Table 1.

Results from averaged linear mixed models examining the relationship between phenotypic divergence and a series of predictor variables, including migration category (divide or no divide). Models were run with family and genus as nested random variables and phenotypic divergence as a dependent variable (for all traits combined (a) and each set of traits separately (bd)). Fixed effects included migration category, time since divergence (p-distance, the proportion of nucleotide sites that differ between clades); geographical overlap, migration distance, breeding latitude, and body mass. Only fixed effects included in the final model are shown; those that are significant predictors of phenotypic divergence (where confidence intervals (CI) do not overlap zero) are shown in bold. Negative parameter estimates for migration category indicate that groups with migratory divides tend to have lower phenotypic divergence than groups without divides. n = number of models in final averaged model (i.e. within ΔAICc of 2), R2 = goodness-of-fit of the global model.

predictor variablesparameter estimatesstandard errorslower CIUpper CI
(a) overall phenotypic divergence (R2 = 0.56, n = 4)
 (intercept)1.731.27−0.794.25
 migration category−0.440.11−0.65−0.22
 time since divergence0.220.0470.130.32
 breeding latitude−0.510.35−1.220.20
 body mass0.230.0980.030.43
(b) song divergence (R2 = 0.37, n = 6)
 (intercept)−0.00571.59−3.173.16
 migration category−0.580.17−0.92−0.25
 time since divergence0.190.0730.0390.33
 geographical overlap−0.480.55−1.580.62
 breeding latitude0.430.53−0.631.50
 migration distance0.300.17−0.0360.63
(c) colour divergence (R2 = 0.38, n = 9)
 (intercept)1.181.69−2.194.55
 migration category−0.450.18−0.81−0.084
 time since divergence0.240.0850.0720.41
 geographical overlap1.100.61−0.132.32
 breeding latitude−0.520.61−1.750.71
 body mass0.300.17−0.0410.64
(d) morphological divergence (R2 = 0.29, n = 4)
 (intercept)5.282.210.849.72
 time since divergence0.180.0760.0280.33
 geographical overlap0.710.47−0.231.65
 breeding latitude−1.280.56−2.410.14