scholarly journals Effect of Localization on the Stability of Mutualistic Ecological Networks

2015 ◽  
Author(s):  
Samir Suweis ◽  
Jacopo Grilli ◽  
Jayanth Banavar ◽  
Stefano Allesina ◽  
Amos Maritan
Keyword(s):  
Species Abundance ◽  
Interaction Network ◽  
Species Interaction ◽  
Interaction Networks ◽  
Ecological Communities ◽  
Weighted Degree ◽  
Perturbation Propagation ◽  
The Stability ◽  
The Impact ◽  
The Relationship

The relationships between the core-periphery architecture of the species interaction network and the mechanisms ensuring the stability in mutualistic ecological communities are still unclear. In particular, most studies have focused their attention on asymptotic resilience or persistence, neglecting how perturbations propagate through the system. Here we develop a theoretical framework to evaluate the relationship between architecture of the interaction networks and the impact of perturbations by studying localization, a measure describing the ability of the perturbation to propagate through the network. We show that mutualistic ecological communities are localized, and localization reduces perturbation propagation and attenuates its impact on species abundance. Localization depends on the topology of the interaction networks, and it positively correlates with the variance of the weighted degree distribution, a signature of the network topological hetereogenity. Our results provide a different perspective on the interplay between the architecture of interaction networks in mutualistic communities and their stability.

scholarly journals Dynamic population stage structure due to juvenile–adult asymmetry stabilizes complex ecological communities

2021 ◽  
Vol 118 (21) ◽  
pp. e2023709118
Author(s):  
André M. de Roos
Keyword(s):  
Self Regulation ◽  
Interaction Network ◽  
Population Level ◽  
Stage Structure ◽  
Current Theory ◽  
Species Interaction ◽  
Interaction Matrix ◽  
Foraging Efficiency ◽  
Ecological Communities ◽  
The Stability

Natural ecological communities are diverse, complex, and often surprisingly stable, but the mechanisms underlying their stability remain a theoretical enigma. Interactions such as competition and predation presumably structure communities, yet theory predicts that complex communities are stable only when species growth rates are mostly limited by intraspecific self-regulation rather than by interactions with resources, competitors, and predators. Current theory, however, considers only the network topology of population-level interactions between species and ignores within-population differences, such as between juvenile and adult individuals. Here, using model simulations and analysis, I show that including commonly observed differences in vulnerability to predation and foraging efficiency between juvenile and adult individuals results in up to 10 times larger, more complex communities than observed in simulations without population stage structure. These diverse communities are stable or fluctuate with limited amplitude, although in the model only a single basal species is self-regulated, and the population-level interaction network is highly connected. Analysis of the species interaction matrix predicts the simulated communities to be unstable but for the interaction with the population-structure subsystem, which completely cancels out these instabilities through dynamic changes in population stage structure. Common differences between juveniles and adults and fluctuations in their relative abundance may hence have a decisive influence on the stability of complex natural communities and their vulnerability when environmental conditions change. To explain community persistence, it may not be sufficient to consider only the network of interactions between the constituting species.

scholarly journals Vulnerable species interactions are important for the stability of mutualistic networks

2019 ◽  
Author(s):  
Benno I. Simmons ◽  
Hannah S. Wauchope ◽  
Tatsuya Amano ◽  
Lynn V. Dicks ◽  
William J. Sutherland ◽  
...  
Keyword(s):  
Species Interactions ◽  
Species Coexistence ◽  
Species Interaction ◽  
Interaction Networks ◽  
Ecological Communities ◽  
Ecological Context ◽  
Intrinsic Properties ◽  
Network Stability ◽  
Starting Point ◽  
The Stability

AbstractSpecies are central to ecology and conservation. However, it is the interactions between species that generate the functions on which ecosystems and humans depend. Despite the importance of interactions, we lack an understanding of the risk that their loss poses to ecological communities. Here, we quantify risk as a function of the vulnerability (likelihood of loss) and importance (contribution to network stability in terms of species coexistence) of 4330 mutualistic interactions from 41 empirical pollination and seed dispersal networks across six continents. Remarkably, we find that more vulnerable interactions are also more important: the interactions that contribute most to network stability are those that are most likely to be lost. Furthermore, most interactions tend to have more similar vulnerability and importance across networks than expected by chance, suggesting that vulnerability and importance may be intrinsic properties of interactions, rather than only a function of ecological context. These results provide a starting point for prioritising interactions for conservation in species interaction networks and, in areas lacking network data, could allow interaction properties to be inferred from taxonomy alone.

scholarly journals Real-world Interaction Networks Buffer Impact of Small Evolutionary Shifts On Biodiversity

2014 ◽  
Author(s):  
Gabriel E Leventhal ◽  
Liyu Wang ◽  
Roger D Kouyos
Keyword(s):  
Real World ◽  
Environmental Changes ◽  
Interaction Network ◽  
Species Interaction ◽  
Interaction Networks ◽  
Community Diversity ◽  
Ecological Communities ◽  
Interaction Structure ◽  
Evolutionary Changes ◽  
Biodiversity Maintenance

Biodiversity maintenance and community evolution depend on the species interaction network. The "diversity-stability debate" has revealed that the complex interaction structure within real-world ecosystems determines how ecological communities respond to environmental changes, but can have opposite effects depending on the community type. Here we quantify the influence of shifts on community diversity and stability at both the species level and the community level. We use interaction networks from 19 real-world mutualistic communities and simulate shifts to antagonism. We demonstrate that both the placement of the shifting species in the community, as well as the structure of the interaction network as a whole contribute to stability and diversity maintenance under shifts. Our results suggest that the interaction structure of natural communities generally enhances community robustness against small ecological and evolutionary changes, but exacerbates the consequences of large changes.

scholarly journals Political Instability and Growth: Case of the Developing Countries

2013 ◽  
Vol 2 (1) ◽  
pp. 19
Author(s):  
Said JAOUADI ◽  
Lamia ARFAOUI ◽  
Azza ZIEDI
Keyword(s):  
Developing Countries ◽  
Empirical Investigation ◽  
Political Instability ◽  
Political Environment ◽  
Huge Number ◽  
Effective Governance ◽  
The Social ◽  
The Stability ◽  
The Impact ◽  
The Relationship

The paper attempted to examine the causal relationship between political instability and growth. Currently, the world continues to record huge number of popular revolutions in the region MENA, to improve the social environment and to consolidate implementing an effective governance. Although, the uprising has harmed the financial and economic situation in these countries, and became a threat for the stability of the countries, in overall.The manuscript accounts for the impact of political instability on the growth of the developing countries, in the shadow of the widespread of the revolutions since 2011. The paper attempted to illuminate the reality of the relationship between political environment and growth through the estimation of panel, comprising 69 developing countries 1985-2012.In the current paper, the authors conducted an empirical investigation, in which we bore out the claims raised in many surveys and the conclusions drawn by several authors about the harmful impact of political instability on the fundamental bases of the economy, in countries recording political instability.

scholarly journals Do alternative weighting approaches for an Index of Multiple Deprivation change the association with mortality? A sensitivity analysis from Germany

BMJ Open ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. e028553 ◽  
Author(s):  
Florian Schederecker ◽  
Christoph Kurz ◽  
Jon Fairburn ◽  
Werner Maier
Keyword(s):  
Age Groups ◽  
Total Mortality ◽  
Premature Mortality ◽  
Area Deprivation ◽  
Multiple Deprivation ◽  
The Stability ◽  
Weighting Procedures ◽  
The Impact ◽  
The Relationship ◽  
Index Of Multiple Deprivation

ObjectivesThis study aimed to assess the impact of using different weighting procedures for the German Index of Multiple Deprivation (GIMD) investigating their link to mortality rates.Design and settingIn addition to the original (normative) weighting of the GIMD domains, four alternative weighting approaches were applied: equal weighting, linear regression, maximization algorithm and factor analysis. Correlation analyses to quantify the association between the differently weighted GIMD versions and mortality based on district-level official data from Germany in 2010 were applied (n=412 districts).Outcome measuresTotal mortality (all age groups) and premature mortality (<65 years).ResultsAll correlations of the GIMD versions with both total and premature mortality were highly significant (p<0.001). The comparison of these associations using Williams’s t-test for paired correlations showed significant differences, which proved to be small in respect to absolute values of Spearman’s rho (total mortality: between 0.535 and 0.615; premature mortality: between 0.699 and 0.832).ConclusionsThe association between area deprivation and mortality proved to be stable, regardless of different weighting of the GIMD domains. The theory-based weighting of the GIMD should be maintained, due to the stability of the GIMD scores and the relationship to mortality.

scholarly journals Genetics-based interactions of foundation species affect community diversity, stability and network structure

2017 ◽  
Vol 284 (1854) ◽  
pp. 20162703 ◽  
Author(s):  
Arthur R. Keith ◽  
Joseph K. Bailey ◽  
Matthew K. Lau ◽  
Thomas G. Whitham
Keyword(s):  
Network Structure ◽  
Experimental Manipulation ◽  
Species Interaction ◽  
Foundation Species ◽  
Interaction Networks ◽  
Community Diversity ◽  
Arthropod Community ◽  
Pemphigus Betae ◽  
In The Wild ◽  
The Stability

We examined the hypothesis that genetics-based interactions between strongly interacting foundation species, the tree Populus angustifolia and the aphid Pemphigus betae , affect arthropod community diversity, stability and species interaction networks of which little is known. In a 2-year experimental manipulation of the tree and its aphid herbivore four major findings emerged: (i) the interactions of these two species determined the composition of an arthropod community of 139 species; (ii) both tree genotype and aphid presence significantly predicted community diversity; (iii) the presence of aphids on genetically susceptible trees increased the stability of arthropod communities across years; and (iv) the experimental removal of aphids affected community network structure (network degree, modularity and tree genotype contribution to modularity). These findings demonstrate that the interactions of foundation species are genetically based, which in turn significantly contributes to community diversity, stability and species interaction networks. These experiments provide an important step in understanding the evolution of Darwin's ‘entangled bank’, a metaphor that characterizes the complexity and interconnectedness of communities in the wild.

GROWTH INTENTIONS AND ACTUAL GROWTH: THE IMPACT OF ENTREPRENEURIAL CHOICE

1996 ◽  
Vol 04 (01) ◽  
pp. 1-17 ◽  
Author(s):  
LARS KOLVEREID ◽  
ERLEND BULLVAG
Keyword(s):  
Graduate School ◽  
Firm Growth ◽  
Longitudinal Design ◽  
Growth Patterns ◽  
Design Data ◽  
Actual Growth ◽  
Global Entrepreneurship ◽  
The Stability ◽  
The Impact ◽  
The Relationship

Acknowledgements: We would like to thank the Norwegian Royal Ministry of Industry and the Bodø Graduate School of Business for the financial support that made this research possible. We would also like to thank the Society of Associated Researchers in Entrepreneurship under whose auspices the data for this study was collected. An earlier version of this paper was presented at the 3rd Annual Global Entrepreneurship Conference, Lyon, France, March 1993. The present research investigated: (1) the relationship between entrepreneurs’ growth intentions and actual firm growth, (2) the stability of growth intentions, and (3) the relationship between changes in intentions and actual firm growth. Using a longitudinal design, data were collected from Norwegian entrepreneurs for 1990 and 1992. The results indicate that growth intentions may be used to predict actual growth, that past intentions are related to later intentions, and that changes in growth intentions are associated with changes in growth patterns.

scholarly journals A novel perspective on the meaning of nestedness with conceptual and methodological solutions

2021 ◽  
Author(s):  
Rafael Barros Pereira Pinheiro ◽  
Carsten F. Dormann ◽  
Gabriel Moreira Felix ◽  
Marco A. R. Mello
Keyword(s):  
Null Model ◽  
Interaction Network ◽  
Species Interaction ◽  
Null Models ◽  
Interaction Networks ◽  
Common Pattern ◽  
Expected Values ◽  
New Perspective ◽  
Test Outcomes ◽  
Plant Pollinator

Aim: Nestedness is a common pattern in metacommunities and interaction networks, whose causes are still discussed. Nestedness inference is challenging because, beyond calculating an index, we need to compare observed values with values generated with a null model. There are different null models and the choice between them affects test outcomes. Furthermore, there is no established theoretical basis to guide this choice. Here, we propose a different look at the meaning of nestedness that improves our understanding of its causes and unveils the link between null models and hypotheses. Innovation: Nestedness of a matrix is a combination of marginal sum inequality and high overlap. The higher the overlap, the more predictable the cell values by marginal sums. Here, we show that nestedness actually measures how better one can predict cell values by marginal sums than by matrix dimensions and total sum alone. From this, we propose that two null models can be used to test for different topological hypotheses. The equiprobable model excludes all nestedness-generating mechanisms and provides the distribution of expected values for nestedness significance tests. The proportional model conserves nestedness-generating mechanisms and excludes nestedness-disrupting mechanisms, and thus, produces highly nested matrices. The proportional model provides the distribution of expected nestedness for nested matrices. Additionally, we evaluate the efficiency of several indices within this new perspective and illustrate our approach using an empirical plant-pollinator network. Main conclusions: Through a shift of perspective, our approach reconciliates contradictions in null model analysis and delimits the range of possible explanations for nestedness. The only way a process can increase nestedness in a matrix is by promoting marginal sum inequalities, without concomitantly introducing preferences. Consequently, in a species interaction network, explanations for nestedness should explain why some species interact more frequently than others.

scholarly journals IRRIGATION - THE BASIS FOR INCREASING THE STABILITY OF ENTOMOCENOSES IN ARID CONDITIONS OF SOUTHEAST OF RUSSIA

2019 ◽  
Vol 14 (1) ◽  
pp. 34-39
Author(s):  
Виктор Мелихов ◽  
Viktor Melihov ◽  
Евгений Комаров ◽  
Evgeniy Komarov ◽  
Ольга Комарова ◽  
...  
Keyword(s):  
Species Abundance ◽  
Agricultural Landscapes ◽  
Physiological Indicators ◽  
Air Temperatures ◽  
Irrigated Crops ◽  
Microclimatic Conditions ◽  
The Difference ◽  
Pesticide Load ◽  
The Stability ◽  
The Relationship

The article presents materials of perennial (1988–2017) studies on solving problems of stabilizing the phytosanitary situation in irrigated agrocenoses. The paper presents the results of studying the species abundance and insects, the patterns of their change under the influence of irrigation in the Lower Volga region. The effect of irrigation on the change in environmental conditions by the parameters of productivity of agrobiocenoses and microclimate is shown. The difference in air temperature in irrigated by sprinkling and non-irrigated agrocenoses immediately after watering reaches 7-8° C. In general, during the growing season, the average daily air temperatures in the irrigated agrocenosis were 2-4° C lower, compared to the non-irrigated. More mesophytic microclimatic conditions, which are formed under the influence of irrigation, are the leading factor determining the increase in the biodiversity of the entomocomplexes of irrigated agrocenoses due to an increase in species abundance and the number of mesophilic and hygrophilic insects. An increase in species diversity and abundance of meso-and hygrophilic in irrigated agricultural landscapes due to the emergence of new micro-sites (canals, spillways, storage ponds, etc.) is also shown. The formation of irrigated conditions in poly-dominant entomological communities, which increase the balance of the agroecosystem, including by optimizing its trophic structure. The changing ecological situation in irrigated agricultural landscapes determines the cultivation of plants with optimized physiological indicators, and the biological characteristics of the development of harmful and beneficial insects change under irrigation conditions. All this directly affects the relationship between phytophages and plants, as well as their survival, fertility, life expectancy of individual phases and other biological features of populations. It is noted that on irrigated crops there is a more favorable relationship between entomophages and pests, making it possible to self-regulate the entomofauna due to increased activity of entomophages. This creates a real opportunity to save the crop and reduce the pesticide load by 40-50% on irrigated crops.

scholarly journals LifeWebs: A (global) database of bipartite ecological interaction networks

2021 ◽  
Vol 5 ◽  
Author(s):  
Philip Butterill ◽  
Leonardo Jorge ◽  
Shuang Xing ◽  
Tom Fayle
Keyword(s):  
Interaction Network ◽  
Community Level ◽  
Interaction Networks ◽  
Sampling Effort ◽  
Ecological Communities ◽  
Bipartite Networks ◽  
Data Types ◽  
User Friendliness ◽  
Global Database ◽  
Machine Readable

The structure and dynamics of ecological interactions are nowadays recognized as a crucial challenge to comprehend the assembly, functioning and maintenance of ecological communities, their processes and the services they provide. Nevertheless, while standards and databases for information on species occurrences, traits and phylogenies have been established, interaction networks have lagged behind on the development of these standards. Here, we discuss the challenges and our experiences in developing a global database of bipartite interaction networks. LifeWebs*1 is an effort to compile community-level interaction networks from both published and unpublished sources. We focus on bipartite networks that comprise one specific type of interaction between two groups of species (e.g., plants and herbivores, hosts and parasites, mammals and their microbiota), which are usually presented in a co-occurrence matrix format. However, with LifeWebs, we attempt to go beyond simple matrices by integrating relevant metadata from the studies, especially sampling effort, explicit species information (traits and taxonomy/phylogeny), and environmental/geographic information on the communities. Specifically, we explore 1) the unique aspects of community-level interaction networks when compared to data on single inter-specific interactions, occurrence data, and other biodiversity data and how to integrate these different data types. 2) The trade-off between user friendliness in data input/output vs. machine-readable formats, especially important when data contributors need to provide large amounts of data usually compiled in a non-machine-readable format. 3) How to have a single framework that is general enough to include disparate interaction types while retaining all the meaningful information. We envision LifeWebs to be in a good position to test a general standard for interaction network data, with a large variety of already compiled networks that encompass different types of interactions. We provide a framework for integration with other types of data, and formalization of the data necessary to represent networks into established biodiversity standards.

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