Variability in interaction strength and implications for biodiversity

Kokkoris, Giorgos D.; Jansen, Vincent; Loreau, Michel; Troumbis, Andreas Y.

doi:10.1046/j.1365-2656.2002.00604.x

Cited by 117 publications

(138 citation statements)

References 38 publications

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“…The long-tailed nature of this distribution reveals that most interactions are relatively weak and some are strong [23]. The specific shape of these distributions can have a significant impact on the stability of theoretical ecosystem models [24,25], though its influence on structure is not well understood. Link-strengths for any observed ecological network are the estimates of the interactions among species within a community, and therefore all such networks are inherently probabilistic.…”

Section: Link-strength Variability In Predator -Prey Networkmentioning

confidence: 99%

Probabilistic patterns of interaction: the effects of link-strength variability on food web structure

Yeakel

Guimarães

Novák

et al. 2012

J. R. Soc. Interface.

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Patterns of species interactions affect the dynamics of food webs. An important component of species interactions that is rarely considered with respect to food webs is the strengths of interactions, which may affect both structure and dynamics. In natural systems, these strengths are variable, and can be quantified as probability distributions. We examined how variation in strengths of interactions can be described hierarchically, and how this variation impacts the structure of species interactions in predator -prey networks, both of which are important components of ecological food webs. The stable isotope ratios of predator and prey species may be particularly useful for quantifying this variability, and we show how these data can be used to build probabilistic predator -prey networks. Moreover, the distribution of variation in strengths among interactions can be estimated from a limited number of observations. This distribution informs network structure, especially the key role of dietary specialization, which may be useful for predicting structural properties in systems that are difficult to observe. Finally, using three mammalian predator -prey networks (two African and one Canadian) quantified from stable isotope data, we show that exclusion of link-strength variability results in biased estimates of nestedness and modularity within food webs, whereas the inclusion of body size constraints only marginally increases the predictive accuracy of the isotope-based network. We find that modularity is the consequence of strong link-strengths in both African systems, while nestedness is not significantly present in any of the three predator -prey networks.

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Section: Link-strength Variability In Predator -Prey Networkmentioning

confidence: 99%

Probabilistic patterns of interaction: the effects of link-strength variability on food web structure

Yeakel

Guimarães

Novák

et al. 2012

J. R. Soc. Interface.

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“…The population densities (N ) of each species i in a S-species community were governed by: where r i is the species specific population growth rate, K i is the species specific carrying capacity in the absence of competitors, and the strength and form of interspecific interactions (isj ) are indicated by a i,j . Here, we consider competitive interactions [0!a i,j !1], and the intraspecific interaction terms (a i,i ) were scaled to unity for all species, so that the intraspecific interaction was always stronger that interspecific interactions (Rees et al 1996;Kokkoris et al 2002). The interaction matrix was asymmetric, in accordance with field studies on symmetry of competitive interactions (Schoener 1983).…”

Section: Methodsmentioning

confidence: 99%

The impacts of different management strategies and environmental forcing in ecological communities

2006

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Understanding the effects of population management on the community a target species belongs to is of key importance for successful management. It is known that the removal or extinction of a single species in a community may lead to extinctions of other community members. In our study, we assess the impacts of population management on competitive communities, studying the response of both locally stable and unstable communities of varying size (between four and 10 species) to three different management strategies; harvesting of a target species, harvesting with non-targeted catch, and stocking of the target species. We also studied the consequences of selecting target species with different relative abundances, as well as the effects of varying environmental conditions.We show here how the effects of management in competitive communities extend far beyond the target population. A crucial role is played by the underlying stability properties of the community under management. In general, locally unstable communities are more vulnerable to perturbation through management. Furthermore, the community response is shown to be sensitive to the relative density of the target species. Of considerable interest is the result that even a small (2.5%) increase in the population size of the target species through stocking may lead to extinction of other community members. These results emphasize the importance of considering and understanding multi-species interactions in population management.

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“…The long-tailed nature of this distribution is due to the multiplicative analogue of the central limit theorem [47]. The shape, or parameterization, of these distributions can have a significant impact on the stability of theoretical ecosystem models [89,75], though its influence on topology is not well understood. An NLID can be constructed for both quantitative and probabilistic food-webs (see below).…”

Section: Strength Variance In Food-web Networkmentioning

confidence: 99%

“…As such, the presence of nestedness and modularity, as a function of link-strength, has not been assessed. This is of key importance because weak and strong links may di↵erently a↵ect species persistence after a perturbation [115,89].…”

Section: Introductionmentioning

confidence: 99%

“…Impacts of perturbations on food-web structure may be immediate or lagged [186]; they can a↵ect communities by reorganizing interactions [137], changing the magnitudes of interactions [89,14], or eliminating species [186,172]. However, observations of community organization across a perturbation event are typically confined to short timescales and to communities with fast turn-over rates.…”

Section: Introductionmentioning

confidence: 99%

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Dedication. Acknowledgments

2011

The Acquisition of German

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xvii Dedication xixAcknowledgments xx . See panel C. for a scenario where one prey is preferred over another. C. A tri-trophic system, where a top-predator consumes a meso-predator, which in turn consumes two prey. The sizes of the nodes denote relative abundance, and the thickness of the arrows denote the magnitude of the biomass flow. The top-predator in the leftmost network is relatively abundant, depressing the meso-predator population, thereby limiting the meso-predator's e↵ect on the two prey populations. The two rightmost networks (boxed) have reduced top-predator populations. In both cases, the meso-predator has greater abundance due to decreased predation pressure. However, in one scenario, both prey are preferred equally, resulting in apparent competition dynamics. In the second scenario, one prey is preferred over another, resulting in an asymmetric cascade. Such preferences could result from specific anatomical constraints of the meso-predator, a scenario explored in Chapter 4. C 1 and C 2 , and 4 prey: r 1 r 4 ) is represented by both pairwise interaction distributions for each link, and a network-level interaction distribution for the system. Link thickness represents the median link-strength, shown with the vertical bar in each pairwise interaction distribution. B-C. Both model food-webs X and Y have link-strengths drawn from the NLID. In model food-web X, the weights are distributed similar to the median weights of the empirical web (i.e. equivalent structure), but they are distributed di↵erently among nodes (i.e. alternative interactions). In model Y , the weight structure is di↵erent than that of the empirical web (i.e. alternative structure), and necessarily, the distribution of weights among nodes di↵ers as well (i.e. alternative interactions). Dotted nodes indicate those with link-strengths that di↵er from the median link-strengths of the empirical food-web. D-F. Given a single niche axis based on a continuous resource trait (e.g. body size) where prey are ranked from r 1 to r 4 , distributions of resource use are shown for the two consumers. Representations of dietary overlap illustrate higher similarity in diet between predators of the empirical system and model X, whereas the consumers in model Y have little dietary overlap, despite sharing the same NLID. 5 A-C. Sensitivity analyses of the Saskatchewan, Amboseli, and Lake Naivasha food-web ensembles, respectively. Similarity values for each cuto↵ (s i ) for Model 2 are on the y-axis, and the x-axis ranges from a lower standard deviation (SD) than the empirical SD to a higher SD (such that the empirical SD is central to the range; stippled vertical line). The colored data points represent the median similarity indices for each cuto↵ value (legend), while the top and bottom whiskers denote the 25 th and 75 th percentiles, respectively. The underlined values mark the standard deviation corresponding to the highest average similarity across cuto↵ values. For all systems, the highest average similarity is close to or exactly matches ...

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Variability in interaction strength and implications for biodiversity

Cited by 117 publications

References 38 publications

Probabilistic patterns of interaction: the effects of link-strength variability on food web structure

Probabilistic patterns of interaction: the effects of link-strength variability on food web structure

The impacts of different management strategies and environmental forcing in ecological communities

Dedication. Acknowledgments

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