Conditional effects of <i>Cardinium</i> on microbiota in an invasive whitefly under different ecological factors

<i>Cardinium</i>, a vital symbiont in <i>Bemisia tabaci</i> Mediterranean (MED), can influence the microbiota in <i>B. tabaci</i> MED under high temperatures. However, the effects of <i>Cardinium</i> infection on the microbiota in <i>B. tabaci</i> MED with different genetic backgrounds under different ecological factors still remain poorly understood. In this study, based on full-length 16S rRNA gene sequencing and quantitative PCR (qPCR) experiments, the effects of <i>Cardinium</i> infection on the microbiota in two <i>B. tabaci</i> MED geographical populations with different genetic backgrounds were determined with particular attention to ecological factors such as high-temperature treatment and host-plant switching. Results indicated that high temperature treatment and host-plant switching affected the symbiont titer, microbiota diversity, and function differently in the two populations, highlighting the genetic background. The present study also revealed that the increase of <i>Cardinium</i> titer would significantly change the response of the microbiota function of the <i>Cardinium</i>-infected line compared to the uninfected line, while the decrease and immutability of <i>Cardinium</i> titer would not, which indicates that the <i>Cardinium</i> titer may be closely associated with the microbiota function in whitefly. Overall, the genetic background of whiteflies influences microbiota response under high temperatures and host-plant changes, and <i>Cardinium</i> titer significantly impacts microbiota function. These findings enhance understanding of the complex relationships among symbionts, microbiota, and host insects.IMPORTANCEThis study sheds light on how genetic differences in <i>Bemisia tabaci</i> Mediterranean (MED) populations influence their microbiota's response to environmental stressors like high temperatures and host-plant changes. By focusing on the role of <i>Cardinium</i>-a key symbiont-the research reveals its significant impact on microbiota diversity and function, particularly when its titer increases. The findings emphasize the interplay between genetic background, symbiont levels, and microbiota, advancing our understanding of the ecological adaptability of these insects. This knowledge is vital for developing better pest management strategies and predicting responses to environmental changes.