Body Sizes of Consumers and Their Resources

Understanding what structures ecological communities is vital to answering questions about extinctions, environmental change, trophic cascades, and ecosystem functioning. Optimal foraging theory was conceived to increase such understanding by providing a framework with which to predict species interactions and resulting community structure. Here, we use an optimal foraging model and allometries of foraging variables to predict the structure of real food webs. The qualitative structure of the resulting model provides a more mechanistic basis for the phenomenological rules of previous models. Quantitative analyses show that the model predicts up to 65% of the links in real food webs. The deterministic nature of the model allows analysis of the model's successes and failures in predicting particular interactions. Predacious and herbivorous feeding interactions are better predicted than pathogenic, parasitoid, and parasitic interactions. Results also indicate that accurate prediction and modeling of some food webs will require incorporating traits other than body size and diet choice models specific to different types of feeding interaction. The model results support the hypothesis that individual behavior, subject to natural selection, determines individual diets and that food web structure is the sum of these individual decisions.body size ͉ complexity ͉ connectance E xplaining and predicting community structure is a central part of ecological research. It is vital to answering questions about extinctions (1, 2), environmental change (3), trophic cascades (4), and ecosystem functioning (5, 6). We focus on one of the major components of community structure: the interactions between consumers and resources. Food webs represent communities in terms of species and the feeding links between them, and discovering what determines their structure is a major goal in ecology.There are several different approaches to modeling food webs, each emphasizing different processes by which food web structure might be controlled. For example, dynamic models focus on how structure relates to population dynamics and community stability (2, 7-11). Evolutionary models incorporate the processes that control the formation and expansion of food webs (12, 13). Static models include rules that determine structural attributes of food webs (14-19). These models have developed our thinking about food webs in a number of ways, but they have limitations. The stochastic, and therefore generalized, nature of these models means that predicting the arrangement of links in a particular real food web is difficult. Here, we describe a new approach to modeling food webs that avoids some of these problems through use of the allometries of body size and foraging behavior of individual consumers.The contingency model of optimal foraging predicts the diet that maximises a consumer's rate of energy intake (20). We have shown that this optimal foraging model can predict consumer diet breadths and food web connectance (21). This model of connectance [which we te...

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“…The estimation of the species/life-stage sizes used in analyses of real food webs is detailed in Brose et al (42).…”

Section: Methodsmentioning

confidence: 99%

Size, foraging, and food web structure

Petchey

Beckerman²,

Riede³

et al. 2008

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

495

653

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“…The food webs were extracted from the database of Brose et al (2005); specifically, we used here the networks for which the trophic interactions were determined from direct observation, as has been done by and Naisbit et al (2011Naisbit et al ( , 2012. Both the plant-frugivore and the plant-pollinator webs were extracted from the recently compiled data set of .…”

Section: Data Setsmentioning

confidence: 99%

Components of Phylogenetic Signal in Antagonistic and Mutualistic Networks

Rohr

Bascompte

2014

The American Naturalist

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Recent studies have shown a phylogenetic signal in the structure of ecological networks, making the point that evolutionary history is important in explaining network architecture. However, this previous work has focused on either antagonistic (i.e., predatorprey) or mutualistic networks and has used different methodologies. Thus, a comparative assessment of both the frequency and the strength of phylogenetic signal across network types and components of network structure has been precluded. Here, we address this issue using a data set comprising 60 antagonistic and mutualistic networks. By quantifying simultaneously the matching and centrality components of network architecture-capturing the modular and nested structure, respectively-we test the presence and quantify the strength of phylogenetic signal across network types, species sets, and components of network structure. We find contrasting differences across such groups. First, phylogenetic signal is stronger in antagonistic webs than in mutualistic webs. Second, resources are more strongly constrained than consumers in food webs, while animals show more constraints than plants in mutualistic networks. Third, phylogenetic constraints are stronger for the matching component than for the centrality component of network structure. These results can shed light on the contrasting evolutionary constraints shaping network structure across interaction types and species sets.

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“…Reported size data refer either to average body masses or average body lengths of individuals (Brose et al, 2005), so we generically use the term 'body size' to encompass both cases. For each food web we determine the empirical number of diet gaps G e derived from the body-size ordering (see Appendix A for a list of values and details about these orderings).…”

Section: Diet Contiguity Confidence Intervalsmentioning

confidence: 99%

Degree of intervality of food webs: From body-size data to models

Capitán

Arenas

Guimerà

2013

Journal of Theoretical Biology

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Diet contiguity Ecological networks Food-web structure Niche dimension Species sizeIn food webs, the degree of intervality of consumers' diets is an indicator of the number of dimensions that are necessary to determine the niche of a species. Previous studies modeling food-web structure have shown that real networks are compatible with a high degree of diet contiguity. However, current models are also compatible with the opposite, namely that species' diets have relatively low contiguity. This is particularly true when one takes species' body size as a proxy for niche value, in which case the indeterminacy of diet contiguities provided by current models can be large. We propose a model that enables us to narrow down the range of possible values of diet contiguity. According to this model, we find that diet contiguity not only can be high, but must be high when species are ranked in ascending order of body size.

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Body Sizes of Consumers and Their Resources

Cited by 115 publications

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Size, foraging, and food web structure

Size, foraging, and food web structure

Components of Phylogenetic Signal in Antagonistic and Mutualistic Networks

Degree of intervality of food webs: From body-size data to models

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