Table 3. External to internal branch length ratio test, implemented in clonal frame.
| Population | External/ internal branch length ratio (95% confidence interval) | Significance |
|---|---|---|
| Phylotype I | 2.528 (1.413–4.271) | 0.0013** |
| Phylotype II | 1.367 (0.988–1.810) | <0.001*** |
| Phylotype IIA | 1.918 (1.166–3.038) | 0.0016** |
| Phylotype IIB | 1.362 (0.837–2.281) | 0.037* |
| Phylotype III | 2.647 (1.480–4.577) | <0.001*** |
| Phylotype IV | 1.331 (0.832–2.189) | 0.150 (NS) |
Abbreviation: NS, not significant; *, significant; **, highly significant; ***, very highly significant. If the ratio is significantly higher than expected, the inferred genealogy is considered as unexpectedly ‘star-like', which is consistent to either an expansion of the population size or the acquisition of a fitness advantage early in the history of the sample (Didelot and Falush, ClonalFrame UserGuide version 1.1; den Bakker et al. (2008).