Conclusions
The combination of warming temperatures, extreme events and species redistributions has the potential to fundamentally change marine ecosystems in the Anthropocene. Identifying general principles, developing models and testing predictions about how these impacts will unfold across species distributions is critical to anticipate and adaptively manage ecosystems over coming decades. Here we demonstrate that cool, central and warm-edge populations of seagrass differ in their response to temperature, however these responses are not necessarily linear or conform to a-priori expectations. Moreover, the highly selective effects of warm-affiliated herbivores on cool-edge populations, highlight how species redistributions and species interactions can have unexpected and consequential effects on ecological performance under climate change. Our findings make a strong case for ongoing empirical comparisons of thermal performance for functionally important species and highlight the complexity of inferring thermal sensitivity from a single location. In doing so these findings provide hope for greater resilience to warming in Mediterranean seagrasses than previously recognised.