Habitat choice favours local adaptation at the thermal niche margin. Growth rate = fitness estimation of cells from each patch through a quantification of increased optical density per hour from a small number of cells from each patch, fitted from population growth curves using gcfit function (grofit R-package) with spline fit. Gene_flow_level = level of dispersal toward the focal population (10% or 30% of the local population' initial carrying capacity). Time = time when growth rate measurements were performed, in weeks from the beginning of the experiment. Gene_flow_treatment = types of gene flow, with or without habitat choice.