Flash Drought and Heat Waves Influence Embryonic Development and Offspring Size in an Oviparous Ectotherm

AbstractAnthropogenic climate change is driving an increase in climate extremes, including concurrent drought and heat wave events. To understand the ecological consequences of these events, research is needed to identify their separate and compound effects on organisms across life stages. Oviparous species are particularly vulnerable to environmental stress at the embryonic stage, as embryos are relatively unprotected from hydric and thermal extremes. The embryonic environment can substantially shape offspring physiology and fitness. However, the developmental impacts of extreme climate events, including downstream effects on offspring survival in the field, are not well described. In this study, we investigated the independent and interactive effects of flash drought and heat waves during embryonic development in an oviparous vertebrate model, the painted turtle (Chrysemys picta). In a fully factorial experiment, we imposed simulated flash drought and heat wave events and examined the effects on egg mass, incubation time, and offspring body size. After turtles overwintered in the laboratory, we conducted a release experiment in the field to measure early-life survival in an ecologically relevant context. We found that flash drought and heat wave events interactively influenced egg mass during late embryonic development and independently reduced incubation time and postoverwintering body mass. In addition, smaller individuals had a lower probability of survival in the field. Our results suggest that oviparous species will face negative impacts on embryonic development and early-life traits as compound drought and heat wave events become more frequent and severe.