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Reptile and amphibian (herpetofauna) populations face a substantial risk of decline, with potentially cascading consequences for ecosystem function. Effective conservation requires an understanding of their adaptive capacity, and examining responses to past environmental change can provide valuable insight. Stable isotope analysis is a widely used method for reconstructing ecological and physiological patterns in both modern and ancient organisms, yet it remains underutilized for modern herpetofauna and is exceedingly rare in fossil herpetofauna studies.
The overarching goal of this thesis is to advance stable isotope research of reptiles and amphibians. To achieve this, I (1) reviewed the existing literature to identify trends, gaps, and high-priority research directions; (2) generated baseline functional knowledge to improve interpretation of stable isotope results; and (3) contributed original data on the foraging ecology of modern and ancient lizards and niche partitioning within an ancient frog community. My findings demonstrate that fossil frogs can reveal key environmental conditions beyond the conventional climate-niche applications of presence/absence data, tissue enrichments were relatively consistent, and that Podarcis pityusensis has maintained a relatively broad niche for thousands of years. Together, these contributions strengthen the methodological foundation for stable isotope analysis in herpetofauna and expand its potential for both modern ecological and paleoecological research.