Embryonic temperature shapes morphology, physiology, and survival across life stages for an ectotherm threatened by global change

Climate change and urbanization expose organisms to novel thermal regimes. These changes are particularly impactful for embryonic development of ectotherms due to a lack of parental care, thermal sensitivity of development, and inability to behaviorally thermoregulate. Although the effects of shifting thermal regimes have been studied extensively using a few vertebrate models, little is known about impacts on species with multiple, distinct life stages such as amphibians. We measured nest temperatures of the Streamside Salamander (Ambystoma barbouri) in both disturbed and undisturbed habitats to determine how urbanization affects embryonic temperature. We incubated eggs across a range of temperatures to understand the effects of temperature on survival and larval and juvenile phenotypes. Resultant larvae and metamorphs were maintained in a common garden to isolate the effects of embryonic temperature, illuminating the effect of nest temperature on each life stage (egg, larvae, juvenile). Maximum nest temperatures were warmer in disturbed than undisturbed sites. Warmer incubation temperatures enhanced developmental rate but decreased survival and body size. These effects persisted into larval and metamorph stages, demonstrating that the effects of embryonic temperature persist across life stages. Our results illustrate the need for a deeper understanding of the long-term effects of nest temperature on ectotherms. Moreover, this work indicates that studies which use egg survival and hatchling phenotypes alone to forecast species responses to global change are conservative, and future work must incorporate the full life cycle.