The local structure of trophic interactions influences communities' biomass and productivity
Eva Delmas, Daniel B. Stouffer et Timothée Poisot
UNIVERSITÉ DE MONTRÉAL

Amongst the consequences of the anthropogenic-driven crisis is the emergence of novel communities with changed diversities and structures. While understanding the consequences of shifts in diversity have been recognized as a central issue over the last decades, interactions have received less attention. Yet, interactions disappear at a higher rate than species and their impact on ecosystem functioning (EF) have been shown to be important. However, we do not fully understand how interactions influence EF in realistic communities. By providing the paths of biomass through communities, food webs provide an obvious framework to address this issue. We propose that the distribution of the different types of motifs provide an accurate predictor of ecosystem functioning. Motifs indeed represent different types of trophic interactions - thus different shapes of biomass transfers at a local scale. We applied a model of consumer-resource dynamics on both simulated and empirical systems and tested the influence of motifs distribution on ecosystem functioning within empirical communities. The first outputs of the model revealed that while motifs behave differently when studied in isolation, only apparent and exploitative competition distribution in empirical networks have an influence on its functioning. Previous study showed that communities' motifs profile is a generality of trophic networks and influence their stability. Our findings will allow to deepen our understanding of the causes and consequences of the profile of over- and under-representation of motifs, in addition to contribute to building a framework for predicting changes in EF in a context of communities shift.