Multiple Data Demonstrate That Bacteria Regulating Reproduction Could Be Not the Cause for the Thelytoky of Diglyphus wani (Hymenoptera: Eulophidae)

Simple Summary In Hymenoptera, some species have two reproduction modes, that is, arrhenotokous and thelytokous parthenogenesis. Although arrhenotoky is common, the thelytoky is not rare. Thelytoky in Hymenopteran species has several causes and is generally induced by bacteria. Here, we examined a thelytokous Chalcidoidea parasitoid, Diglyphus wani, which was recently reported to be a dominant parasitoid attacking agromyzid leafminers. In this study, we aimed to combine multiple methods to explore whether endosymbionts induce thelytokous D. wani. Our findings revealed that the thelytoky of D. wani was not to be associated with the actual presence of the endosymbionts. Thus, Diglyphus wani is the second reported eulophid parasitoid for which thelytoky is not linked with the presence of endosymbionts. In Hymenoptera parasitoids, the reproductive mode is arrhenotoky, while a few species reproduce by thelytoky. The thelytoky of Hymenoptera parasitoids is generally genetically determined by the parasitoids themselves or induced by bacteria, including Wolbachia, Cardinium, and Rickettsia. Diglyphus wani (Hymenoptera: Eulophidae), a recently reported thelytokous species is a main parasitoid attacking agromyzid leafminers. To assess whether endosymbionts induce thelytoky in D. wani, we performed universal PCR detection and sequenced the V3-V4 region of 16S ribosomal RNA gene. In addition, bacteria were removed through high-temperature and antibiotic treatments, and the localized bacteria were detected using FISH. Based on general PCR detection, Wolbachia, Cardinium, Rickettsia, Arsenophonus, Spiroplasma, and Microsporidia were absent in laboratory and field individuals of thelytokous D. wani. Furthermore, 16S rRNA gene sequencing revealed that the dominant endosymbionts in thelytokous D. wani were not reproductive manipulators. High-temperature and antibiotic treatment for five consecutive generations cannot reverse the thelytokous pattern of D. wani, and no male offspring were produced. Moreover, no bacterial spots were found in the ovaries of D. wani. Thus, it is considered that the thelytoky of D. wani does not result in the presence of endosymbionts. This species is thus the second reported eulophid parasitoid whose thelytoky appears not to be associated with endosymbionts.

Automated summary

This study finds that the thelytoky of Diglyphus wani is not linked with the presence of endosymbionts.