Natural intra-species variability of S. cerevisiae cellular morphology. A) The panel of strains used in this study is shown on a neighbour-joining tree reflecting genetic distances. Branch lengths are proportional to the fraction of 101,343 segregating sites that differentiate each pair of strains, as described in . Colors reflect ecological annotations. B) Intra- versus inter-strain variability of morphological traits. Each dot represents one of 501 measured parameters. Orange and grey distinguish the traits that were called significant and non-significant by the Kruskal-Wallis test at FDR = 0.01, respectively. For the purpose of visual clarity, each parameter was transformed by f(x) = (x-μBY) / σBY, where μBY and σBY are the mean and standard deviations of the parameter across 34 replicates of the BY4743 strain. Note that significance inference was determined from ranks of raw values and was therefore not affected by this transformation. The sum of squares across replicates (x-axis) and across strains (y-axis) were then computed. The three parameters highlighted in red reflect distinct cellular properties : long over short axis ratio of the ellipse fitted to the mother cell (C115_A1B), angle of neck position (C105_A1B) and total mother cell size (C11-1_A1B). C) Boxplot representation of C115_A1B values for all strains. Box colors represent ecological origins as in A). Insets show representative images of the two extreme strains YJM269 (top) and CLIB192 (bottom) where mother cells are elongated and round, respectively, with fluorescent labelling of actin (red), DNA (blue) and cell wall (green). Bar : 5 μm. D-E) Similar representation for the two other traits highlighted in B). The strain order is the same in all three panels C, D and E.