Weak trophic position-body mass relationships undermine simple size spectrum models for coral reefs

Unravelling food web dynamics across biological communities is a central goal of ecology. In size-structured ecosystems, the shape of trophic pyramids is often inferred from the distribution of biomass across body-mass classes, i.e. its size spectrum. Size-spectrum analysis has become a popular tool to study the ecosystem functioning of aquatic ecosystems, including highly diverse coral reefs. However, the key assumption behind size spectra, i.e. that body size directly and positively correlates with trophic position, has rarely been directly evaluated in these systems. Here, we test this assumption by quantifying body mass, population densities and estimating trophic position from stable isotopes for 325 fish species across four Indo-Pacific locations. Consistent with prior studies, we found a positive relationship between biomass and body mass. However, weak and variable relationships between body mass and trophic position led higher biomass in primary consumers than in predators, as ..., , , # Weak trophic position-body mass relationships undermine simple size spectrum models for coral reefs

[https://doi.org/10.5061/dryad.tmpg4f58c](https://doi.org/10.5061/dryad.tmpg4f58c)

## Description of the data and file structure

This folder is composed of one .Rmd file and five datasets, including three .xlsx files and two .csv files.

The .Rmd file is called Analyses&Figures.Rmd

It contains the code to produce all of the figures of the corresponding manuscript except figure 1 (theoretical framework) and figure 2 (sampling maps). It uses all five datasets provided. 

The code also produces the model results displayed in the Supplementary Tables T1 to T2. 

The Analyses_Figures_2025.Rmd file is decomposed into six main sections:

* Data and packages uploading
* Biomass ~ Delta Nitrogen analyses and plots
* Biomass ~ Body mass analyses and plots
* Delta Nitrogen ~ Body mass analyses and plots
* Fig. 3 and S1 Table construction
* Biomass ratios ~ Delta Nitrogen analyses and plots

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