between trophic levels, and additionally, we incorporate the feature that species interspecific competition might change due to increasing temperatures and affect the impact of climate change on ecological communities. Our modeling framework captures previously reported ecological responses to climate change, and also reveals two key results. First, interactions between trophic levels as well as temperature-dependent competition within a trophic level mitigate the negative impact of climate change on biodiversity, emphasizing the importance of understanding biotic interactions in shaping climate change impact. Second, our trait-based perspective reveals a strong positive relationship between the within-community variation in preferred temperatures and the capacity to respond to climate change. Temperature-dependent competition consistently results both in higher trait variation and more responsive communities to altered climatic conditions. Our study demonstrates the importance of species interactions in an eco-evolutionary setting, further expanding our knowledge of the interplay between ecological and evolutionary processes. Understanding the dynamics of species interactions can help predict community responses to climate change. A spatially explicit model finds that species interactions and competition mitigate the harmful impacts of climate change, and that temperature-dependent competition makes communities more variable and responsive to changing climates.

Skapa referenser, mejla, bekava och länka

Länka till träfflistan

Träfflista för sökning "WFRF:(Barabas György) "

Avgränsa träffmängd

År