Negative evidence of parthenogenesis induction byWolbachiain a gallwasp species,Dryocosmus kuriphilus

Abstract

AbstractThe alpha‐proteobacteria of the genusWolbachiais a widespread group of maternally inherited endosymbionts of arthropod and nematode hosts.Wolbachiainfection induces a range of host phenotypes, including cytoplasmic incompatibility, male killing, feminization, and induction of thelytokous parthenogenesis. Heterogony (cyclical parthenogenesis) is a remarkable characteristic of oak gallwasps, Cynipini, the largest tribe of the Cynipidae. A few species of Cynipini are exceptional in that they are univoltine and exhibit thelytokous parthenogenesis, probably because they lost the arrhenotokous generation of their heterogonic ancestor species due toWolbachiainfection. In this study, the presence ofWolbachiawas detected using polymerase chain reaction primers for thewspgenes in a thelytokous parthenogenetic species [Dryocosmus kuriphilus(Yasumatsu)] (Hymenoptera: Cynipidae: Cynipini). Approximately 29.8 and 87.1% of adults of the Zhuzhou and Fuzhou strains, respectively, were infected withWolbachiawhile all females of the remaining four strains collected from other localities in China wereWolbachiafree. The length of thewspfragment of Zhuzhou and Fuzhou strains was found to be 573 and 561 bp, respectively. The nucleotide sequence of the bacterialwspfragment indicated that the endosymbiotic bacteria of the Zhuzhou and Fuzhou strains are members of supergroup A, but belong to different clades; they probably originated from two independent infection events. In conclusion, thelytokous parthenogenesis ofD. kuriphilusis not caused byWolbachiainfection and the deletion of the arrhenotokous generation is thus not associated with such an infection.