Abstract
Wolbachia are widely distributed bacterial endosymbionts of arthropods and nematodes that can alter the reproductive behavior of host species to their own advantage. Cytoplasmic incompatibility (CI) is a commonly induced phenotype in hosts that is expressed in embryonic death when the sperm of an infected male fertilizes the egg of an uninfected female. The reproductive advantage of infected females over uninfected ones facilitates the spread of the endosymbiont. The maternal transmission of Wolbachia usually results in a strong linkage between infection types and host’s mitochondrial haplotypes. Rhagoletis cerasi is a model organism for studying Wolbachia in natural populations as it harbors several different Wolbachia strains. Confined to south-central Europe, the strain wCer2 induces strong unidirectional CI and has characterized transition zones, where wCer2 is spreading into uninfected populations. Studies of populations from transition zones may therefore provide valuable insight into the spread dynamics of Wolbachia in natural populations. Here we focus on two wCer2 transition zones, one in the Czech Republic and the other in Hungary. A PCR-based Wolbachia screening and a screening of the associated mitochondrial haplotypes was conducted. In both transects, we report a gradient depicting high to low infection frequencies of wCer2. Potential effects of Wolbachia on the genetic structure of R. cerasi will be discussed.