# A Mechanism of Food‐Web Complexity Emergence Under Multiple Environmental Drivers

## TL;DR

This study explains how environmental factors like ecosystem size and productivity can lead to complex food webs through nonlinear responses and colonization-competition tradeoffs.

## Contribution

A new colonization-competition tradeoff framework explains how multiple environmental drivers shape food-web complexity.

## Key findings

- Topological complexity of ecological networks shows non-linear responses to environmental gradients.
- Minor environmental changes can significantly alter food-web complexity through shifts in species dominance.
- Results remain valid under varied parameters and relaxed assumptions about competition.

## Abstract

Understanding the mechanisms that drive the emergence and maintenance of food‐web complexity under multiple environmental drivers is a central challenge in metacommunity ecology. The environmental variables (ecosystem size, resource productivity, and disturbance) are often considered as potential drivers of complex ecosystems. However, how these factors shape food‐web complexity remains unclear. Here, we develop a colonization‐competition tradeoff framework for complex ecological network metacommunities including multiple environmental drivers. We found that the topological complexity of ecological networks, measured by species richness, connectance, omnivory, and mean food chain length, exhibits robust, non‐linear idiosyncratic responses to gradients in ecosystem size, resource productivity, or disturbance. The non‐monotonicity arises from shifts in the dominance hierarchy of basal species driven by colonization‐competition tradeoffs, which in turn cascade upwards to alter consumer community composition and network structure. Moreover, this result stays valid even when parameters are altered or the assumption of a strict competitive hierarchy is relaxed. It reveals that a minor change in these environmental determinants can result in significant implications for the complexity of trophic networks. Thus, this study offers a mechanistic explanation for the emergence of food‐web complexity driven by multiple environmental drivers.

This study demonstrates that the topological complexity of ecological networks, including metrics like species richness and connectance, exhibits nonlinear oscillatory responses to changes in ecosystem size, productivity, and disturbance. These findings reveal that even minor environmental alterations can significantly impact food‐web complexity, providing a mechanistic explanation for its emergence under multiple environmental drivers.