DIEP seminar by Pierre Haas
Examples of emergence in ecology and morphogenesis
In this talk, Pierre will give three examples of different kinds of emergent behaviour in very different biological systems, starting with a curious example of the emergence of stability in ecological communities. He will show that the possibility of stable coexistence in ecological communities with Lotka-Volterra dynamics emerges from "irreducible" communities. Pierre will futher explain how our exhaustive analysis of all networks of competitive, mutualistic, and predator-prey interactions of N<6 species suggested that, strikingly, these irreducible ecologies form an exponentially small subset of all ecologies, as do the mathematically curious "impossible ecologies" in which stable coexistence is non-trivially impossible. He will briefly outline the rich mathematical structures hiding in this problem.
Next, Mr. Haas will turn to an example of the emergence of shape from mechanical instabilities and geometry in development: Morphogenesis is often the active result of cellular deformations within a tissue, but can also be passive, resulting from forces applied at tissue boundaries by neighbouring active tissues. The ateendees will be introduced to the Drosophila hindgut primordium as a physical model for this boundary-driven morphogenesis. They will be shown how we combined experimental quantification and physical models to reveal how a mechanical bifurcation breaks the symmetry of the shape of the hindgut and how the geometry of ellipsoidal embryo robustly selects the orientation of this shape.
Finally, he will give an example revealing how complex macroscopic dynamics can emerge from microscopic mechanics in morphogenesis. The biological context for this example is epithelial gap closure, a crucial tissue movement during development that requires cell rearrangements at the edge of the closing gap. Mr Haas will show how these plastic cell intercalations interact with the elasticity of the tissue by coarse-graining a minimal model of cell intercalations. Their work reveals that different macroscopic closure dynamics can emerge at the tissue scale from the details of the microscopic energy barrier to intercalation. As an application, this explains the mechanical role of the tissue fluidisation observed in the serosa closure process of the beetle Tribolium.
Pierre Haas is an applied mathematician who did his doctoral work with Prof. Raymond E. Goldstein FRS. His work was recognised by the Award for Outstanding Doctoral Thesis Research in Biological Physics of the American Physical Society. Pierre received Nevile Research Fellowship in Cambridge and a Hooke Research Fellowship in Oxford, before moving to Dresden in 2021, where he leads the research group "Self-Organisation of Multicellular Systems" at the Max Planck Institute for the Physics of Complex Systems and the Max Planck Institute of Molecular Cell Biology and Genetics.
If you wish to attend this seminar online, please send an email to r.lier@uva.nl to receive the zoom-link.