Decoding emergent patterns in large microbial communities through the prism of disordered systems

Natural ecosystems display an extraordinary diversity of species, a phenomenon that has recently attracted the interest not only of ecologists but also of theoretical physicists. In this talk, I will introduce a Generalised Lotka–Volterra model of ecological communities that accounts for random interactions among species and finite noise. Remarkably, this high-dimensional formulation predicts the emergence of a Gardner-like phase in the low-noise regime [1].

I will then show how this framework offers a powerful platform for interpreting the complexity of the human microbiota [2]. By analysing metagenomic data from healthy individuals and patients with inflammatory bowel disease, I will link different physiological states of the gut to distinct regimes of the Lotka-Volterra model, shaped by stochasticity and interaction heterogeneity. Finally, I will discuss how extending the model to include more realistic growth behaviors reveals stabilising mechanisms that remain effective even in highly diverse communities [3].

[1] A. Altieri, F. Roy, C. Cammarota, G. Biroli, Phys. Rev. Lett. 126 (2021) [2] J. Pasqualini, A. Maritan, A. Rinaldo, S. Facchin, E. V. Savarino, A. Altieri & S. Suweis, eLife14:RP105948 (2025) [3] I. Hatton, O. Mazzarisi, A. Altieri, M. Smerlak, Science 383 (2024)