Group-selection via aggregative propagule-formation enables cooperative multicellularity in an individual based, spatial model
Fig 5
The effect of size-dependent selection (predation) on aggregation-based propagule formation.
Top row: terminal cooperator ratio, depending on various association (AC, x axis) and dissociation probabilities (D, y axis); bottom row: temporal dynamics of independent simulations at AC = 0.95, D = 0.3 (indicated by the white crosshair in the top row). First column (s = 7) corresponds to weakest, last column (s = 3) to strongest predation, cf. Eq 1. The middle case s = 5 is the same as in Fig 4F, right panel. Defectors suffer more from predation, because they are less associated, hence as the predation stress increases, the area where they win reduces considerably. As predation decreases, defectors do not suffer from predation load, and cooperators lose their advantage, especially when the association rate is larger than the dissociation rate (AC>D). If predation is effectively removed (s>7, also Fig 4F, left panel), cooperators can still survive at AC<D. For more details, see text and Figs E, F in S1 Text.