Local divergence of thermal reaction norms among amphibian populations is affected by pond temperature variation

While temperature variation is known to cause large-scale adaptive divergence, its potential role as a selective factor over microgeographic scales is less well understood. Here, we investigated how variation in breeding pond temperature affects divergence in multiple physiological (thermal performance curve (TPC) and critical thermal maximum (CTmax)) and life history (thermal developmental reaction norms (TDRN)) traits in a network of Rana arvalis populations. The results supported adaptive responses to face two main constraints limiting the evolution of thermal adaptation. First, we found support for the faster-slower model, indicating an adaptive response to compensate for the thermodynamic constraint of low temperatures in colder environments. Secondly, we found evidence for the generalist-specialist trade-off with populations from colder and less thermally variable environments exhibiting a specialist phenotype performing at higher rates but over a narrower range of temperatures. B...