Food web framework for size-structured populations

TL;DR

This paper introduces a novel size-structured food web framework that integrates traditional food web concepts with size-spectrum modeling, enabling detailed analysis of ontogenetic growth, life-history omnivory, and community structure.

Contribution

It develops a new size-structured food web model that incorporates ontogenetic growth and trait-based parameters, validated through analytical solutions and cross-species data analysis.

Findings

Analytical power-law community spectrum matches complex model predictions.

Biomass distribution aligns with size and maturation traits.

Predicted diversity varies with size at maturation.

Abstract

We synthesise traditional unstructured food webs, allometric body size scaling, trait-based modelling, and physiologically structured modelling to provide a novel and ecologically relevant tool for size-structured food webs. The framework allows food web models to include ontogenetic growth and life-history omnivory at the individual level by resolving the population structure of each species as a size-spectrum. Each species is characterised by the trait 'size at maturation', and all model parameters are made species independent through scaling with individual body size and size at maturation. Parameter values are determined from cross-species analysis of fish communities as life-history omnivory is widespread in aquatic systems, but may be reparameterised for other systems. An ensemble of food webs is generated and the resulting communities are analysed at four levels of organisation: community level, species level, trait level, and individual level. The model may be solved analytically by assuming that the community spectrum follows a power law. The analytical solution provides a baseline expectation of the results of complex food web simulations, and agrees well with the predictions of the full model on 1) biomass distribution as a function of individual size, 2) biomass distribution as a function of size at maturation, and 3) relation between predator-prey mass ratio of preferred and eaten food. The full model additionally predicts the diversity distribution as a function of size at maturation.