title: Genetic Diversity of the Invasive Gall Wasp Leptocybe invasa (Hymenoptera: Eulophidae) and of its Rickettsia Endosymbiont, and Associated Sex-Ratio Differences.
abstract: 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.
authors.affiliation: Istituto per la Protezione Sostenibile delle Piante, Consiglio Nazionale delle Ricerche, Portici (NA), Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Nugnes
authors.affiliation: Istituto per la Protezione Sostenibile delle Piante, Consiglio Nazionale delle Ricerche, Portici (NA), Italy; Department of Entomology, The University of Arizona, Tucson, Arizona, the United States of America.
authors.forename: Marco
authors.initials: M
authors.lastname: Gebiola
authors.affiliation: Istituto per la Protezione Sostenibile delle Piante, Consiglio Nazionale delle Ricerche, Portici (NA), Italy.
authors.forename: Maurilia Maria
authors.initials: MM
authors.lastname: Monti
authors.affiliation: Istituto per la Protezione Sostenibile delle Piante, Consiglio Nazionale delle Ricerche, Portici (NA), Italy.
authors.forename: Liberata
authors.initials: L
authors.lastname: Gualtieri
authors.affiliation: Istituto per la Protezione Sostenibile delle Piante, Consiglio Nazionale delle Ricerche, Portici (NA), Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Giorgini
authors.affiliation: Department of Plant Protection, College of Agriculture, Jiangxi Agricultural University, Nanchang, Jiangxi Province, China.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Wang
authors.affiliation: Istituto per la Protezione Sostenibile delle Piante, Consiglio Nazionale delle Ricerche, Portici (NA), Italy.
authors.forename: Umberto
authors.initials: U
authors.lastname: Bernardo
mesh_terms: D000818:Animals; D001315:Australia; D002681:China; D005052:Eucalyptus / Q000469:parasitology; D005260:Female; D014644:Genetic Variation; D008297:Male; D010053:Ovary / Q000382:microbiology*; D010312:Parthenogenesis / Q000235:genetics; D010802:Phylogeny; D058974:Phylogeography; D012281:Rickettsia / Q000145:classification / Q000235:genetics*; D017422:Sequence Analysis, DNA; D012744:Sex Ratio; D013020:South America; D013559:Symbiosis; D014863:Wasps / Q000145:classification* / Q000235:genetics* / Q000382:microbiology / Q000472:pathogenicity