What allows organisms to adapt to some habitats but not others? Uncovering the factors that structure species’ ecological limits is central to understanding the formation of biological diversity and to predicting responses on our changing planet. Although much research on ecological limits has assessed the physiological tolerances that permit growth and survival, existing in a habitat also requires that species successfully mate and reproduce. Our lab studies how species’ ecological limits and responses to global change are shaped by the physiology of mating and reproduction.