| 1. |
- Barabas, György, et al.
(författare)
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Self-regulation and the stability of large ecological networks
- 2017
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Ingår i: NATURE ECOLOGY and EVOLUTION. - : NATURE PUBLISHING GROUP. - 2397-334X. ; 1:12, s. 1870-
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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.
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| 2. |
- Dee, Laura E., et al.
(författare)
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Operationalizing Network Theory for Ecosystem Service Assessments
- 2017
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Ingår i: Trends in Ecology & Evolution. - : ELSEVIER SCIENCE LONDON. - 0169-5347 .- 1872-8383. ; 32:2, s. 118-130
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Forskningsöversikt (refereegranskat)abstract
- Managing ecosystems to provide ecosystem services in the face of global change is a pressing challenge for policy and science. Predicting how alternative management actions and changing future conditions will alter services is complicated by interactions among components in ecological and socioeconomic systems. Failure to understand those interactions can lead to detrimental outcomes from management decisions. Network theory that integrates ecological and socioeconomic systems may provide a path to meeting this challenge. While network theory offers promising approaches to examine ecosystem services, few studies have identified how to operationalize networks for managing and assessing diverse ecosystem services. We propose a framework for how to use networks to assess how drivers and management actions will directly and indirectly alter ecosystem services.
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| 3. |
- Grilli, Jacopo, et al.
(författare)
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Feasibility and coexistence of large ecological communities
- 2017
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- The role of species interactions in controlling the interplay between the stability of ecosystems and their biodiversity is still not well understood. The ability of ecological communities to recover after small perturbations of the species abundances (local asymptotic stability) has been well studied, whereas the likelihood of a community to persist when the conditions change (structural stability) has received much less attention. Our goal is to understand the effects of diversity, interaction strengths and ecological network structure on the volume of parameter space leading to feasible equilibria. We develop a geometrical framework to study the range of conditions necessary for feasible coexistence. We show that feasibility is determined by few quantities describing the interactions, yielding a nontrivial complexity-feasibility relationship. Analysing more than 100 empirical networks, we show that the range of coexistence conditions in mutualistic systems can be analytically predicted. Finally, we characterize the geometric shape of the feasibility domain, thereby identifying the direction of perturbations that are more likely to cause extinctions.
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| 4. |
- Grilli, Jacopo, et al.
(författare)
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Higher-order interactions stabilize dynamics in competitive network models
- 2017
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 548:7666, s. 210-
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Tidskriftsartikel (refereegranskat)abstract
- Ecologists have long sought a way to explain how the remarkable biodiversity observed in nature is maintained. On the one hand, simple models of interacting competitors cannot produce the stable persistence of very large ecological communities(1-5). On the other hand, neutral models(6-9), in which species do not interact and diversity is maintained by immigration and speciation, yield unrealistically small fluctuations in population abundance(10), and a strong positive correlation between a species' abundance and its age(11), contrary to empirical evidence. Models allowing for the robust persistence of large communities of interacting competitors are lacking. Here we show that very diverse communities could persist thanks to the stabilizing role of higher-order interactions(12,13), in which the presence of a species influences the interaction between other species. Although higher-order interactions have been studied for decades(14-16), their role in shaping ecological communities is still unclear(5). The inclusion of higher-order interactions in competitive network models stabilizes dynamics, making species coexistence robust to the perturbation of both population abundance and parameter values. We show that higher-order interactions have strong effects in models of closed ecological communities, as well as of open communities in which new species are constantly introduced. In our framework, higher-order interactions are completely defined by pairwise interactions, facilitating empirical parameterization and validation of our models.
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