A Stochastic Theory of Community Food Webs

Cohen, Joel E.; Newman, Charles M.; Briand, Frédéric; Pałka, Zbigniew

doi:10.1007/978-3-642-83784-5_3

Cited by 41 publications

(20 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We reproduced these results with our version of the Grötschel and Wakabayashi algorithm. The optimal partition for modularity maximization contains the following 5 communities: C m 1 = {1, 2, 3,5,6,7,8,19,29, 30} with 6 n and 4 c, C m 2 = {4, 9,10,11,12,13,14,15,16,17,18,20,21,22,23,24,25,26,27,28,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,54,55,56 and 3 c. These 5 communities consist of two large ones with no (for c) or very few (for l) misclassifications, two small communities with both n and c books and one community with all three categories. We count misclassifications as follows: any l in a community with a majority of c's or n's or conversely counts for 1;…”

Section: Krebs' Political Booksmentioning

confidence: 99%

Edge ratio and community structure in networks

2010

View full text Add to dashboard Cite

Les textes publiés dans la série des rapports de recherche HEC n'engagent que la responsabilité de leurs auteurs. La publication de ces rapports de recherche bénéficie d'une subvention du Fonds québécois de la recherche sur la nature et les technologies. September 2009Les Cahiers du GERAD G-2009-55 Copyright c 2009 GERAD AbstractA new hierarchical divisive algorithm is proposed for identifying communities in complex networks. To that effect, the definition of community in the weak sense of Radicchi et al. is extended into a criterion for a bipartition to be optimal: one seeks to maximize the minimum for both classes of the bipartition of the ratio of inner edges to cut edges. A mathematical program is used within a dichotomous search to do this in an optimal way for each bipartition. This includes an exact solution of Wang et al.'s problem of detecting indivisible communities. The resulting hierarchical divisive algorithm is compared with exact modularity maximization on both artificial and real world datasets. For two problems of the former kind optimal solutions are found, for five problems of the latter kind the edge ratio algorithm always appears to be competitive. Moreover, it provides new information in several cases, notably through the use of the dendrogram summarizing the resolution. RésuméUn nouvel algorithme hiérarchique divisif est proposé pour l'identification des communautés dans les réseaux complexes. Pour ce faire, la définition de communauté au sens faible de Radicchi et al. est etendue en un critère pour qu'une bipartition soit optimale : on chercheà maximiser le minimum pour les deux classes de la bipartition du rapport du nombre d'arêtes internes au nombre d'arêtes coupées. Un programme mathématique est utiliséà l'intérieur d'une procédure de recherche dichotomique pour se faire de manière optimale pour chaque bipartition. On obtient ainsi une solution exacte au problème de Wang et al. de détecter des communautés indivisibles. L'algorithme hiérarchique divisif résultant est comparé avec la maximisation exacte de la modularité sur des ensembles de données artificielles et réelles. Pour deux problèmes de la première sorte, les solutions optimales sont obtenues et pour cinq problèmes de la seconde sorte l'algorithme proposé se montre toujours compétitif. De plus, il produit de l'information nouvelle dans plusieurs cas notamment par l'usage du dendrogramme résumant la résolution.

show abstract

Section: Krebs' Political Booksmentioning

confidence: 99%

Edge ratio and community structure in networks

2010

View full text Add to dashboard Cite

show abstract

“…We analyzed daily over two seasons (of two years) the mechanism of assembly or attachment of new species (i.e., species that initiated flowering or began active foraging) to old species already established in the network. To understand the formation of network patterns, theoreticians have developed a family of models of network buildup (Cohen and Newman 1985, Williams and Martinez 2000, Sugihara et al 2003, Cattin et al 2004. One of these models is preferential attachment .…”

Section: Introductionmentioning

confidence: 99%

Temporal Dynamics in a Pollination Network

Olesen

Bascompte

Elberling³

et al. 2008

Ecology

447

498

View full text Add to dashboard Cite

Despite a strong current interest in ecological networks, the bulk of studies are static descriptions of the structure of networks, and very few analyze their temporal dynamics. Yet, understanding network dynamics is important in order to relate network patterns to ecological processes. We studied the day-to-day dynamics of an arctic pollination interaction network over two consecutive seasons. First, we found that new species entering the network tend to interact with already well-connected species, although there are deviations from this trend due, for example, to morphological mismatching between plant and pollinator traits and nonoverlapping phenophases of plant and pollinator species. Thus, temporal dynamics provides a mechanistic explanation for previously reported network patterns such as the heterogeneous distribution of number of interactions across species. Second, we looked for the ecological properties most likely to be mediating this dynamical process and found that both abundance and phenophase length were important determinants of the number of links per species.

show abstract

“…The cascade model was proposed by Cohen and Newman (1985) as "a stochastic theory of 156 community food webs" that would explain observed food web patterns. It is a simple, but still 157 usefull null-model (Gotelli and Graves 1997) for the distribution of trophic links, without 158 detailed biological mechanisms, that results of the present analysis can be compared with.…”

mentioning

confidence: 99%

Trophic links and the relationship between predator and prey body sizes in food webs

Jönsson¹

2014

Community Ecology

View full text Add to dashboard Cite

1The relationship between predator and prey body sizes is an important property of food webs 2 with potential implications for community dynamics and ecosystem functioning. To shed 3 more light on this issue I here analyze the relationships between prey size, predator size and 4 trophic position of consumers, using body size estimates of 697 species in 52 food webs. 5First I show that the relationship between predator and prey body sizes across many 6 systems can be different from, and potentially obscure the true relationship within systems. 7More specifically, when data from all webs are aggregated average prey size is positively 8 correlated to predator size with a regression slope less than unity, suggesting that predators 9 become less similar in size to their average prey the larger the predator is, and consequently 10 that the relative size difference between a predator and its prey should increase with the 11 trophic position of the consumer. However, despite this I find the predator-prey body mass 12 ratio to be negatively correlated to the trophic position of the consumer within many webs. 13The reason for this is that the across-webs pattern is not representative for the within-web 14 relationship. 15Second, I show that the pattern observed is not compatible with a simple null-model for 16 the distribution of trophic links between predators and prey. The observed relationship 17 between predator size and mean prey size is for most webs significantly steeper than that 18 predicted by the cascade model. Furthermore, the observed relationship also deviates 19 significantly (but less so) from an ecologically more realistic model for the distribution of 20 trophic links (the niche model). 21The results contradict the traditional Eltonian paradigm that predator-prey body mass 22 ratios do not vary consistently across trophic levels. It is concluded that more studies are 23 needed to establish the generality of the results and explore its dynamical implications. 24 25 Predator-prey body size ratios in food webs 2

show abstract

A Stochastic Theory of Community Food Webs

Cited by 41 publications

References 0 publications

Edge ratio and community structure in networks

Edge ratio and community structure in networks

Temporal Dynamics in a Pollination Network

Trophic links and the relationship between predator and prey body sizes in food webs

Contact Info

Product

Resources

About