DAS PARADOXON DER MOOSTIERCHEN: Wie wirkt sich die Struktur von (benthischen) Konkurrenznetzwerken auf deren Stabilität aus?

01/04/2021 to 31/03/2024

Ecosystems all over the world are under enormous pressure and face dramatic changes. Predicting their responses to current and future challenges is key to protect or restore them. But how can we develop sustainable management strategies without having a fundamental understanding of the mechanisms that enable species coexistence and community stability? Such strategies require insights into the interplay between an ecosystem’s internal organisation – levels of interactions within and between species – and its external controls, such as abiotic physical disturbances. Ecological networks, where nodes represent species and links represent species interactions, provide a powerful tool to disentangle the different mechanisms at hand and to identify the feedback processes that play a key role in determining a system's stability.

In this project, we will analyse the dynamics of observed competition networks. The overarching goal is to understand the relation between community organisation and stability, and how this relation is shaped by different disturbance regimes. We will use benthic species directly competing for available space on the seabed as a study system. More precisely, we will use empirical observations of pairwise confrontations to construct what we call energy loss webs. These are networks in which the links represent biomass loss rates due to competition with other species. Observed loss rates will be used in combination with simulated data from agent-based spatial modelling in order to quantify both inter- and intraspecific interaction strengths. We will apply a network-stability approach originally developed for trophic networks in order to analyse the stability of the resulting interference-competition networks. In particular, we will quantify the feedback structure of these systems, identify key feedback loops and investigate the system's development over time in terms of species richness, stability and adaptive strategies of the organisms. This knowledge will allow us to formulate general conditions for stability and identify key drivers for change.

Our approach is part of a recent development in network science, which recognises the importance of interaction strengths for network dynamics. The project will underpin the role of functioning and dynamics in network theory, going beyond the traditional focus on network topology. It will provide, to our knowledge, the first direct empirical test of classic stability theory. It will furthermore deliver a new, observation-based and empirically tested null-model for systems of interference competition, in changing environments.