Climate Factors and Wolbachia Infection Frequencies in Natural Populations of Drosophila melanogaster

The endosymbiotic bacteria Wolbachia are widespread in natural populations of Drosophila melanogaster , which is a cosmopolitan and synanthropic species. Various aspects of Wolbachia infection are studied in many arthropod species, including fruit flies. However, the influence of climatic factors on the level of Wolbachia infection in natural populations of fruit flies has not been studied in detail. The influence of mean temperature, precipitation, and potential evaporation was investigated on Wolbachia infection rates in ten D. melanogaster populations (collected in Europe) and newly obtained estimates were combined with the data from other studies for different continents and for different climatic zones (280 populations, 10 806 isofemale lines). The effect of climatic factors on the infection frequency was revealed. The highest infection rates are observed in the mean annual temperature range of 20–25°C, which corresponds to fly rearing conditions in the laboratory. The clinal distribution of Wolbachia infection rates in the Eurasian fruit fly populations was described. Logistic regression models showed that climatic factors have a stronger impact on bacterial infection rates within climatic zones rather than continents.