Thermal preference plasticity and fitness of an invasive polyphagous insect in heterogeneous environments

International audienceClimate change has a strong impact on insects, including changes in phenology, distribution area or population extinction. The capacity for behavioral thermoregulation then becomes a crucial trait when the environment is sufficiently heterogeneous to allow individuals to find areas that are always favorable to sub-lethal. Thermal preference (also called selected temperature) is a central trait in behavioral thermoregulation, but to date very few studies have analyzed in depth the plasticity of this trait and the mechanisms (adaptive or not) underlying this plasticity. The study proposed here consists of analyzing this trait in an invasive insect whose invasion success has been dazzling: Drosophila suzukii. This fly has spread widely in Europe, despite having rather low thermal resistance traits compared to other species. Our hypothesis is that the plasticity of the thermal preference allows this fly to constantly make the "right choices" by selecting favorable microclimates during all seasons. This polyphagous fly causes significant economic damage, and its ability to lay and develop in a wide range of fruits (cultivated and wild) must play a role in this success. The thesis consists in determining the interaction between temperature and the resource (identity of the fruit) in the success of Drosophila suzukii. Are there tradeoffs between host (resource) selection and behavioral thermoregulation? The experiments aim to quantify the plasticity of thermal preference as a function of environmental conditions (thermal and trophic). The thesis will identify the adaptive value (fitness) of the thermal preference plasticity in a context of climate change