Unidirectional cytoplasmic incompatibility crossing pattern. White circles represent uninfected individuals and black circles represent Wolbachia infected individuals. Crosses between the same infection type produces viable offspring. Cytoplasmic incompatibility occurs when uninfected females mate with Wolbachia infected males, resulting in reduced numbers of viable offspring. As a result, infected females have an effective mating advantage over uninfected females.
Crain et al. BMC Evolutionary Biology 2011 11:290 doi:10.1186/1471-2148-11-290