It is often assumed that ecological interactions happen at rapid rates relative to evolutionary change. In this study we examined the development and physiology of an amphibian (Rana sylvatica) from populations found in forested wetlands, and from wetlands that had been cleared by reinvading beaver (Castor canadensis). Embryos from beaver wetlands hatched at lower rates when raised in a shaded, common garden setting compared with embryos from forested wetlands. Larvae from beaver wetlands had higher critical thermal maxima compared with conspecifics from forested wetlands. These patterns suggest that R. sylvatica populations may have diverged rapidly (in less than 36 years) in response to changes in their environment induced by another species. Other agents of thermal change, such as anthropogenic landscape conversion or alteration of global climate, could have analogous impacts on wetland dependent species such as amphibians.