No evidence for the evolution of mating behavior in spider mites due to Wolbachia-induced cytoplasmic incompatibility

Arthropods are often infected with Wolbachia inducing cytoplasmic incompatibility (CI), whereby crosses between uninfected females and infected males yield unviable fertilized offspring. Although uninfected females benefit from avoiding mating with Wolbachia-infected males, this behavior is not always present in host populations and its evolution may hinge upon various factors. Here, we used spider mites to test whether CI could select for mate preference in uninfected females in absence of kin recognition. We found that uninfected females from several field-derived populations showed no preference for infected or uninfected males, nor evolved a preference after being exposed to CI for 12-15 generations by maintaining uninfected females with both infected and uninfected males (i.e., stable "infection polymorphism"). This suggests that Wolbachia-mediated mate choice evolution may require very specific conditions in spider mites. However, after experimental evolution, the copulation duration of Wolbachia-infected control males was significantly higher than that of uninfected control males, but not than that of uninfected males from the "infection polymorphism" regime. This result illustrates how gene flow may oppose Wolbachia-driven divergence between infected and uninfected hosts in natural populations.