Embryo development and global change: how do reptile embryos respond to ecologically relevant thermal stress?
Two components of global change, climate change and urbanization, contribute to increased ambient temperatures that cause heat stress or mortality in animals. Many animals can respond to harmful temperatures behaviorally; however, embryos of ectotherms which develop inside eggs in the ground and receive little or no parental care cannot respond this way. This early life stage is more vulnerable to harmful temperatures, yet, the effects of ecologically relevant thermal stress on these embryos has received little attention. We measured ground temperatures in an urban landscape where lizards (Anolis sagrei and Anolis cristatellus) nest and exposed eggs to extreme nest temperatures in the lab. We determined the critical thermal maximum for embryos of each species and assessed how thermal tolerance might change through development. Our results show that the thermal tolerance of reptile embryos can differ widely among closely related species, and thermal tolerance can change through development.