# Identifying conversion efficiency as a key mechanism underlying food webs evolution : a step forward, or backward ?

## TL;DR

This paper demonstrates that incorporating size-dependent biomass conversion efficiency into evolutionary food web models is crucial for realistic food web development, challenging previous assumptions of trait evolution independence.

## Contribution

It introduces a general model that relaxes arbitrary assumptions, showing size-dependent biomass conversion efficiency is essential for realistic food web evolution.

## Key findings

- Realistic food webs can evolve when biomass conversion efficiency depends on species size.
- Ignoring size dependence leads to unrealistic food web structures.
- The robustness of existing evolutionary models is questioned.

## Abstract

Body size or mass is one of the main factors underlying food webs structure. A large number of evolutionary models have shown that indeed, the adaptive evolution of body size (or mass) can give rise to hierarchically organised trophic levels with complex between and within trophic interactions. However, these models generally make strong arbitrary assumptions on how traits evolve, casting doubts on their robustness. In particular, biomass conversion efficiency is always considered independent of the predator and prey size, which contradicts with the literature. In this paper, we propose a general model encompassing most previous models which allows to show that relaxing arbitrary assumptions gives rise to unrealistic food webs. We then show that considering biomass conversion efficiency dependent on species size is certainly key for food webs adaptive evolution because realistic food webs can evolve, making obsolete the need of arbitrary constraints on traits' evolution. We finally conclude that, on the one hand, ecologists should pay attention to how biomass flows into food webs in models. On the other hand, we question more generally the robustness of evolutionary models for the study of food webs.