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

Parent-offspring conflicts are widespread given that resources are often limited. Recent evidence has shown that availability of 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 a protocol previously used on the viviparous form. Females were captured in early gravidity from six populations along a 600 m altitudinal gradient to investigate whether environmental conditions (altitude, water access and temperature) 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 with altitude, probably due to long term acclimation or local adaptation. This moderate water-based intergenerational conflict in gravid females contrasts sharply with previous findings for the viviparous form, with implications to the evolutionary reversion from viviparity to oviparity. It is likely that oviparity constitutes a water-saving reproductive mode which might help mitigate intensive temperature-driven population extinctions at low altitudes