Mathematical models can help us to enhance our understanding of a specific observation by exploring its characteristics under a wide range of conditions, including those that cannot be addressed by empirical tests. Moreover, mathematical models allow us to generalize specific observations made in a particular taxon and thereby transfer them to a large range of organisms.
In the project, we use mathematical models (A4.1, PI Traulsen) and fine-tune them with the help of empirical data from an experimentally accessible metaorganism system (A4.3, PI Schulenburg) with the aim to improve our general understanding of the evolution of host-microbiota interactions.
The origin and evolution of these interactions are still largely unclear. A particular challenge is that a multitude of microorganisms and a host organism are likely to have conflicting evolutionary “interests”, yet still form a novel unit that as a whole is subject to selection. How does selection at the higher hierarchical level (i.e., imposed by the host) interact with selection at the lower levels (i.e., determined by the microbes)? How important are different types of interactions or trophic levels within the microbial community for the characteristics of the metaorganism? Are the interactions mainly driven by ecological relationships and neutral processes? What exactly determines the initial formation of the association and thus evolution of a host-associated life cycle of the microbes?
During the first funding phase, we explored the influence of hierarchical levels (e.g., determined by phages) on metaorganism function and evolution. We also established a model on neutral dynamics within the metaorganism and applied it to wide range of study systems from the CRC.
In the second funding phase, we will use the developed mathematical models and experimental approaches to explore in an iterative form the exact fitness determinants of microbes within the metaorganism, taking into account their transmission dynamics, different interaction types, trophic levels, and also neutral processes. Microbe fitness components will be related to fitness of the host. We anticipate that the utilization of mathematical models and their combination with tailored experiments will provide an integrated understanding of the evolutionary and ecological processes that shape and determine the initial origin of the metaorganism, its subsequent evolution, and the resulting functions.
In sum, our project specifically focuses on microbe fitness which is still understudied, yet represents a highly potent driver of host-microbiota interactions. We postulate microbe fitness to be of particular importance during the initial formation of these associations. Moreover, our project specifically assesses the influence of neutral in comparison to selective processes during formation and maintenance of host-microbiota interactions. Our project takes advantage of the particular power of mathematical modelling to generalize across empirical findings and explore a wide range of conditions. Our project combines mathematical modelling with a tailored experimental approach in an iterative form, in order to validate theoretical predictions and yield insight for further development of the models.
Our project thus directly links the complementary expertise of two groups, one with particular competence in evolutionary mathematical model development and analysis (Traulsen group) and the other with comprehensive experience in experimental evolution and evolutionary analysis of a highly tractable study system (Schulenburg group).