# The Critical Role of Coefficients: Updating Allometric Normalisation Constants for Modern Ecology and Modelling

## TL;DR

This paper updates allometric coefficients for metabolism and production using modern data and methods, showing their impact on ecological modeling.

## Contribution

New allometric coefficients for metabolism and production derived using phylogenetic hierarchical modeling.

## Key findings

- Updated coefficients are mostly lower than previous estimates with increased uncertainty.
- Using new coefficients increases biomass and species persistence in food web models.
- Stability in food web models remains unchanged despite updated coefficients.

## Abstract

Allometry, the scaling of traits or biological rates with body mass, is central to a wide range of ecological research including dynamic food web modelling. There has been extensive focus on exponents (3/4 scaling laws), but little on the coefficients (normalisation constants). Coefficients that have been used since 2006 are derived from limited data and dated methodologies. Here, we compiled a data set of over 1000 genera with body mass spanning 10 orders of magnitude. We updated metabolism and production coefficients, deriving new genus and metabolic group levels estimates with phylogenetic hierarchical modelling providing robust inference. Our coefficients were mostly lower than those previously estimated, with increased uncertainty estimates. We used the Bioenergetic Food Web Model to evaluate their impact, finding increased biomass and species persistence but no change in stability. Our coefficients pave the way for future simulations that take advantage of subsets of genus and metabolic group data.

Allometry is central to a wide range of ecological research including dynamic food web modelling. Here we updated the often neglected allometric coefficients for metabolism and production, deriving new genus and metabolic group levels estimates with phylogenetic hierarchical modelling providing robust inference. We show that using the updated coefficients influence the results of Bioenergetic Food Web Models, increasing total biomass and species persistence estimates.