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Abstract Predicting potential distributions of species in new areas is challenging. Physiological data can improve interpretation of predicted distributions and can be used in directed distribution models. Nonnative species provide useful case studies. Panther chameleons (Furcifer pardalis) are native to Madagascar and have established populations in Florida, USA, but standard correlative distribution modeling predicts no suitable habitat forF. pardalisthere. We evaluated commonly collected thermal traits– thermal performance, tolerance, and preference—ofF. pardalisand the acclimatization potential of these traits during exposure to naturally-occurring environmental conditions in North Central Florida. Though we observed temperature-dependent thermal performance, chameleons maintained similar thermal limits, performance, and preferences across seasons, despite long-term exposure to cool temperatures. Using the physiological data collected, we developed distribution models that varied in restriction: time-dependent exposure near and below critical thermal minima, predicted activity windows, and predicted performance thresholds. Our application of commonly collected physiological data improved interpretations on potential distributions ofF. pardalis, compared with correlative distribution modeling approaches that predicted no suitable area in Florida. These straightforward approaches can be applied to other species with existing physiological data or after brief experiments on a limited number of individuals, as demonstrated here. 

Procedures to obtain skin secretions in frogs may induce stress from handling or injection with stress-associated hormones (norepinephrine). We investigated the metabolic costs of procedures used to assess amphibian antimicrobial capacity and skin microbiome. We randomly assigned 48 adult coqui frogs (Eleutherodactylus coqui) to four treatments: microbiome depletion, antimicrobial peptide (AMP) depletion, microbiome and AMP depletion, and an unmanipulated control group. Microbiome depletion was achieved by soaking frogs in an antibiotic cocktail bath, whereas the AMP depletion was done by injection of norepinephrine followed by a buffer bath. We used a flow-through Sable Systems Field Metabolic System to collect respirometry data following a 30-minute acclimation period to respirometry chambers. Respirometry data were collected at three timepoints: (1) Baseline at 2-3 weeks prior to treatment; (2) Post-treatment representing 2 days after AMP depletion and 4 days after microbiome depletion; and (3) Final data at 6 weeks post-treatment. Then, to assess the effects of norepinephrine injection at a shorter timescale, a subset of 24 frogs that had not previously experienced AMP depletion were assigned to either AMP depletion or a buffer bath-only control group. Respirometry data collection began without acclimation to respirometry chambers, immediately after removing frogs from buffer baths. Over the 6-week period, we found no consistent treatment effects on metabolism in coqui frogs. At the shorter timescale, metabolism increased with time-since-handling and after norepinephrine injection. Our results show that standard procedures predicted to increase stress at the individual level do not have a lasting effect on whole-frog metabolism. 

The potential emergence of Batrachochytrium salamandrivorans (Bsal) in North America threatens salamander diversity and ecosystem functioning, thus an understanding of mechanisms influencing host survival during infection is key to predict future impacts. Previous studies indicate that temperature plays a role in regulating infection dynamics, in that access to a thermal gradient provides the means to prevent infections. Phenotypic flexibility is a likely mechanism, as temperature can enhance (or suppress) host functional capacity in both lunged and lungless salamanders. However, we know very little about how hosts are using thermal environments to achieve effective immune gene expression during Bsal infection. Through a series of experiments, we aim to 1) reveal if interspecific differences in disease susceptibility and functional responses are exacerbated by thermal environments, 2) determine if hosts can minimize the metabolic costs of infections by selecting optimal environments, and 3) project susceptibility risk across the landscape using information about species’ thermal preferences. We discuss our plans to evaluate immune gene expression, metabolic rates and thermoregulation relating to infection with Bsal and access to different thermal environments in plethodontid salamanders from Florida. Additionally, to develop models to predict infection susceptibility, we are seeking collaborations in compiling data on thermal preferences and thermal limits across plethodontid salamander species. 

An underlying rule in biology is that temperature affects physiological processes. This is salient in ectothermic organisms such as herpetofauna, which must cope with the challenges of changing body temperatures. The limitations associated with living in a dynamic thermal environment often translate into patterns of herpetofaunal distribution and behavior. As such, an understanding of thermal physiology and thermal environment are foundational to studies of herpetofauna. Beginning with a brief review of the contributions of Hal Heatwole and Hal Cogger to the field of thermal ecology, I explore how some methodologies and have changed over time with technological improvements to tackle emergent issues including invasion by herpetofauna and understanding of disease processes. I discuss recent applications of thermal ecology in my own research to understand and predict distribution of invasive herpetofauna, and to understand disease processes in wild populations. Specifically, I discuss the predictive value of critical thermal minima on current and future distributions of invasive lizards introduced to Florida, USA (Leiocephalus carinatus and Furcifer pardalis), obtained through different experimental and computational methods. I also discuss planned methodologies to assess the role of thermoregulation in combatting infection of Batrachochytrium dendrobatidis and B. salamandrivorans in plethodontid salamanders.