Hypertensive Toads: Investigating the Physiological and Evolutionary Pathways to Salt Tolerance in Amphibians

PROJECT SUMMARY My lab focuses on understanding the evolutionary and physiological mechanisms that enable salt-sensitive freshwater organisms, such as anuran amphibians, to develop resilience in saline environments. Chronic exposure to elevated salt levels, whether from environment or diet, can cause detrimental health effects for frogs and humans alike, as neither are well-equipped to manage excessive internal salt. However, my previous research has shown that some anuran species have adapted to tolerate elevated salt levels, allowing them to establish populations in coastal brackish habitats. We leverage the problem-solving power of adaptive evolution to understand how selection shaped physiological pathways that enhance salinity tolerance while also investigating how evolution mitigates the long-term costs of chronic salt exposure. This research will uncover new physiological strategies for coping with elevated salt levels, shed light on the broader risks associated with long-term salt exposure, and identify alternative mechanisms for reducing the costs of high salt intake, which may contribute to the development of solutions aimed at reducing the health effects of high-salt diets in humans. My previous work has identified several physiological and evolutionary mechanisms that likely contribute to anuran persistence in saline habitats. These discoveries form the foundation of this research, which will comprehensively test and validate these candidate mechanisms. Specifically, we will pursue two research directions: 1) investigating the physiological mechanisms of salt tolerance in coastal anurans over short timescales and 2) assessing the long-term costs of chronic salt exposure and how adapted populations mitigate these challenges. By comparing coastal and inland populations of two sympatric Hyla (treefrog) species that exhibit different physiological and adaptive responses to saltwater, we aim to understand how selection addresses the physiological challenges of salt stress across timescales and across levels of evolutionary divergence. Our integrative and comparative approach will utilize a suite of experimental and physiological assays that incorporate genetic, environmental, and temporal variables, to rigorously test key evolutionary and physiological hypotheses underlying salt tolerance. In addition to expertise in local adaptation and amphibian osmoregulatory biology, our lab is fully equipped with the necessary tools for the physiological assays, molecular analyses, and experimental methodologies described herein. These resources enable us to effectively address key questions across multiple biological levels—from molecular to organismal—ensuring a comprehensive understanding of salt tolerance. Ultimately, our research will uncover physiological strategies for managing elevated salt levels, highlight the broader risks of chronic exposure, and identify mechanisms that mitigate the long-term costs of chronic salt exposure. We expect to uncover new and alternative pathways for addressing the health challenges posed by chronically high sodium intake in humans and amphibians.