Wolbachia and cytoplasmic incompatibility in the spider mites Tetranychus urticae and T. turkestani

Abstract

Wolbachia form a group of closely related intracellular Proteobacteria that manipulate reproduction of their arthropod host in various ways. They are widespread in insects, but have not been not looked for in other arthropods except a few isopods and a predatory mite. Recently, Wolbachia were demonstrated to be widespread in mites also. Here, I report that Wolbachia induce cytoplasmic incompatibility in two spider mite species, Tetranychus urticae and T. turkestani, in crosses between infected and uninfected individuals. Uninfected mites were derived from the infected lineage by antibiotic treatment. Similar to other examples of cytoplasmic incompatibility, subsequent crosses between uninfected (cured) female and infected male spider mites were different from all other cross combinations. This suggests that the dynamics and evolution in Wolbachia-mite relationships may share many features with the Wolbachia-insect systems. Interestingly, the incompatible cross showed high F1 zygotic mortality among females, but not among males. This zygotic mortality in the haplodiploid spider mites was in sharp contrast to the phenotypic effects of cytoplasmic incompatibility reported previously in haplodiploid insects. In the latter, cytoplasmic incompatibility results in all male or male-biased offspring because of haploidization of the fertilized egg with little or no zygotic mortality. Possible explanations are low bacterial densities and the different, holokinetic chromosome structure in spider mites.