Mother-offspring conflict for water and its mitigation in the oviparous form of the reproductively bimodal lizard, Zootoca vivipara

Parent-offspring conflicts are widespread in nature given that resources are often limited. Recent evidence has shown that water can trigger such conflict during pregnancy in viviparous squamate species (lizards and snakes) and thus questions the role of water in the evolution of reproductive modes. Here, we examined the impact of water restriction during gravidity in the oviparous form of the bimodal common lizard (Zootoca vivipara), using the same protocol previously used in the viviparous form. Females were captured in early gravidity from six populations across a 600 m altitudinal gradient to investigate if environmental conditions (altitude, water access and temperature) may exacerbate responses to water restriction. Females were significantly dehydrated after water restriction, irrespective of their reproductive status (gravid vs. non-reproductive), relative reproductive effort (relative clutch mass), and treatment timing (embryonic development stage). Female dehydration together with reproductive performance varied along altitude, likely due to long term acclimation or local adaptation. This moderate waterbased intergenerational conflict in gravid females sharply contrasts to previous findings in the viviparous form, suggesting a potential implication in the reversion from viviparity to oviparity. Therefore, oviparity may constitute a water-saving reproductive mode which might help mitigate intensive temperature-driven population extinctions at low altitudes.