Stress Responses and Candidate Gene Expression Investigated Across Species and Ecosystems in the Field

Terrestrial arthropods are continuously exposed to temperature changes at multiple spatiotemporal scales. Because of the tight link between arthropod physiology and the environment, they must anticipate and respond to these changes within and across generations to maintain high fitness. Hence, survival and reproductive success to temperature variation and global warming depend on phenotypic plasticity in physiological, behavioral and morphological responses, and on evolutionary adaptation. Currently, knowledge on species ability to respond and adapt to environmental stress is based on studies conducted under laboratory condition using model organisms. These estimates have little external validity and often conclusions based on laboratory studies does not match fitness in nature.

This thesis investigates the extent to which phenotypic plasticity occurs in species in their natural environments with a focus on the temporal scale that the species respond to temperature fluctuations, the climatic predictors of plastic changes, and the evolutionary adaptation to environments characterized by different thermal variabilities. This is supplemented with a mechanistic understanding of the underlying molecular basis behind field-based plastic responses. With these endeavors, this thesis provides an ecological context for phenotypic plasticity and evolutionary adaptation.