Water restriction causes an intergenerational trade-off and delayed mother–offspring conflict in a viviparous lizard

Parenting is costly and because the relationship between the mother and embryos is not mutualistic, mother–offspring conflicts may exist whenever resource are scarce. However, intergenerational trade-offs and conflicts resulting from limited access to water, a vital and depreciable resource, remain largely overlooked. In this study, we examined the physiological, reproductive and life-history responses to water restriction in the European Common Lizard (Zootoca vivipara). We hypothesized that, under water-limited conditions, pregnant females experience both short-term and long-term physiological impacts (dehydration and stress) underlying an allocation trade-off for water between mothers and offspring. Water restriction led to a decrease in body mass, and an increase in plasma osmolality (dehydration) and corticosterone concentration in both males and females. The extent of the dehydration was positively correlated with fecundity in females. This suggests a trade-off between maternal water balance and allocation of water to developing embryos during reproduction. Water restriction had no immediate effect on reproductive output or offspring morphology at birth. Yet, water restriction in pregnant females enhanced their reproductive effort the following year but reduced the early life growth and annual survival of their second-year offspring. These delayed fitness responses to water restriction in offspring and mothers suggest that water can trigger intergenerational conflicts as demonstrated for energy. Although the mediation of this conflict remains to be clarified, we hypothesized that it represents a selective force that influences reproductive strategies. A plain language summary is available for this article.