Wolbachia symbiosis in the agriculturally-important predatory mite Metaseiulus occidentalis

This study focused on detecting, describing, and evaluating the biological effects of Wolbachia endosymbionts in the predatory mite Metaseiulus occidentalis (Nesbitt) (Acari: Phytoseiidae). Wolbachia were found in adults and eggs of M. occidentalis using Wolbachia-specific polymerase chain reaction (PCR) primers which amplify the 16S ribosomal RNA and ftsZ genes. Wolbachia also were found in their prey, the two spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae). Wolbachia DNA from the two mite species was sequenced and compared. Parsimony analysis indicated the mite Wolbachia sequences were very similar to one another and to Wolbachia from insects. Wolbachia DNA could be transiently detected in the uninfected predatory mite Amblyseius reductus Wainstein (Acari: Phytoseiidae) after feeding on infected spider mites, indicating the infection status of any predatory arthropod's diet should be considered before using the PCR to detect Wolbachia.;In insects, Wolbachia causes nonreciprocal reproductive incompatibilities in crosses between infected males and uninfected females; the reciprocal crosses are normal. Genetically similar populations of M. occidentalis differing in the presence of Wolbachia (due to heat-curing of one population) were crossed to assess the effects of the symbiont. Wolbachia did induce non-reciprocal incompatibilities in this parahaploid mite, evidenced by significantly fewer viable eggs, higher proportions of egg shriveling as compared to the reciprocal and control crosses, and no or few female progeny.;To determine whether the proportion of Wolbachia-infected M. occidentalis in a polymorphic population would increase over time (because infected females can reproduce with both infected and uninfected males), three M. occidentalis populations were initiated with 10% infected and 90% cured mites and monitored for 22 generations. Wolbachia infection did not spread rapidly through the populations. Imperfect transmission rates and fitness costs were detected, which may prevent the rapid spread of Wolbachia. This suggests Wolbachia would not be useful as a "drive mechanism" for inserting useful genes into field populations of M. occidentalis.