Table 2. Fits of models to empirical data on changing colour frequencies (Figure 3) and comparisons between models.
| Colour | Model log likelihood (−2LL) estimates | Model comparisons | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Migration | Directional selection | Heterozyg. advantage | Frequency dependent | M vs DS | M vs HA | M vs FD | DS vs HA | DS vs FD | HA vs FD | |
| Parameters/test | 2 | 2 | 3 | 3 | ΔAIC | χ12 | χ12 | χ12 | χ12 | ΔAIC |
| White-1 | 104.3 | 117.7 | 87.8 | 85.6 | −13.4 | 16.4*** | 18.6*** | 29.8*** | 32.0*** | 2.2 |
| White-2 | 75.6 | 70.0 | 70.0 | 69.6 | 5.5 | 5.5† | 6.0* | 0.0 | 0.5 | 0.5 |
| White-3 | 73.7 | 72.2 | 72.2 | 71.4 | 1.5 | 1.5 | 2.3 | 0.0 | 0.9 | 0.9 |
| White-4 | 53.9 | 58.5 | 52.4 | 51.7 | −4.7 | 1.5 | 2.2 | 6.2* | 6.8** | 0.6 |
| White combined | 307.3 | 318.4 | 282.4 | 278.3 | −11.1 | 24.9*** | 29.1*** | 36.0*** | 40.1*** | 4.1 |
| Banded-1 | 99.5 | 98.8 | 98.8 | 98.4 | 0.7 | 0.7 | 1.1 | 0.0 | 0.4 | 0.4 |
| Banded-2 | 80.7 | 80.7 | 80.7 | 78.9 | 0.1 | 0.1 | 1.9 | 0.0 | 1.8 | 1.8 |
| Banded-3 | 86.9 | 87.3 | 86.3 | 86.1 | −0.4 | 0.6 | 0.8 | 1.0 | 1.2 | 0.2 |
| Banded combined | 267.2 | 266.8 | 265.7 | 263.3 | 0.4 | 1.4 | 3.9 | 1.0 | 3.4 | 2.4 |
| Red | 111.6 | 116.8 | 108.0 | 108.6 | −5.2 | 3.6† | 3.0† | 8.9** | 8.2** | −0.6 |
Abbreviations: AIC, Akaike information criterion; DS, directional selection; FD, frequency-dependent selection; HA, heterozygote advantage; Heterozyg., heterozygote; M, migration.
Negative values indicate that the latter of the two models in the comparison had the higher likelihood value. In χ2 tests; d.f.=1 for single population model comparisons, d.f.=4 for White combined and d.f.=3 for banded combined. Bold log-likelihood estimates indicate the best models.
†P<0.1, *P<0.05, **P<0.01, ***P<0.001 (after sequential Bonferroni correction for repeated tests of white and banded skerries).