SSI radiating populations have larger craniofacial trait values
than Caribbean or SSI generalist-only populations.
The results of Bayesian mixed-effects model suggest that on average the
SSI radiating group has larger trait values (mean trait value: 0.06,
95% HDI: 0.03, 0.09) than either the Caribbean (mean trait value:
-0.09, 95% HDI: -0.13, -0.05) or SSI generalist-only groups (mean trait
value: -0.07, 95% HDI: -0.11, -0.03; Figure 3). Model estimates for
each trait indicate that this pattern was reflected in 13 of the 18
traits, while 5 of the 18 traits showed no significant differences
between groups (Appendix Table D1).
We also included species as a fixed effect in this model to account for
the expected differences in trait values between species. We found that
on average generalists (mean trait value: 0.039, 95% HDI: 0.020, 0.058)
had larger trait values than both snail-eaters (mean trait value: -0.11,
95% HDI: -0.17, -0.046) and scale-eaters (mean trait value: -0.031,
95% HDI: -0.075, 0.013; Appendix Figure D1.A), however, this pattern is
variable depending on the trait. For instance, scale-eaters have larger
estimates of lower jaw length and lower estimates of maxillary head
protrusion compared to both generalists and snail-eaters (Appendix Table
D2).
Finally, we investigated the effects of population in our model and
found that populations did not have significantly different trait value
estimates (Appendix Figure D1.B). We also examined the variability of
estimates due to population ID for each craniofacial trait. The standard
deviation reported for 16 of the 18 traits was below 0.1 indicating that
populations generally have similar trait values. The exceptions being
maxillary head height and nasal tissue protrusion, which had higher
standard deviations of 0.25 and 0.16 respectively (Appendix Figure
D1.C).