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As species move into new environments through founder events, their phenotypes may diverge from native populations. Identifying the drivers underlying such variation and the constraints on the adaptive potential of this variation is essential for understanding how organisms respond to new or rapidly changing habitats. Such phenotypic divergence may be especially evident in populations introduced to new environments via human-assisted transport or in dramatically altered environments such as cities. Sexually dimorphic species beg the additional questions of how these new environments may influence the sexes differently and how dimorphism may shape the range of potential responses. The repeated translocation, establishment, and spread of wall lizards (Podarcis spp.) from native European populations to new locations in North America provide an excellent natural experiment to explore how phenotypes may differ after establishment in a new environment. Here, we quantify body shape and the multivariate morphological phenotype (incorporating limb dimensions and head length) of common wall lizards (P. muralis) and Italian wall lizards (P. siculus) in replicated North American introductions. In both species, males are larger and have larger head length and limb dimensions than females across all sampled groups. Sexual dimorphism in the multivariate morphological phenotype was of similar magnitude when comparing native and introduced populations for both species, though the trajectory angles in multivariate trait space differed in P. siculus. When comparing introduced lizards from contemporary and historically collected museum specimens, we identified differences of similar magnitude but in different trajectories between sexes in P. siculus, and differences in both magnitude and direction of sexual dimorphism in P. muralis. These idiosyncratic patterns in phenotypic trajectories provide insight to the potential array of processes generating phenotypic variation within species at the intersection of invasion biology and urban evolution. 

Thermoregulatory decisions impact nearly every aspect of the physiology, performance, and ecology of ectotherms. Thus, understanding the factors which influence ectotherm thermoregulatory behaviors across ecological contexts and environmental conditions is essential in predicting responses to novel or changing environments. Specifically, quantifying such behaviors across the entire diel cycle – day and night – is key to understanding the impact on physiological processes that happen during periods of inactivity, such as digestion. Utilizing high-resolution time-series data, we quantified the diel cycle of thermoregulatory behaviors in fed and unfed common wall lizards (Podarcis muralis) over five consecutives days. We first tested the hypothesis that feeding status affects diurnal and nocturnal thermoregulation. Second, we quantified the impact of feeding status on patterns of consistency and correlation within and among individuals in diurnal and nocturnal thermoregulatory behaviors. Lizards modulated their behavior in response to feeding status, conserving energy by choosing lower temperatures when unfed and by seeking higher temperatures when fed. We observed consistent among-individual differences (repeatability) in thermoregulatory behaviors across diurnal and nocturnal periods. Furthermore, diurnal and nocturnal thermoregulatory behaviors were positively correlated within individuals. We demonstrate that this diurnal ectotherm actively thermoregulates during the night, a finding particularly pertinent in urban environments, where artificial light and heat can prolong the active period of lizards. Overall, this research provides valuable insight into the flexible thermoregulation strategies of a species highly successful in expanding its range, demonstrating the importance of considering both diurnal and nocturnal activity. 

Abstract Thermoregulatory decisions impact nearly every aspect of the physiology, performance, and ecology of ectotherms. Thus, understanding the factors which influence ectotherm thermoregulatory behaviors across ecological contexts and environmental conditions is essential in predicting responses to novel or changing environments. Specifically, quantifying such behaviors across the entire diel cycle—day and night—is key to understanding the impact on physiological processes that happen during periods of inactivity, such as digestion. Utilizing high-resolution time-series data, we quantified the diel cycle of thermoregulatory behaviors in fed and unfed common wall lizards (Podarcis muralis) over five consecutives days. We first tested the hypothesis that feeding status affects diurnal and nocturnal thermoregulation. Second, we quantified the impact of feeding status on patterns of consistency and correlation within and among individuals in diurnal and nocturnal thermoregulatory behaviors. Lizards modulated their behavior in response to feeding status, conserving energy by choosing lower temperatures when unfed and by seeking higher temperatures when fed. We observed consistent among-individual differences (repeatability) in thermoregulatory behaviors across diurnal and nocturnal periods. Furthermore, diurnal and nocturnal thermoregulatory behaviors were positively correlated within individuals. We demonstrate that this diurnal ectotherm actively thermoregulates during the night, a finding particularly pertinent in urban environments, where artificial light and heat can prolong the active period of lizards. Overall, this research provides valuable insight into the flexible thermoregulation strategies of a species highly successful in expanding its range, demonstrating the importance of considering both diurnal and nocturnal activity. 

Synopsis As species move into new environments through founder events, their phenotypes may diverge from native populations. Identifying the drivers underlying such variation, and the constraints on the adaptive potential of this variation, is essential for understanding how organisms respond to new or rapidly changing habitats. Such phenotypic divergence may be especially evident in populations introduced to new environments via human-assisted transport or populations in dramatically altered environments such as cities. Sexually dimorphic species beg the additional questions of how these new environments may influence sexes differently and how dimorphism may shape the range of potential responses. The repeated translocation, establishment, and spread of wall lizards (Podarcis spp.) from native European populations to new locations in North America provide an excellent natural experiment to explore how phenotypes may differ after establishment in a new environment. Here, we quantify body shape and the multivariate morphological phenotype (incorporating limb dimensions and head length) of common wall lizards (P. muralis) and Italian wall lizards (P. siculus) in replicated North American introductions. In both species, males are larger and have larger head length and limb dimensions than females across all sampled groups. Sexual dimorphism in the multivariate morphological phenotype was of similar magnitude when comparing native and introduced populations for both species, though the trajectory angles in multivariate trait space differed in P. siculus. When comparing introduced lizards from contemporary and historically collected museum specimens, we identified differences of similar magnitude but in different trajectories between sexes in P. siculus, and differences in both magnitude and direction of sexual dimorphism in P. muralis. These idiosyncratic patterns in phenotypic trajectories provide insight to the potential array of processes generating phenotypic variation within species at the intersection of invasion biology and urban evolution. 

ABSTRACT Nocturnal temperatures are increasing at a pace exceeding diurnal temperatures in most parts of the world. The role of warmer nocturnal temperatures in animal ecology has received scant attention and most studies focus on diurnal or daily descriptors of thermal environments' temporal trends. Yet, available evidence from plant and insect studies suggests that organisms can exhibit contrasting physiological responses to diurnal and nocturnal warming. Limiting studies to diurnal trends can thus result in incomplete and misleading interpretations of the ability of species to cope with global warming. Although they are expected to be impacted by warmer nocturnal temperatures, insufficient data are available regarding the night‐time ecology of vertebrate ectotherms. Here, we illustrate the complex effects of nocturnal warming on squamate reptiles, a keystone group of vertebrate ectotherms. Our review includes discussion of diurnal and nocturnal ectotherms, but we mainly focus on diurnal species for which nocturnal warming affects a period dedicated to physiological recovery, and thus may perturb activity patterns and energy balance. We first summarise the physical consequences of nocturnal warming on habitats used by squamate reptiles. Second, we describe how such changes can alter the energy balance of diurnal species. We illustrate this with empirical data from the asp viper (Vipera aspis) and common wall lizard (Podarcis muralis), two diurnal species found throughout western Europe. Third, we make use of a mechanistic approach based on an energy‐balance model to draw general conclusions about the effects of nocturnal temperatures. Fourth, we examine how warmer nights may affect squamates over their lifetime, with potential consequences on individual fitness and population dynamics. We review quantitative evidence for such lifetime effects using recent data derived from a range of studies on the European common lizard (Zootoca vivipara). Finally, we consider the broader eco‐evolutionary ramifications of nocturnal warming and highlight several research questions that require future attention. Our work emphasises the importance of considering the joint influence of diurnal and nocturnal warming on the responses of vertebrate ectotherms to climate warming.