Wolbachia has no effect on thermal preference at different life-stages in highly inbred Drosophila melanogaster

Temperature fluctuations are challenging for ectotherms which are not able to regulate body temperature by physiological means and thus have to adjust their thermal environment via behavior. However, little is yet known about whether microbial symbionts influence thermal preference (Tp) in ectotherms by modulating their physiology. Several recent studies have demonstrated substantial effects of Wolbachia infections on host Tp in different Drosophila species. These data indicate that the direction and strength of thermal preference variation is strongly depend on host and symbiont genotypes and highly variable among studies. By employing highly controlled experiments, we investigated the impact of several environmental factors including humidity, food quality, light exposure, and experimental setup that may influence Tp measurements in adult flies. Additionally, we assessed the effects of Wolbachia infection on Tp of Drosophila at different developmental stages, which has not been done before. We find no effects of Wolbachia on host Tp at any life stage. Instead, we show that environmental variation has a substantial influence on Tp measurements which demonstrates the necessity of careful experimental design and cautious interpretations of Tp measurements together with a thorough description of the methods and equipment used to conduct behavioral studies. ### Competing Interest Statement The authors have declared no competing interest.