Environments with a high probability of incompatible crosses do not select for mate avoidance in spider mites

Abstract

AbstractArthropods are often infected withWolbachiainducing cytoplasmic incompatibility (CI), whereby crosses between uninfected females and infected males yield unviable fertilized offspring. Although uninfected females benefit from avoiding mating withWolbachia-infected males, this behaviour is not present in all host species. Here we measured the prevalence of this behaviour across populations of the spider miteTetranychus urticae. Females from five populations originally fully infected withWolbachiashowed no preference, possibly because they did not face the choice between compatible and incompatible mates in their environment. Hence, to determine whether this behaviour could be selected in populations with intermediateWolbachiainfection frequency, we performed 15 generations of experimental evolution of spider-mite populations under i) fullWolbachiainfection, ii) no infection, or iii) mixed infection. In the latter selection regime, where uninfected females were exposed to infected and uninfected males at every generation, mating duration increased relative to the uninfected regime, suggesting the presence of genetic variation for mating traits. However, mate choice did not evolve. Together, these results show that CI-inducingWolbachiaalone does not necessarily lead to the evolution of pre-copulatory strategies in uninfected hosts, even at intermediate infection frequency.