Embryonic Development in Two High-Elevation Oviparous Lizard Species: Contrasting Strategies for Coping With Cold...

Understanding how species respond to local climates is crucial for predicting their responses to climate change. The cold climate of high elevations constitutes a physiological challenge for reptiles, especially during the embryonic stages of oviparous species, because embryos have limited ability to thermoregulate behaviorally. To examine how high-elevation lizards maximize hatching success under cold climates, we compared reproductive traits and the temperature dependence of embryonic development in two lizard species occupying contrasting mountain microhabitats: the forest-dwelling Sphenomorphus taiwanensis and the grassland-dwelling Takydromus hsuehshanensis. We quantified embryonic stage at oviposition, measured post-oviposition embryonic developmental duration across a range of constant temperatures (15°C-34°C), and recorded shallow-soil temperatures in forests and open sites in their habitats. We found that T. hsuehshanensis laid early-stage embryos that appeared to require warm nesting sites to complete development, whereas S. taiwanensis laid advanced-stage embryos capable of completing development in the cool forest environment. These results suggest that these species use two distinct strategies: T. hsuehshanensis primarily uses a behavioral strategy (maternal nest-site selection), whereas S. taiwanensis primarily uses a physiological strategy (maternal egg retention). These strategies appear to be closely associated with their habitats' thermal characteristics (cold forest vs. warm grassland). By linking microhabitat thermal regimes to reproductive strategies-maternal egg retention versus nest-site selection-our findings provide a basis for anticipating species-specific responses to shifting mountain temperature regimes.