A theoretical perspective on how tripartite interactions between immunity, microbiota and pathogens affect pathogen virulence evolution

• Applicant: Dr. Mathias Franz
• Subject Area: Evolution, Anthropology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 425876005

In the proposed project I aim to conduct theoretical studies on how tripartite interactions between the hosts, its microbiota and pathogens affect pathogen virulence evolution. The related complexity of these interactions generates serious challenges for (1) thoroughly understanding pathogen virulence evolution and (2) testing theoretical predictions in empirical studies. The overarching goal of the proposed project is to provide insights and tools on how to deal with this complexity. Within this context, I aim to derive predictions, which are testable in a wide range of empirical settings. Specifically, I aim to address the following four objectives. Objective 1 aims to fill the gap in theoretically founded predictions for single tripartite interaction mechanisms. Objective 2 will assess potential synergistic or antagonistic effects among multiple mechanisms. In Objective 3 I will investigate causal links between tripartite interaction mechanisms and pathogen virulence evolution. Thus, instead of identifying mechanism-specific predictions, here I aim to understand how higher-level patterns, such as variation in host resistance, mediate the effects of tripartite interactions on virulence evolution. The ultimate goal here is to derive predictions that are testable without mechanistic information on tripartite interactions. Objective 4 will assess if it is necessary to consider the host microbiota as a community of interacting species or if a single-species conceptualization is sufficient. To address my objectives, I will be expanding on a recently published conceptual framework on how tripartite interactions between the hosts, its microbiota and pathogens affect pathogen virulence evolution. The proposed theoretical studies will include minimalistic models that are analytically tractable and more complex simulation models that describe tripartite interactions in more detail. During the proposed project I will increase model complexity in a step-wise manner, which aims at (1) facilitating the analysis of more complex models and (2) assessing the generality of the gained insights.

• DFG Programme: Research Units
• Subproject of: FOR 5026: Integrating insect immunity, microbiota and pathogens