The impact of non-linear functional responses on the long-term evolution of food web structure

TL;DR

This study explores how different non-linear functional responses influence the long-term structure of evolving food webs, highlighting the importance of predator focus and adaptive foraging in forming complex ecosystems.

Contribution

It demonstrates that specific non-linear functional responses promote the emergence of large, multi-layered food webs with realistic link distributions.

Findings

Complex webs form only with predator focus on best prey

Standard responses lead to mostly basal species webs

Weak links naturally emerge from evolution

Abstract

We investigate the long-term web structure emerging in evolutionary food web models when different types of functional responses are used. We find that large and complex webs with several trophic layers arise only if the population dynamics is such that it allows predators to focus on their best prey species. This can be achieved using modified Lotka-Volterra or Holling/Beddington functional responses with effective couplings that depend on the predator's efficiency at exploiting the prey, or a ratio-dependent functional response with adaptive foraging. In contrast, if standard Lotka-Volterra or Holling/Beddington functional responses are used, long-term evolution generates webs with almost all species being basal, and with additionally many links between these species. Interestingly, in all cases studied, a large proportion of weak links result naturally from the evolution of the food webs.