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Geometry Shapes Evolution of Early Multicellularity

Figure 4

Total number of cells resulting from different rates of cell death and geometric constraints.

A) Total number of living cells in groups with maximum node degree 3 in 100 simulations at 4 different probabilities of cell death. The highest probability of death ( in blue) has the largest number of cells and the greatest variance in final cell number. B) Same as A but with maximum node degree 4. Once again the highest probability of death ( in blue) produces the most cells. C) The same as B but the volume constraints are removed, i.e. the maximum node degree is still 4 but there is no limit to the number of cells in each shell. The probability of death no longer increases the population of cells. D) The mean number of living cells when a cell's susceptibility to death is delayed by 0–5 generations ( time units) since it last reproduced. The colors correspond to probabilities of death: (blue), (red), (green), (black); and the line style represents the degree cap: no cap (solid), 4 (dashed), 3 (dotted). In trees with degree caps of 3 and 4, the highest probability of death results in even more cells when death is delayed one generation but less as death is delayed further. In all other cases, delaying death results in less cells.

Figure 4