Morphological traits:
Both egg mass and temperature exerted positive effects on hatchling mass across all populations (Table 2). However, whereas the influence of egg mass did not differ across sites (Figure 2A), temperature more strongly affected hatchling mass at YK compared to the other three populations (Figure 2B). In addition, there was a trend for a greater influence of incubation temperature on SVL at the northern populations relative to the southern populations, with the influence of temperature on SVL not significant in the latter (Figure 2C). Across other morphological traits, the influence of temperature was variable in both direction and magnitude, differentially affecting TG, HL, and HW in at least one population, while the influence of egg mass was not (Table 2).
We next examined the extent to which morphological phenotypes varied across populations within a temperature, including whether differences in the influence of incubation temperature were driven by variation at 33.5°C, 29.5°C, or both by comparing model means under a common egg mass. There were significant differences in trait values between at least two populations for all morphological traits after controlling for egg mass differences, with interpopulation variation in morphological traits occurring primarily at 29.5°C (Appendix 1). For instance, the influence of incubation temperature on mass of YK hatchlings was primarily driven by a reduction in mass at 29.5°C relative to the other populations (Figure 2B). This pattern was mostly consistent across additional traits that were differentially impacted by incubation temperature in at least one population (TG, HL, and HW), with the exception of SVL, which appeared to involve differences at both 29.5°C and 33.5°C (Figure 2C). Ratios of morphological traits to hatchling mass showed no significant differences across populations at either temperature.