Diversity–Stability Relationships in Community Ecology: Re-Examination of the Portfolio Effect

Lhomme, Jean; Winkel, Thierry

doi:10.1006/tpbi.2002.1612

Cited by 40 publications

(32 citation statements)

References 33 publications

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“…When few taxa numerically dominate the system, community stability can be driven by fluctuations of these components (Steiner et al 2005, Polley et al 2007). In addition, large differences among species abundances can result in negative and curvilinear richness-stability relationships when z = 1.2 (Lhomme & Winkel 2002). In our case, the z-values were close to 1.2 (e.g.…”

Section: Community Stabilitymentioning

confidence: 64%

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Observational evidence of a negative biodiversity–stability relationship in intertidal epibenthic communities

Valdivia¹,

Molis²

2009

Aquat. Biol.

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The idea that diversity begets the functioning and stability of ecosystems has been intensely examined in terrestrial habitats, yet these relationships remain poorly studied in the marine realm. Theoretical and empirical work suggest that diversity enhances the stability of communities, but decreases the stability of populations. This is because compensatory dynamics, such as when one species decreases while another increases, stabilise the community as long as species richness increases the variety of responses to the environment. In an observational field study, the temporal variability in species abundance was used as a measure of stability that was compared among 5 intertidal sites of naturally different species richness. Percent coverage of macrobenthic species was estimated every 6 mo for 2 yr. Stability in total community coverage was a negative but curvilinear function of species richness. In addition, the stability of single populations (averaged over all species) fluctuated across the species richness gradient, without showing the predicted negative pattern. We found no evidence for increasing compensatory dynamics with increasing species richness, suggesting that the variety of responses to environmental changes was unrelated to diversity. Diversity-stability relationships in natural communities may be more complex than those predicted by theory and manipulative experiments.

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Section: Community Stabilitymentioning

confidence: 64%

“…When species contribute unequally to the community abundance, the negative effect of diversity on community variability is dampened (Doak et al 1998), as shown in terrestrial plant communities (Polley et al 2007). Moreover, high species dominance can lead to negative and non-linear diversity-stability relationships (Lhomme & Winkel 2002).…”

Section: Introductionmentioning

confidence: 99%

Observational evidence of a negative biodiversity–stability relationship in intertidal epibenthic communities

Valdivia¹,

Molis²

2009

Aquat. Biol.

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“…Despite the popularity of the idea that many systems from natural and social sciences and technology display the portfolio effect, there are various objections regarding its claimed occurrence in some specific cases. For example, in ecology some stochastic models and sets of experimental data suggest that there are systems for which the portfolio effect does not exist (2)(3)(4)(5). The purpose of this article is to show that some systems may display an anti-portfolio effect for which the combination of different resources reduces the stability of the systems with respect to fluctuations.…”

mentioning

confidence: 99%

“…For example, it is expected that a diversified investment portfolio would provide a small, but stable, low-risk profit stream; reducing the numbers of resources opens the way for possible higher profits but at a higher risk (1). Similarly, in agriculture, increasing biodiversity, that is, using different genetic varieties of a plant, is expected to increase the stability of the harvest with respect to environmental fluctuations (2)(3)(4). For example, if only a high-yield crop that is sensitive to bad weather is cultivated, then it is likely to have either a good harvest (good weather) or none at all (bad weather).…”

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confidence: 99%

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On anti-portfolio effects in science and technology with application to reaction kinetics, chemical synthesis, and molecular biology

Vlad¹,

Corlan²,

Popa³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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The portfolio effect is the increase of the stability of a system to random fluctuations with the increase of the number of random state variables due to spreading the risk among these variables; many examples exist in various areas of science and technology. We report the existence of an opposite effect, the decrease of stability to random fluctuations due to an increase of the number of random state variables. For successive industrial or biochemical processes of independent, random efficiencies, the stability of the total efficiency decreases with the increase of the number of processes. Depending on the variables considered, the same process may display both a portfolio as well as an anti-portfolio behavior. In disordered kinetics, the activation energy of a reaction or transport process is the result of a sum of random components. Although the total activation energy displays a portfolio effect, the rate coefficient displays an anti-portfolio effect. For randomchannel kinetics, the stability of the total rate coefficient increases with the average number of reaction pathways, whereas the stability of the survival function has an opposite behavior: it decreases exponentially with the increase of the average number of reaction pathways (anti-portfolio effect). In molecular biology, the total rate of a nucleotide substitution displays a portfolio effect, whereas the probability that no substitutions occur displays an anti-portfolio effect, resulting in faster evolutionary processes due to fluctuations. The anti-portfolio effect emerges for products of random variables or equations involving multiplicative convolution products. disordered kinetics ͉ molecular biology clocks ͉ molecular evolution ͉ multiplicative random variables ͉ random fields

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Increasing stability of a native freshwater fish assemblage following flow rehabilitation

Jacinto

Fangue

Cocherell

et al. 2023

Ecological Applications

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Stream restorations are increasingly critical for managing and recovering freshwater biodiversity in human-dominated landscapes. However, few studies have quantified how rehabilitative actions promulgate through aquatic communities over decades. Here, a long-term dataset is analyzed for fish assemblage change, incorporating data pre-and post-restoration periods, and testing the extent to which native assemblage stability has increased over time. In the late 1950s, a large capacity dam was installed on Putah Creek (Solano County, CA, USA), which altered the natural flow regime, channel structure, geomorphic processes, and overall ecological function. Notably, downstream flows were reduced (especially during summer months) resulting in an aquatic assemblage dominated by warm-water nonnative species, while endemic native species subsisted at low levels as subordinates. A court-mediated Accord was ratified in 2000, providing a more natural flow regime, specifically for native and anadromous fishes in the stream. The richness of nonnative

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Diversity–Stability Relationships in Community Ecology: Re-Examination of the Portfolio Effect

Cited by 40 publications

References 33 publications

Observational evidence of a negative biodiversity–stability relationship in intertidal epibenthic communities

Observational evidence of a negative biodiversity–stability relationship in intertidal epibenthic communities

On anti-portfolio effects in science and technology with application to reaction kinetics, chemical synthesis, and molecular biology

Increasing stability of a native freshwater fish assemblage following flow rehabilitation

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