Fig. 5

Model description. a 10’000 cells were initialized individually by randomly assigning a value from a uniform distribution from 0 to 1 to protection level and each trait (basal protection, protection increase and protection decrease). For every time step the survival of each single cell was evaluated depending on its protection level. Independent of the environmental state 5% of the cells were randomly killed to permit reproduction. In addition, if the current environmental state was ‘stress’, cells were killed dependent on the protection level (phenotype) they were carrying at that specific time point. For surviving cells, the protection level was adapted individually depending on the encoded traits (genotype). Cells were then selected for reproduction with a negative dependency on the protection level. For a small fraction of the population (0.1%) one of the genetic traits was selected randomly and its value was mutated. A list of parameters and pseudocode of the computational model can be found in the Additional file 7: S7. b Survival and reproduction probabilities were modeled to be dependent on the current level of protection. Survival of a stress period increased with the level of protection a cell was carrying (blue line). Increasing the level of protection in the current time step led to a decrease in the probability to reproduce, thereby modeled a protection cost. c Schematic depiction of two possible genotypes that may arise from this evolution simulation. To illustrate the difference between the two genotypes their behavior is shown in a sequence of time steps (from left to right, green are favorable conditions, yellow warning and red stress conditions). The number of blue dots within a cell represents the protection level. A cell that had attained a cellular memory (upper panel) upregulates protection only when sensing a warning or stress event and maintains the protection (slow decay) despite protection being costly (decreased probability to reproduce). The lower panel shows a cell that has evolved a basal protection where a minimal level of protection is maintained during all time