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 http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13009/suppinfo is available for this article.

Summary Understanding proximate determinants of predation rates is a central question in ecology.Studies often use functional response (density dependent) or allometric (mass dependent) models but approaches that consider multiple factors are critical to capture the complexity in predatorprey interactions. We present a novel comprehensive approach to understand predation rates based on field data obtained from a vertebrate predator. 2. Estimates of food consumption and prey abundance were obtained from 21 semi-natural populations of the lizard Zootoca vivipara. We identified the most parsimonious feeding rate function exploring allometric, simple functional response and allometric functional response models. Each group included effects of sex and weather conditions. 3. Allometric models reveal the importance of predator mass and sex: larger females have the highest natural feeding rates. Functional response models show that the effect of prey density is best represented by a Holling type II response model with a mass, sex and weather dependent attack rate and a constant handling time. However, the best functional response model only received moderate support compared to simpler allometric models based only on predator mass and sex. 4. Despite this limited effect of prey densities on feeding rates, we detected a significant negative relationship between an index of preferred prey biomass and lizard density. 5. Functional response models that ignore individual variation are likely to misrepresent trophic interactions. However, simpler models based on individual traits may be best supported by some data than complex allometric functional responses. These results illustrate the importance of considering individual, population and environmental effects while also exploring simple models.

1. Reproduction involves considerable reorganization in an organism's physiology that incurs potential toxicity for cells (e.g., oxidative stress) and decrease in fitness. This framework has been the cornerstone of the so-called 'oxidative cost of reproduction', a theory that remains controversial and relatively overlooked in non-model ectotherms.2. Here, we used two complementary approaches in natural and controlled conditions to test whether altered access to climate conditions (water and temperature resources) alters oxidative status and mediates reproductive trade-offs in viviparous populations of the common lizard (Zootoca vivipara).3. First, we examined whether access to free-standing water and differences in ambient temperature across 12 natural populations could be related to variation in oxidative status, reproductive effort and reproductive success. Second, we determined whether an experimental restriction to water triggers higher oxidative cost of reproduction and correlates with fitness measures (reproductive success, future survival rate and probability of future reproduction). 4. Pregnant females exhibited higher sensitivity than males to natural or experimental limitations in temperature and water access. That is, in restricted environments, pregnant females with higher reproductive effort exhibited stronger oxidative damage despite enhanced non-enzymatic antioxidant capacity. 5. Enhanced antioxidant defensive capacity in pregnant females was positively correlated with higher reproductive success, whereas elevated oxidative damage negatively correlated with offspring annual survival.6. Altogether, our results revealed a context-dependent oxidative cost of reproduction that was concomitant with a conflict in water demand from offspring. These new insights should be critical for understanding ectotherm responses to heat waves and summer droughts that are increasing in frequency and duration.