Microbial diversity and cytoplasmic incompatibility in Tetranychus urticae Spanish populations.

The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is an important citrus pest worldwide. Global populations of T. urticae harbour Wolbachia and other bacterial species, some of which are considered endosymbionts. The genus Wolbachia encompasses strict intracellular bacteria that cause several types of reproductive distortions in their hosts, such as male feminization, thelytokous parthenogenesis, cytoplasmic incompatibility, or male killing. The presence of different Wolbachia strains can affect the mite's reproductive parameters, which can have important implications for its management. In this study, we explored the microbiota composition of a T. urticae Spanish population and its effect on reproduction after antibiotic treatment. Firstly, we conducted a microbiota characterization using 16S deep sequencing. In a second step, we evaluated reproductive parameters through different crosses between treated and untreated mites (T- and U- lines, respectively). Following antibiotic treatment, the marked reduction in Wolbachia dominance revealed a more even bacterial community composed of several previously low-abundance taxa. This mite microbiota was hidden by the great contribution of Wolbachia to the total number of OTUs. The antibiotic treatment unveiled the presence of other reproductive distorter bacterial species not previously identified in surveys of Spanish mite populations with species-specific primers. We determined that the tetracycline treatment primarily removed Wolbachia from the mite microbiota. The results from the crosses, which showed an altered offspring sex ratio, unveiled an induced cytoplasmic incompatibility (CI) between treated and untreated lines. Our results identify Wolbachia as the most likely endosymbiont associated with the observed cytoplasmic incompatibility.