Life-history divergence underlies elevation-specific warming responses in a plateau viviparous lizard

Climate warming may benefit cold-adapted reptiles by alleviating thermal constraints, but it can also impose physiological costs. How these outcomes are mediated by elevation-specific life-history strategies remains poorly understood. We conducted a semi-natural warming experiment on the Qinghai toad-headed lizard (Phrynocephalus vlangalii) at two contrasting elevations (2600 m and 3600 m) on the Qinghai-Xizang Plateau to evaluate its effects on maternal reproduction and offspring performance. Life-history divergence caused by environmental conditions drove the elevation-specific responses to warming. Warming consistently advanced maternal post-hibernation emergence and parturition at both elevations without reducing reproductive success or investment. Warming accelerated offspring growth, improved pre-hibernation body condition and sprint performance but did not increase telomere attrition. A trade-off was observed between neonatal quality and postnatal growth: warmed neonates were smaller at birth but grew faster than controls. Crucially, warming elicited contrasting survival responses across elevations: at the 2600 m, it further reduced neonatal quality and pre-hibernation survival was positively related to birth mass; at the 3600 m, pre-hibernation survival was unrelated to birth mass and enhanced under warming. Overall, warming may offer fitness advantages for cold-adapted reptiles. Nevertheless, the balance of benefits and costs depends on elevation-specific life-history strategies and physiological limits, underscoring the need to incorporate these factors in predicting species' responses to climate change.