A call for a systematic approach to documenting physiological diversity in squamates and beyond

As anthropogenic climate change and urbanization continue to elevate global temperatures, understanding how ectotherms respond physiologically to temperature is of increasing importance. Squamates (lizards and snakes) have a history of serving as models for studies in thermal biology. Comparisons of physiological responses among different species or populations of the same species could provide insight into the capacity of these organisms to adapt to changing thermal environments. However, we rarely document the physiological phenotype of voucher specimens, and current research lacks clear methodological standardization, which potentially creates biases when making direct comparisons and performing analyses. To address this problem, we propose the 'physiotype' as a standardized, comprehensive framework for documenting the thermal physiology of squamates. We envisage the physiotype as an integrated suite of physiological traits that can function as a comparative tool, much like a morphological phenotype. Here, we recommend a standardized methodology for defining the physiotype, including an array of established measurements taken at ecologically relevant temperatures. Implementing this approach will enable robust comparative analyses, allowing for a more holistic understanding of how squamate physiology influences and is influenced by ecology and behavior. To maximize the utility of this approach, we also advocate for the creation of accessible repositories for physiotypes, which could facilitate large-scale data synthesis. This proposed methodological framework will enhance our ability to predict species' vulnerabilities and forecast their capacity for thermal adaptation, and will inform future conservation strategies across a thermally dynamic landscape.