A newly discovered bacterium associated with parthenogenesis and a change in host selection behavior in parasitoid wasps

doi:10.1073/pnas.221467498

A newly discovered bacterium associated with parthenogenesis and a change in host selection behavior in parasitoid wasps

^†Department of Plant Sciences, 303 Forbes Building, University of Arizona, Tucson, AZ 85721; ^‡Department of Organismal Biology and Anatomy, 1027 East 57th Street, University of Chicago, Chicago, IL 60637; ^§Department of Entomology, 410 Forbes Building, University of Arizona, Tucson, AZ 85721; and ^¶Department of Cell Biology and Anatomy, P.O. Box 245044, University of Arizona, Tucson, AZ 85721

Communicated by Margaret G. Kidwell, University of Arizona, Tucson, AZ (received for review February 6, 2001)

Abstract

The symbiotic bacterium Wolbachia pipientis has been considered unique in its ability to cause multiple reproductive anomalies in its arthropod hosts. Here we report that an undescribed bacterium is vertically transmitted and associated with thelytokous parthenogenetic reproduction in Encarsia, a genus of parasitoid wasps. Although Wolbachia was found in only one of seven parthenogenetic Encarsia populations examined, the “Encarsia bacterium” (EB) was found in the other six. Among seven sexually reproducing populations screened, EB was present in one, and none harbored Wolbachia. Antibiotic treatment did not induce male production in Encarsia pergandiella but changed the oviposition behavior of females. Cured females accepted one host type at the same rate as control females but parasitized significantly fewer of the other host type. Phylogenetic analysis based on the 16S rDNA gene sequence places the EB in a unique clade within the Cytophaga-Flexibacter-Bacteroid group and shows EB is unrelated to the Proteobacteria, where Wolbachia and most other insect symbionts are found. These results imply evolution of the induction of parthenogenesis in a lineage other than Wolbachia. Importantly, these results also suggest that EB may modify the behavior of its wasp carrier in a way that enhances its transmission.

Footnotes

↵ ‖ To whom reprint requests should be addressed. E-mail: mhunter{at}ag.arizona.edu.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database [accession nos. AY026336 (E. berlesei), AY026333 (E. citrina), AY026334 (E. hispida), AF319783 (E. pergandiella, Brazil), and AY026335 (E. pergandiella, Texas)].
Abbreviations:

EB,

Encarsia bacterium;

CFB,

Cytophaga-Flexibacter-Bacteroid;

PI,

parthenogenesis induction