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Evolution of multicellular life cycles under costly fragmentation

Fig 2

Model of life cycles.

(A) Multicellular units increase in size and fragment to produce new units. Cell division (b_i) and unit death (d_i) rates depend on the size of the unit and are determined by the environment. If the fragmentation process is costly, the division rate at the maturity size may be smaller than prescribed by the environment alone (see Eq (1)), the death rate at the maturity size may be larger than prescribed by the environment alone (see Eq (2)), and some cells may be lost upon the fragmentation (highlighted in blue). In this example, m = 4, so the unit fragments when it reaches five cells, one cell is lost in fragmentation and the remaining four are split by the fragmentation mode 2+2. (B) The fragmentation mode of cell clusters can be described by a sum of integers. All possible fragmentations of units of size 2, 3, and 4 are presented here. Different life cycles have different growth rates and we are looking for the fastest growth in this context.

doi: https://doi.org/10.1371/journal.pcbi.1008406.g002