Abstract:
Facultative bacterial endosymbionts are associated with many arthropods and are primarily
transmitted vertically from mother to offspring. However, phylogenetic affiliations suggest
that horizontal transmission must also occur. Such horizontal transfer can have important
biological and agricultural consequences when endosymbionts increase host fitness. So far
horizontal transmission is considered rare and has been difficult to document. Here, we use
fluorescence in situ hybridization (FISH) and multi locus sequence typing (MLST) to reveal
a potentially common pathway of horizontal transmission of endosymbionts via parasitoids
of insects. We illustrate that the mouthparts and ovipositors of an aphelinid parasitoid become
contaminated with Wolbachia when this wasp feeds on or probes Wolbachia-infected
Bemisia tabaci AsiaII7, and non-lethal probing of uninfected B. tabaci AsiaII7 nymphs by
parasitoids carrying Wolbachia resulted in newly and stably infected B. tabaci matrilines.
After they were exposed to infected whitefly, the parasitoids were able to transmit Wolbachia
efficiently for the following 48 h. Whitefly infected with Wolbachia by parasitoids had increased
survival and reduced development times. Overall, our study provides evidence for
the horizontal transmission of Wolbachia between insect hosts by parasitic wasps, and the
enhanced survival and reproductive abilities of insect hosts may adversely affect biological
control programs.
