Table 1. Models of the evolutionary trajectory of a community.
| Model |
Parameters |
Expected ratio (r) at time t | |||
|---|---|---|---|---|---|
| Initial MT:LT ratio (r0) | Waiting time (tw) | Slope of change in ratio (m) | Steady-state ratio of two ecotypes (r∞) | ||
| Null | Yes | No | No | No | r=r0 over all times |
| Single-ecotype | Yes | Yes | Yes | No | r=r0 until time tw; log r=log r0+m (t - tw) after tw |
| Multi-ecotype | Yes | Yes | Yes | Yes | r=r0 until time tw; log r=log r0+m (t - tw) after tw and before r reaches r∞; r=r∞ after r reaches r∞ |
The initial-ratio parameter r0 was estimated directly from the initial MT and LT colony counts; the parameters for waiting time (tw), slope (m) and the steady-state ratio (r∞) were estimated to fit the observed trajectories of MT:LT ratio with maximum likelihood, as described in the text. The likelihood of the model yielding an observed ratio at a given time was based on the empirical Gaussian distribution of the ratio (Supplementary Figure 1). Yes and no indicate whether a parameter was included within a given model.