Bacteria in the genus Rickettsia are intracellular symbionts of disparate groups of organisms. Some Rickettsia strains infect vertebrate animals and plants, where they cause diseases, but most strains are vertically inherited symbionts of invertebrates. In insects Rickettsia symbionts are known to have diverse effects on hosts ranging from influencing host fitness to manipulating reproduction. Here we provide evidence that a Rickettsia symbiont causes thelytokous parthenogenesis (in which mothers produce only daughters from unfertilized eggs) in a parasitoid wasp, Pnigalio soemius (Hymenoptera: Eulophidae). Feeding antibiotics to thelytokous female wasps resulted in production of progeny that were almost all males. Cloning and sequencing of a fragment of the 16S rRNA gene amplified with universal primers, diagnostic PCR screening of symbiont lineages associated with manipulation of reproduction, and fluorescence in situ hybridization (FISH) revealed that Rickettsia is always associated with thelytokous P. soemius and that no other bacteria that manipulate reproduction are present. Molecular analyses and FISH showed that Rickettsia is distributed in the reproductive tissues and is transovarially transmitted from mothers to offspring. Comparison of antibiotic-treated females and untreated females showed that infection had no cost. Phylogenetic analyses of 16S rRNA and gltA gene sequences placed the symbiont of P. soemius in the bellii group and indicated that there have been two separate origins of the parthenogenesis-inducing phenotype in the genus Rickettsia. A possible route for evolution of induction of parthenogenesis in the two distantly related Rickettsia lineages is discussed.The genus Rickettsia contains a group of obligate intracellular symbionts of eukaryotic cells and belongs to the family Rickettsiaceae in the order Rickettsiales of the Alphaproteobacteria (58, 90). Many species have medical importance as they are pathogens of humans and other vertebrates; pathogenic Rickettsia species infect their hosts through blood-feeding arthropods, including lice, fleas, ticks, and mites (51, 80). In addition to Rickettsia species that cause infectious diseases in vertebrates, symbiotic species have been found in disparate groups of organisms, including arthropods, annelids, amoebae, hydrozoa, and plants (53). Rickettsia appears to be especially common in arthropods, having been found in a wide range of taxa in the classes Entognatha

The blue-gum chalcid Leptocybe invasa Fisher & LaSalle (Hymenoptera: Eulophidae) is a gall wasp pest of Eucalyptus species, likely native to Australia. Over the past 15 years it has invaded 39 countries on all continents where eucalypts are grown. The worldwide invasion of the blue gum chalcid was attributed to a single thelytokous morphospecies formally described in 2004. Subsequently, however, males have been recorded in several countries and the sex ratio of field populations has been found to be highly variable in different areas. In order to find an explanation for such sex ratio differences, populations of L. invasa from a broad geographical area were screened for the symbionts currently known as reproductive manipulators, and both wasps and symbionts were genetically characterized using multiple genes. Molecular analyses suggested that L. invasa is in fact a complex of two cryptic species involved in the rapid and efficient spread of the wasp, the first recovered from the Mediterranean region and South America, the latter from China. All screened specimens were infected by endosymbiotic bacteria belonging to the genus Rickettsia. Two closely related Rickettsia strains were found, each infecting one of the two putative cryptic species of L. invasa and associated with different average sex ratios. Rickettsia were found to be localized in the female reproductive tissues and transovarially transmitted, suggesting a possible role of Rickettsia as the causal agent of thelytokous parthenogenesis in L. invasa. Implications for the variation of sex ratio and for the management of L. invasa are discussed.

A new combined molecular and morphological phylogeny of the Eulophidae is presented with special reference to the subfamily Entedoninae. We examined 28S D2–D5 and CO1 gene regions with parsimony and partitioned Bayesian analyses, and examined the impact of a small set of historically recognized morphological characters on combined analyses. Eulophidae was strongly supported as monophyletic only after exclusion of the enigmatic genus Trisecodes. The subfamilies Eulophinae, Entiinae (=Euderinae) and Tetrastichinae were consistently supported as monophyletic, but Entedoninae was monophyletic only in combined analyses. Six contiguous bases in the 3e′ subregion of the 28S D2 rDNA contributed to placement of nominal subgenus of Closterocerus outside Entedoninae. In all cases, Euderomphalini was excluded from Entiinae, and we suggest that it be retained in Entedoninae. Opheliminae n. stat. is raised from tribe to subfamily status. Trisecodes is removed from Entedoninae but retained as incertae sedis in Eulophidae until its family placement can be determined new placement. The genera Neochrysocharisstat. rev. and Asecodesstat. rev. are removed from synonymy with Closterocerus because strong molecular differences corroborate their morphological differences. Closterocerus (Achrysocharis) germanicus is transferred to the genus Chrysonotomyian. comb. based on molecular and morphological characters.