1. The thermal regimes experienced by a reptilian egg can influence phenotypic traits (size, sex, shape, locomotor performance, etc.) of the hatchling that emerges from that egg. Natural nests of the oviparous scincid lizard Bassiana duperreyi in the Brindabella Range of south-eastern Australia show strong seasonal shifts in temperature: first and last weeks of incubation often differ by >5°C.
2. Eggs of B. duperreyi were incubated under thermal regimes with identical overall mean values for average temperature and diel range, but differing in the sequence of temperatures. Some eggs were kept at 18 ± 5°C throughout incubation; others went gradually from cool (16 ± 5°C) to warm (20 ± 5°C); and others from warm (20 ± 5°C) to cool (16 ± 5°C).
3. These treatments significantly modified not only incubation periods (stable mean temperatures delayed hatching), but also hatchling traits: progressively decreasing temperatures yielded hatchlings with a higher incidence of deformities, smaller body size, relatively longer tails, and reduced locomotor performance than siblings from increasing temperatures.
4. Seasonal shifts in incubation temperatures are widespread, and may generate important variation in hatchling phenotypes. Sensitivity to such shifts may influence phenomena such as nest-site selection, the seasonal timing of nesting, and the evolution of viviparity.
- Nest temperatures
- Phenotypic plasticity