Plastic shifts in thermal preference and thermoregulation strategy across ontogeny in an invasive fly

Gwenaëlle Deconninck , Vincent Foray, Sylvain Pincebourde

Behavioural thermoregulation allows ectotherms to escape extreme or seek optimal temperatures. Its precision can impact survival and fitness under changing conditions and its plasticity can be an adaptive strategy when the plasticity of thermal limits is insufficient to buffer against warming. We explore the developmental and intergenerational plasticity of behavioural thermoregulation strategies using the invasive fly Drosophila suzukii, including Wolbachia-infected individuals. We measured the plasticity of its thermal preference (Tp) and used its mean (thermal need) and variance (thermoregulation precision) to assess thermoregulation strategies. Typically, mean Tp increased with developmental temperature as well as the precision in temperature selection. Tp differed between life stages (higher in larvae and females than in males), reflecting different thermal needs. Wolbachia infection was associated with a reduction of Tp in adults but an increase in larvae, associated with a shift of the thermoregulation strategy with higher precision at intermediate Tp. Modulation of Tp may represent a mechanism for coping with changing or novel environmental conditions, opening new perspectives as to whether plasticity in Tp is adaptive under natural conditions, whether such plasticity facilitates colonisation or persistence during range expansion, and whether Tp plasticity itself evolves during range expansion.