On the following subject
"Effects of disturbances on the structure and dynamics of a food web: a modelling approach".
Supervisor: Jean-Christophe Poggiale
Co-director: Frédéric Ménard
Usually, the relationships between the fragility of food webs and their structure, on the one hand, and the generative processes responsible for these structures, on the other, are treated separately. In this thesis, we develop an eco-evolutionary assembly model that allows us to study these two relationships within a unified framework. For each of them, three levels of organisation are considered: the network, the motif (i.e. triplets of network species), and the species. The role of the evolutionary history of communities in the establishment of these structures is studied, as is their fragility. Firstly, we highlight the key role played by environmental evolutionary richness in the emergence of food web structures and their associated fragility. We also show that this evolutionary environmental richness plays an important role in the type of controls ('bottom-up' vs 'top-down') present in the communities. We then highlight the sub-structures of particularly fragile networks; sub-structures which, combined with other indicators at the species level, make it possible to strengthen predictions as to the fragility of these species. Finally, we study the emergence of the characteristic distribution of these substructures, or network motifs: although common patterns are observed, for example in the order of appearance, or 'fixation', of some of these motifs, we show that the speed of emergence seems to depend on the abiotic conditions of evolution.
Key words :
Food webs, modelling, population dynamics, disturbances, evolution, fragility