Abstract
The niche model has been widely used to model the structure of complex food webs, and yet the ecological meaning of the single niche dimension has not been explored. In the niche model, each species has three traits, niche position, diet position and feeding range. Here, a new probabilistic niche model, which allows the maximum likelihood set of trait values to be estimated for each species, is applied to the food web of the Benguela fishery. We also developed the allometric niche model, in which body size is used as the niche dimension. About 80% of the links in the empirical data are predicted by the probabilistic niche model, a significant improvement over recent models. As in the niche model, species are uniformly distributed on the niche axis. Feeding ranges are exponentially distributed, but diet positions are not uniformly distributed below the predator. Species traits are strongly correlated with body size, but the allometric niche model performs significantly worse than the probabilistic niche model. The best-fit parameter set provides a significantly better model of the structure of the Benguela food web than was previously available. The methodology allows the identification of a number of taxa that stand out as outliers either in the model's poor performance at predicting their predators or prey or in their parameter values. While important, body size alone does not explain the structure of the one-dimensional niche.
Highlights
Understanding the diversity and distribution of interspecies interactions is a vital challenge for developing our understanding of complex ecosystems
We examine the best-fit (MLE) parameter values of the model to better understand the reasons for the successes and failures of the niche model, and to interpret the meaning of the various species parameters, in how they relate to body sizes in the food web
The overall fit of the probabilistic niche model to the Benguela food web is significantly better than that of any of the models tested in two recent studies that computed the likelihoods of various food web models, including the best-performing model to date [18,31]. This improved performance occurs because the way in which the probabilistic niche model allows gaps in the exactly interval diets of the original niche model more closely mirrors the niche structure of the empirical data than the non-interval niches used in the minimum potential niche model or other niche model variants
Summary
Understanding the diversity and distribution of interspecies interactions is a vital challenge for developing our understanding of complex ecosystems. The simplest representation of a food web, in which both species and interactions between species are represented as present or absent from the system, ignores many details but captures the topological structure related to the energy transfer processes occurring in the system. These binary food webs provide a tractable representation of ecological complexity, and their structure has important consequences for many aspects of ecosystem function, including the relationship between network complexity and system stability [3], their robustness and resilience to species extinctions [4] and their resilience in the face of environmental change [5]. These include models coupling evolutionary and population time scale [6,7], models of food web assembly [8], studies of the effects of body size on the persistence of species in food webs [9], and models of network topology including models grounded in mechanistic concepts such as foraging theory [10,11], and the stochastic structural food web models that are the focus of this work
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
