Abstract

The formation of complex tissues during development relies on robust spatiotemporal coordination of mechanical forces between different tissues or in complex geometries. In the first part of this talk, I will show how this interplay of tissues and forces underpins the first folding event in the developing zebrafish forebrain [1]. I will develop a minimal fluid mechanical model of tissue flows during zebrafish gastrulation to identify the minimal set of spatiotemporally varying force singularities required and sufficient to reproduce the observed tissue flows qualitatively and quantitatively, respectively. I will then discuss how we have tested these predictions in vitro, highlighting how our combined experimental and theoretical results show how the coordination of different mechanical processes in different tissues is required for correct folding of the zebrafish forebrain.

Identifying the principles that determine stability of coexistence in ecological communities is an eternal problem of theoretical ecology. In the second part of this talk, I will develop a new approach to this question: I will analyse all networks of competitive, mutualistic, and predator-prey interactions of N≤5 species by random sampling of interaction strengths to reveal that the probabilities of stable coexistence can vary over many orders of magnitude even in ecologies that differ only in the network arrangement of identical ecological interactions. I will also uncover the role of very rare “impossible” and “irreducible” ecologies in determining the possibility of stable coexistence. Overall, this stresses the importance, compared to mere statistical trends, of the full structure of the network of interactions for stability of coexistence in ecological communities.

[1] A. Inman, J. E. Lutton, E. Spiritosanto, M. Tada, T. Bretschneider, P. A. Haas, and M. Smutny, biorxiv:2023.06.21.545965v1 (2023)

[2] Y. Meng, Sz. Horvát, C. D. Modes, and P. A. Haas, arXiv:2309:16261 (2023)