A multi‐trait evaluation of patterns and fitness consequences of breeding phenology plasticity with nocturnal warming and food restriction in a lizard

Abstract Faced with climate warming, ectothermic species shift their breeding phenology, which is in part attributed to an acceleration of gestation or incubation in warmer environments. Thermal acceleration of gestation may have important fitness implications for breeding females and their offspring by impacting maternal homeostasis, embryonic development and hatching date, but these benefits and costs have been poorly documented. In addition, while climate change is characterised by a stronger trend for night‐time than for daytime warming and concurrent alterations of food availability, few studies have quantified phenology‐trait effects of increasing nocturnal temperatures and decreasing food intake. Here, we exposed female common lizards ( Zootoca vivipara ) to contrasted nocturnal temperatures and prey availability during gestation. We investigated multiple traits to quantify the functional impacts of nocturnal warming and food availability on breeding phenology, maternal condition, physiology and behaviour, current reproductive output and both females and offspring life‐history traits. Nocturnal warming advanced parturition dates, but food restriction further accelerated gestation and females' muscle catabolism under moderate nocturnal warming. Nocturnal warming and food restriction during gestation had negative effects on reproductive output and increased physiological imbalances in breeding females. Hot nocturnal temperatures down‐regulated basal corticosterone levels and immunocompetence, while food restriction reduced the antioxidant capacity of females. The thermal acceleration of gestation induced by nocturnal warming had positive effects on offspring life‐history traits related to fitness, such as endurance at birth and body growth during the first few months of life. By analysing multiple traits, our study provides an integrated understanding of the intra‐ and intergenerational effects of nocturnal warming and resource availability during gestation in a viviparous ectotherm. Our results underline the importance of considering nocturnal warming and resource availability as factors causing increased physiological imbalances and negative effects on ectotherm reproduction. They also show the need to consider the benefits and costs of phenological advances for breeding females and their offspring in order to improve our understanding of the consequences of phenological changes in the context of climate change. Read the free Plain Language Summary for this article on the Journal blog.