Modelling collective movement across scales: from cells to wildebeest
Speaker: Elaine Ferguson (University of Glasgow)
Collective movements are widespread across scales in biological systems, from the sub-organismal movements of groups of cells around the body, to the far-ranging movements of bird flocks and herds of large herbivores. A general modelling framework for inferring the mechanisms driving movement in such diverse systems could be very useful, providing clues as to how these movements might be controlled or conserved. We developed a range of candidate models for collective movement, based on advection-diffusion partial differential equations. These models incorporated a range of movement mechanisms, including interactions between individuals, responses to environmental gradients, and environmental depletion. Various approaches were considered for parameter estimation and model selection, which varied from frequentist, to pseudo-Bayesian, to fully Bayesian, and in their requirements for numerical model solutions. This toolbox of models and inference approaches was validated on data from three study systems; two small-scale in vitro cellular systems, involving movement of groups of human melanoma cells and Dictyostelium discoideum (slime mould) cells, and a third much larger-scale system, involving wildebeest movement in the Serengeti ecosystem. We thus drew conclusions about the particular mechanisms driving collective movement in each of these systems.