From Molecules to Whole Organisms: Insect Responses to Climate Change

Global atmospheric temperatures are rising at accelerated rates, exposing organisms to novel and potentially unsuitable changes in their environment. In order to survive changes in their thermal environments, organisms can employ physiological plasticity on short time scales or species can adapt over evolutionary time. Species may utilize one or both of these strategies to ensure survival; however, if they are incapable of responding to change, they may face extinction. Insect species may be some of the most vulnerable organisms experiencing climate change-induced alterations in their thermal environments because, as ectotherms, temperature influences nearly all of their physiological processes. By characterizing physiological responses to global change, we can begin to understand how organisms are currently responding to climate change and predict how organisms may respond in the future. My research aims to elucidate how insects respond to changes in their thermal environment by examining multiple physiological responses to winter warming in diapausing Pieris rapae butterflies, and the evolution of transcriptomic responses to heat shock in early Drosophila melanogaster embryos. Winter warming caused P. rapae butterflies to have compromised supercooling points, lowered cryoprotectant abundances, shifted metabolomes, more variable metabolic rates, and switches in energy fuel usage. While heat shock caused thermally sensitive early D. melanogaster embryos to exhibit changes in the abundance of thousands of gene transcripts, regardless of the region of origin. But, D. melanogaster embryos with higher thermal tolerance from tropical populations had higher abundance of key transcripts that encode proteins involved in the oxidative stress response. My results suggest that insects endure a broad suite of physiological consequences when the temperature increases. Will these species survive climate change? My work suggests that diapausing P. rapae may be threatened by winter warming, but also shows that some individuals can recover from winter warming. My work also demonstrates that the evolutionary genetic basis of heat tolerance in early D. melanogaster embryos is mediated at the level of the transcriptome, and suggests that D. melanogaster has the potential for adaptation to heat shock temperatures. However, to what extent these species will be challenged by future warming patterns, and if they will continue to evolve and adapt at a rate suitable for survival, needs to be further studied