Search for: All records

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 An animal's morphology influences its ability to perform essential tasks, such as locomoting to obtain prey or escape predators. While morphology–performance relationships are well-studied in lizards, most conclusions have been based only on male study subjects, leaving unanswered questions about females. Sex-specific differences are important to understand because females carry the bulk of the physiological demands of reproduction. Consequently, their health and survival can determine the fate of the population as a whole. To address this knowledge gap, we sampled introduced populations of common wall lizards (Podarcis muralis) in Ohio, USA. We measured a complete suite of limb and body dimensions of both males and females, and we measured sprint speeds while following straight and curved paths on different substrates. Using a multivariate statistical approach, we identified that body dimensions relative to snout-to-vent length in males were much larger compared with females and that body dimensions of P. muralis have changed over time in both sexes. We found that sprint speed along curved paths increased with relative limb size in both males and females. When following straight paths, male speed similarly increased as body dimensions increased; conversely, female speed decreased as body dimensions increased. Female sprint speed was also found to have less variation than that of males and was less affected by changes in body size and hindfoot length compared with males. This study thus provides insights into how selective pressures might shape males and females differently and the functional implications of sexual dimorphism. 

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. 

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. 

Living in urban environments presents many challenges to wildlife, including exposure to potentially toxic pollutants. For example, the heavy metal lead (Pb) introduces numerous health problems to all animals, including humans. The little work that has been conducted on lead toxicity in reptiles suggests that lizards may be extraordinarily resilient to very high levels of lead pollution, by either avoiding or mitigating the toxicity. To assess the impact of lead exposure, we measured field blood levels and tested for the effects on ecologically relevant performance measures in common wall lizards (Podarcis muralis) – a small reptile particularly capable of thriving in urban environments. We captured lizards from roadside and park habitats across Cincinnati, Ohio, USA, and quantified the concentration of lead in blood samples (n = 71 adult lizards). Lizards from roadside populations had higher blood lead concentrations than lizards from park populations, and females had higher blood lead concentrations than males regardless of habitat type. We then tested two aspects of lizard performance important for survival: (1) balance, a cognitively demanding task, to assess the effect of lead on cognition (N = 41), and (2) running endurance, an aerobic exercise dependent on oxygen (N = 43), to assess the impact of lead on blood oxygen-carrying capacity. We then used correlation analyses to quantify the relationship between lead levels and these ecologically-relevant performance measures. There was no effect of blood lead levels on running endurance, but contrary to our predictions there was a slight positive effect on balance performance, whereby lizards with higher blood lead concentrations slipped less often than lizards with lower blood lead concentrations. Understanding the effects of lead toxicity and resilience in a particularly resistant animal could help us better respond to public health and environmental pollution concerns. 

This is a short note describing an observation of a trifurcated tail and an analysis of tail regeneration rates of lizards among populations in Ohio. 

Many species exhibit color polymorphisms which have distinct physiological and behavioral characteristics. However, the consistency of morph trait covariation patterns across species, time, and ecological contexts remains unclear. This trait covariation is especially relevant in the context of invasion biology and urban adaptation. Specifically, physiological traits pertaining to energy maintenance are crucial to fitness, given their immediate ties to individual reproduction, growth, and population establishment. We investigated the physiological traits ofPodarcis muralis, a versatile color polymorphic species that thrives in urban environments (including invasive populations in Ohio, USA). We measured five physiological traits (plasma corticosterone and triglycerides, hematocrit, body condition, and field body temperature), which compose an integrated multivariate phenotype. We then tested variation among co‐occurring color morphs in the context of establishment in an urban environment. We found that the traits describing physiological status and strategy shifted across the active season in a morph‐dependent manner—the white and yellow morphs exhibited clearly different multivariate physiological phenotypes, characterized primarily by differences in plasma corticosterone. This suggests that morphs have different strategies in physiological regulation, the flexibility of which is crucial to urban adaptation. The white‐yellow morph exhibited an intermediate phenotype, suggesting an intermediary energy maintenance strategy. Orange morphs also exhibited distinct phenotypes, but the low prevalence of this morph in our study populations precludes clear interpretation. Our work provides insight into how differences among stable polymorphisms exist across axes of the phenotype and how this variation may aid in establishment within novel environments.