(a) Adhesion between two cells is mediated by receptors and ligands (represented by a bitstring, see Hogeweg, 2000). The receptor of one cell is matched to the ligand of the other cell and vice …
(a) A population of cells moves by chemotaxis towards the peak of the gradient, which in this season is located at the left boundary of the grid. (b) At the end of the season, cells divide, the …
(a) Distance of the centre of mass of cells from the peak of the gradient as a function of time, for different values of (five independent runs for each value), together with the average …
(a) The movement of a single cell. (b) Typical movement of a cluster of strongly adhering cells, and of the cells inside the cluster. Cells are placed on the right of the field and move towards …
(a) Multicellularity () rapidly evolves in a population of cells with . (b) Multicellularity only evolves when seasons are sufficiently long ; unicellular strategies evolve when seasons are …
We let a simulation run for MCS and then record the distance from the peak of the gradient, for two different populations of cells - one non-adhering (in red, ) and one adhering (in blue, ), …
(a) We log-log transformed the data (the shaded area is the relative error ). (b) We fitted a polynomial function to the data, then took the derivative of the polynomial function. (c,d) …
For each cluster size, we ran five independent simulations. Each dot corresponds to one simulation. Their average (per cluster size) generates the line. All other parameters as in main text.
(a) With chemoattractant gradient. (b) Without chemoattractant gradient. In both cases cells with are placed at the centre of the field (All other parameters as in main text).
(a) . (b) . In both cases cells with are placed on the right of the field and move towards higher concentration of the gradient (the semicircle indicates the resource location, where the …
The plots show the displacement over time of the centre of mass of a single cell (indigo) and that of a cluster of 50 cells (green). Note that the x axis is different in different plots. The value …
The plots show the displacement over time of the centre of mass of a single cell (indigo) and that of a cluster of 50 cells (green). The value of used in main text is indicated by the Default …
Each line corresponds to one simulation with a given combination of number of cells N and cell size , and shows the distance of the centre of mass of the cluster of cells from the peak of the …
(a) Visual explanation of the algorithm, with a cartoon representation of a cell track with cell positions recorded at regular time intervals. Images 1-4 represent subsequent stages of the …
The data for adhering cells are taken from the same simulation used for main text Figure 5a, over 10 seasons after reaching evolutionary steady state with MCS. Black: all vs. all surface tension …
For , the inset shows the surface tension for MCS. All other parameters and initialisation are as in main text Figure 5a.
All other parameters and initialisation are as in main text Figure 5a.
All other parameters and initialisation are as in main text Figure 5.
All other parameters and initialisation are as in main text Figure 5.
(a) The emergence of collective chemotaxis when individual cells cannot sense the gradient; (b) the evolution of multicellularity (and uni-cellularity) under these conditions. - the strength of …
All cells have the same colour to show how the migration of the cluster as a whole resembles that of an amoeba.
Cell colour indicates the direction of migration, to emphasise the streaming dynamics within the cluster.
The season changes every MCS.
The season changes every MCS. For all cells . Mutation rate is set to zero to emphasise the spatial population dynamics.
The season changes every MCS. For all cells . Mutation rate is set to zero.
Parameter | Explanation | Values |
---|---|---|
lattice size | 500 × 500 lattice sites | |
T | Boltzmann temperature | 16 AUE |
cell stiffness | 5.0 AUE/[lattice site]2 | |
cell targetarea | 50 lattice sites | |
Cell adhesion | ||
minimum J value between cells | 4 AUE/[lattice site length] | |
minimum J value between cell and medium | 8 AUE/[lattice site length] | |
length of receptor and ligand bitstring | 24 bits | |
length ligand bitstring for medium adhesion | six bits | |
Cell migration and chemotaxis | ||
strength of persistent migration | 3.0 AUE | |
duration of persistence vector | 50 MCS | |
strength of chemotaxis | 1.0 AUE | |
scaling factor chemoattractant gradient | 1.0 molecules/[lattice site length] | |
probability of zero value (’hole’) in gradient | 0.1 [lattice site]−1 | |
Evolution | ||
N | population size | 200 cells |
duration of season | 5 × 103 - 150 × 103 MCS | |
hd | distance from gradient peak where fitness is | 50 [lattice site length] |
receptor and ligand mutation probability | 0.01 per bit, per replication |
AUE: Arbitrary Units of Energy (see Hamiltonian in Model Section); lattice site: unit of area; lattice site length: unit of distance; MCS: Monte Carlo Step (unit of time).