Numerous studies have focused on the drivers of diversity and stability of communities, especially under global change. However, multi-dimensionality of ecosystems due to biotic components (e.g predation, competition and adaptive dynamics) and abiotic factors (e.g. disturbances, resource dynamics and their distinct attributes) cause context-dependent outcomes and challenge the predictions. There are still controversies around complex community dynamics under varying regimes, however, finding mechanistical explanations will illuminate the fate of multispecies assemblages. Using model microbial communities, consisting of bacterial prey and protist predator, combined with simulation modelling and advanced statistics, this thesis investigated the impact of imposed disturbances (i.e. increased dilution rates that simulate density-independent mortality as press or pulse disturbances) (i) on transient recovery dynamics of a simple microbial food web, and (ii) on bacterial abundance, diversity and community structure in the absence or presence of a protist predator. In addition, this thesis questioned the impacts of species interactions and rapid trait shifts, as a response to predation and competition, on the community dynamics and stability. Our results revealed that the predator suffered more from disturbances over longer time periods. Reduced predation pressure caused a transient phase of prey release during and even after disturbances. Recovery time depended on the strength and duration of disturbances, however, coupling to an alternative resource increased the chance of fast recovery and stabilized the communities. In multi-species prey communities, bacterial abundance, diversity, and community composition were more affected by predation than by the disturbances and resource dynamics. Predator abundance, on the other hand, was strongly affected by the type of disturbance imposed. Importantly, community attributes had differential sensitivities, as reflected by their different response and recovery dynamics. Prey community dynamics varied more temporally andwere less stable under predation stress, while prey diversity increased significantly. Predation rapidly induced anti-predation traits, which altered population dynamics of both prey and predator. More importantly, predator and the resistant prey, in turn, elevated the number of direct cause-effect relationships between the community members. Our findings are not limited to the studied system and can be used to understand the dynamic response and recovery potential of many natural predator-prey or host-pathogen systems. They can be used as a base for future studies to illuminate the debates on the future communities.:Summary
Zusammenfassung
1 Scope and Outline
2 General Introduction
2.1 Context dependency of community dynamics
2.2 Ecological disturbances
2.2.1 Transient dynamics and stability
2.2.2 Catastrophic shifts
2.3 Species interactions and evolutionary dynamics under environmental change
2.3.1 Species interactions and coexistence
2.4 Eco-evolutionary dynamics
2.5 Community assembly mechanisms
2.6 Dealing with complexities
2.6.1 Microbial model systems as a tool in ecology
2.6.2 Correlation, causation and the future of predictions
2.7 Aims of this study
3 Community Dynamics under Disturbances
3.1 Transient recovery dynamics of a predator-prey system
4 Interactions of Community Drivers
4.1 Interactions between predation and disturbances shape prey communities
5 Species Interactions and Evolutionary Dynamics Shaping Communities
5.1 Summary
5.2 Introduction
5.2.1 Predator-Prey Dynamics and Community Stability
5.2.2 Causal inferences
5.3 Aim of the study
5.4 Methods
5.4.1 Organisms
5.4.2 Microcosm experiments and estimation of species abundances
5.4.3 Statistical analysis
5.5 Results
5.5.1 Community dynamics
5.5.2 Dynamics of prey diversity and community stability
5.5.3 Causal links between the species dynamics
5.6 Discussion
5.7 Synopsis
6 General Discussion
6.1 Communities under disturbances: Predator{ prey dynamics
6.2 Temporal species dynamics and community assembly
Synthesis and Outlook
7.1 Increasing complexity of species interactions
7.2 Going further from causal links
7.3 Metacommunities
References
8 Appendix
8.1 Declaration of the authorship
8.2 Author contributions of published articles
8.3 List of publications and conference contributions
8.4 Acknowledgments
8.5 Supplementary material for Chapter 3
8.6 Supplementary material for Chapter 4
8.7 Supplementary material for Chapter
