Tracking ecological processes along community trajectories

Populations of different species interact with one another in a myriad ways. Ecological communities are defined by the rich tapestry of species populations in a given spatiotemporal scale, alongside the interactions between individuals of the same and other species. Understanding the processes and patterns inherent to ecological communities is a fundamental goal of ecological sciences. From a fundamental perspective, community properties in general cannot be directly inferred from species attributes, and therefore require adopting different conceptual frameworks and methodologies, often based on the study of complex systems, their structure and dynamics. From an applied point of view, key ecosystem functions also arise at the interplay of species composition and interactions, so that their management necessarily involves a deep understanding of community processes and patterns. Communities are inherently dynamic, because their composition may change across space and time, and because the interactions may also vary. Furthermore, each of these components may respond differently to external factors. A central question in community ecology is therefore to what extent the emergent properties of communities are maintained as their components (populations or their individual interactions) change - not unlike the paradox of Theseus ship. The dynamic nature of ecological communities is widely acknowledged, but our understanding and tools to study them are still based on static simplifications: the stability of ecological communities is assumed to rely on equilibrium states, analyses of their interaction networks are nearly always based on single snapshots with static interactions, and analysis of species composition are generally disconnected from these on species interactions, taking them as separate compartments and even fields of research. Therefore, we cannot understand with the current paradigms how changes in species composition, biomass, or interactions feed back into each other and determine emergent properties like community stability or ecosystem functions. Jointly analysing changes in species composition and changes in species interactions is a novel frontier in community ecology that will help understand how community dynamics play out and respond to global change. This perspective will further provide a better understanding of community stability by linking complementary measures currently analysed in isolation, opening new ways to quantify the trajectories of ecological communities across space and time. In TESEO, we will pioneer a unified analysis of community trajectories, linking in a coherent ecological framework the spatiotemporal variability in species composition, biotic interactions and the feedbacks between these two components. For doing so we will develop novel ecological theory, methodologies and insights from model and empirical systems.