Include the females: morphology-performance relationships vary between sexes in lizards.

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.

Urban wall lizards are resilient to high levels of blood lead.

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.

3D printed models are an accurate, cost-effective, and reproducible tool for quantifying terrestrial thermal environments.

Predicting ecological responses to rapid environmental change has become one of the greatest challenges of modern biology. One of the major hurdles in forecasting these responses is accurately quantifying the thermal environments that organisms experience. The distribution of temperatures available within an organism's habitat is typically measured using data loggers called operative temperature models (OTMs) that are designed to mimic certain properties of heat exchange in the focal organism. The gold standard for OTM construction in studies of terrestrial ectotherms has been the use of copper electroforming which creates anatomically accurate models that equilibrate quickly to ambient thermal conditions. However, electroformed models require the use of caustic chemicals, are often brittle, and their production is expensive and time intensive. This has resulted in many researchers resorting to the use of simplified OTMs that can yield substantial measurement errors. 3D printing offers the prospect of robust, easily replicated, morphologically accurate, and cost-effective OTMs that capture the benefits but alleviate the problems associated with electroforming. Here, we validate the use of OTMs that were 3D printed using several materials across eight lizard species of different body sizes and living in habitats ranging from deserts to tropical forests. We show that 3D printed OTMs have low thermal inertia and predict the live animal's equilibration temperature with high accuracy across a wide range of body sizes and microhabitats. Finally, we developed a free online repository and database of 3D scans (https://www.3dotm.org/) to increase the accessibility of this tool to researchers around the world and facilitate ease of production of 3D printed models. 3D printing of OTMs is generalizable to taxa beyond lizards. If widely adopted, this approach promises greater accuracy and reproducibility in studies of terrestrial thermal ecology and should lead to improved forecasts of the biological impacts of climate change.