Obligate thelytoky in oribatid mites: No evidence for Wolbachia inducement

The wide distribution of obligate thelytoky in oribatid mites (Acari: Oribatida) raises the question of the mechanisms that allowed genetic diversity to be maintained or even promoted in these taxa. We tested whether or not endosymbiotic bacteria Wolbachia are associated with thelytoky in eight species of oribatid mites (as it is for most thelytokous parasitic Hymenoptera studied so far) by using a polymerase chain reaction assay. Our negative results in the selective amplification of Wolbachia DNA suggest that these bacteria are not responsible for the thelytokous mode of reproduction of oribatid mites. On the basis of known or suspected cytogenetic mechanisms in oribatid mites (automictic thelytoky, inverted meiosis), we discuss an alternative hypothesis for the inducement of thelytoky, and its relevance to the observed diversification of thelytokous oribatid mites over evolutionary time.