Due to their dependence on environmental temperatures, ectothermic animals are likely to be particularly sensitive to global climate change. Accurate prediction of ectotherm population responses to climate change requires a mechanistic understanding of effects of increased temperatures on survival and reproduction. Despite organismal development through distinct life stages that may differ in sensitivity to temperature, most studies measure effects on a single life stage. In collaboration with land managers at the US Army base at Fort Bragg, North Carolina, we used a combination of greenhouse and field experiments to measure the effects of temperature increases on fecundity and survival at all life stages of the multivoltine butterfly Satyrodes appalachia. In order to predict temperature effects on population growth, we built a simple model using our experiment results and temperatures projected for our study location through 2099 under the RCP8.5 emissions scenario.
Results/Conclusions
We found that maximum temperature experienced by individuals was the most important temperature variable across life stages explaining changes in vital rates with temperature. Our model indicated that predator-free growth rates decreased with increasing temperatures, and that populations shifted from growing to shrinking at increases of approximately 4 degrees Celsius. A sensitivity analysis revealed that population growth was most sensitive to larval survival during the winter, which was in turn negatively affected by increased temperatures. Our results suggest temperature thresholds for the most sensitive life stages beyond which populations will decline. Our findings demonstrate the need for conservation strategies for ectotherms that target particularly vulnerable life stages.