Collaborative Research: Evolving thicker skin: Understanding how adaptations to a universal trade-off dictate the climate vulnerability and ecology of an imperiled vertebrate clade

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Climate change is pushing many organisms towards their limits, forcing species to move, evolve, or risk extinction. Frogs are among the most vulnerable species on the planet with roughly a third already under threat of extinction. Frogs, and other amphibians, can breathe across their skin. However, their permeable skin leaves frogs sensitive to changes in temperature and humidity, which we expect with climate change. Thus, understanding frog skin is key to understanding how frogs will react to climate change. Yet, our knowledge of anuran skin evolution is surprisingly lacking. This project aims to measure variation in skin form and permeability and determine how skin variation affects key survival traits, like their ability to breathe and avoid dehydration. Our proposal accomplishes a major goal in ecology by incorporating organismal physiology into predictions of climate vulnerability while simultaneously expanding our knowledge of a critically threatened animal group. Furthermore, frog “skin breathing” provides a framework to communicate complex topics ranging from evolution (e.g., convergence and adaptation) to physiology (e.g., oxygen transfer and water loss) to conservation (e.g., climate change). This project will: 1) mentor Native American students at USU and historically excluded students at ISU in research and 2) generate a low-cost, interactive, and publicly accessible frog skin activity focused on inquiry and discovery-based learning of evolutionary concepts.Our proposal seeks to understand how a universal constraint underlying gas exchange dictates climate vulnerability and ecology in an imperiled vertebrate clade. Balancing the need for gas exchange with the risk of dehydration creates predictable evolutionary trade-offs across the tree of life and has selected for adaptations that decouple gas exchange from water loss (e.g. unique nasal morphologies in mammals and birds, stomata density and size in plants). Despite understanding the role of these clade-specific adaptations for promoting life in xeric environments, we know relatively little about the evolution of universal structures, such as skin. With their nearly worldwide distribution and reliance on their skin for gas exchange, we use anurans as an ideal system to investigate how skin has evolved to balance oxygen uptake and water loss in response to varying environmental selection pressures. The proposed project has three aims: 1) quantify how frog skin has evolved over the past 200 million years and in-response to what abiotic and biotic factors, 2) experimentally test anuran skin’s ability to decouple respiration and water loss, and 3) incorporate physiological data into activity budget models to improve our understanding of current anuran distributions and life-history evolution and predict species’ vulnerability to future climate change. Our integration of morphology, physiology, and modeling will tie skin form and physiology to anuran ecology and biogeography to improve our understanding of anuran distributions, life-history evolution, and species’ vulnerability to future climate change.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.