Predicting how populations will respond to environmental change is an inherently complex problem often simplified due to the limitations of particular research approaches. For example, conservation genomics studies often lack insight into phenotypic traits important to environmental tolerance, while physiological studies are often limited to individuals from a single population and lack insight into population variation and the capacity for traits to evolve. Forester et al. (2025) combine conservation genomics and physiological ecology to gain important insights into the climate change vulnerability of two cold water stream frogs (Ascaphus montanus and Ascaphus truei). They developed the first annotated reference genome for A. truei and took advantage of a large data set quantifying thermal tolerance across populations of both species from a diversity of thermal environments. The authors first showed evidence for local adaptation to temperature in both species and a genetic basis to critical thermal maximum temperature (CTmax), a common metric to assess thermal tolerance. Importantly, by examining population variation, they were able to conclude that Ascaphus montanus populations appear to exhibit adaptive divergence in CTmax, such that populations have similar vulnerability to future warming. In contrast, Ascaphus truei showed only genomic evidence for local adaptation and no divergence in CTmax. A similar sensitivity to high temperatures across populations means that A. truei populations occupying warmer streams (e.g., low elevation) are closer to their upper tolerance limits and thus more vulnerable to future warming compared to populations occurring in colder streams (e.g., high elevation). The real-world implications of these results mean that management decisions used to mitigate the impacts of future warming on Ascaphus montanus may differ for Ascaphus truei, although both species appear to have high levels of evolutionary potential based on the genomic and physiological data.

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