Abstract: I will discuss how vertebrate skin colours and skin appendages (scales, feathers, hairs, ...) are patterned through Turing and mechanical instabilities. First, I will show that Reaction-diffusion (RD) models are particularly effective for understanding skin colour patterning at the macroscopic scale, without the need to parametrise the profusion of variables at the microscopic scales. I suggest that the efficiency of RD is due to its intrinsic ability to exploit continuous colour states and the relations among growth, skin-scale geometries, and the (Turing) pattern intrinsic length scale. Second, I will show that a three-dimensional mechanical model, integrating growth and material properties of embryonic skin layers, captures most of the dynamics and steady-state pattern of head scales in crocodiles.

Bio: Michel Milinkovitch is Full Professor in the Department of Genetics & Evolution at the University of Geneva (Switzerland). He is also a member of the Institute of Genetics and Genomics in Geneva (iGE3) since its foundation (2011) and a Group leader of the Swiss Institute of Bioinformatics (SIB) since 2014. As an evolutionary geneticist, he contributed to quantitative analysis and modelling in Molecular Phylogenomics and Applied Evolutionary Genetics. He has developed concepts, analytical tools, and algorithms/models for multiple sequence alignments, phylogeny inference and haplotypic network building. His recent focus is on Evolutionary Developmental Genetics (Evo-Devo) and the Physics of Biology. He specialises on non-classical model species in reptiles and mammals and integrates data and analyses from comparative genomics, molecular developmental genetics, as well as computer modelling and numerical simulations.