Understanding Growth and Developmental Responses of Ectotherms to Fluctuating Environments: Beyond Performance Curves

Understanding how organisms respond and adapt to fluctuating environments is a major challenge for biologists. The responses of an organism to current environmental conditions can depend on conditions it experienced in the past, due to either stress (negative effects) or acclimation (positive effects). Biologists currently lack a framework for understanding and quantifying those effects: the goal of this project is to develop and test such a framework, using the growth responses of a model system, the Tobacco Hornworm (Manduca sexta), to variable temperatures. The research integrates physiological experiments, genomics analyses and mathematical models to predict the consequences of stress and acclimation on growth, development and survival, and to test these predictions for unpredictable temperature conditions. This new framework will allow a quantitative understanding of responses of Tobacco Hornworms and other agricultural pests to variability in weather; the general framework should be applicable to most other 'cold-blooded' animals. The project provides research training and experience for undergraduate and graduate students, and develops a new citizen science program for monitoring butterflies and moths in the piedmont region of North Carolina.

During the course of a single lifespan, terrestrial ectotherms often experience wide variation in temperature and other environmental factors. An individual's performance can vary with temperature, represented as a thermal performance curve (TPC), and TPCs are the basis for many models predicting organismal responses to fluctuating temperatures. However, many ectotherms exhibit time-dependent effects, including stress responses and acclimation, where the duration and order of prior temperature exposure affect organismal performance; these effects are ignored in the standard TPC approach. The studies proposed here develop and test a new framework for incorporating time-dependent effects into models of ectotherm performance, using growth rate of Manduca sexta larvae in fluctuating temperatures as a model system. The proposed studies integrate physiological experiments, functional genomic and protein analyses, and mathematical models to develop and parameterize a systems modeling framework for stress and acclimation responses, and test predictions from this model in response to stochastic variation in diurnal temperature fluctuations. The proposed research will provide the bases for a new conceptual and modeling framework for understanding and predicting the effects of variation in temperature and climate on growth and fitness of ectotherms. The project provides research training and experience for undergraduate and graduate students, and develops a new citizen science program for monitoring butterflies and moths in the piedmont region of North Carolina.