Metabolic traits:
As with morphological traits, we also examined the effect of egg mass
and incubation temperature on metabolic traits across populations. As
egg mass increased, ∆mass decreased at the two southern populations, but
had no effect in northern populations (Table 2). However, comparison of
beta values across sites showed only a significant difference between AP
and SR. A positive influence of egg mass on residual yolk mass was
observed across all populations except for AP, but differences across
populations were not significant. Incubation temperature did not affect
∆mass or ∆BMI at any population, but exerted negative influences on ∆SVL
at YK and fat body mass at all populations (Table 2, Figure 3A). On the
other hand, there was a significantly positive influence of incubation
temperature on ∆TG and residual yolk mass (Table 2, Figure 3B) in at
least one population. Whereas the effect sizes of temperature on ∆SVL,
∆TG and fat body mass did not differ across sites, the influence of
temperature on residual yolk mass did, showing a reduction at YK (Table
2, Figure 3B).
When comparing phenotypes across populations after correcting for egg
mass, we found significant differences in fat body mass between at least
two populations at both 29.5°C and 33.5°C, with a trend for smaller fat
body masses at the northern populations (Figure 3A; Appendix 1).
Consistent with the decreased influence of incubation temperature on
residual yolk mass at YK, animals from 29.5°C at YK had significantly
higher residual yolk mass compared to WO (Figure 3B, Appendix 1). Upon
examination of the mass-corrected allocation of maternal resources
towards metabolic phenotypes, there were significant differences for
both residual yolk mass and fat body mass across populations. Animals
from the southern populations tended to allocate more resources towards
fat body mass than the northern populations (Figure 3C), and animals
from YK at 29.5°C allocated more resources towards residual yolk mass
relative to other populations (Figure 3D).
Incubation temperature had a negative influence on incubation duration
across all sites (Figure 4). The influence of temperature was greater at
the northern populations than at southern populations, driven by
comparatively shorter incubation periods at 33.5°C and longer incubation
periods at 29.5°C (Figure 4). However, differences across sites within
temperatures were not significant.