title: Invasion of the Q2 mitochondrial variant of Mediterranean Bemisia tabaci in southern Italy: possible role of bacterial endosymbionts.
abstract: BACKGROUND
  The whitefly Bemisia tabaci (Gennadius) is a complex of cryptic species, some of which, namely the Mediterranean (MED) and the Middle East-Asia Minor 1 (MEAM1), are highly invasive and injurious crop pests worldwide and able to displace local genotypes. Invasiveness of B. tabaci may depend on the phenotype of inherited bacterial endosymbionts. Here, the B. tabaci genetic diversity variation that has occurred in recent years in southern Italy was examined. Whitefly was genotyped by restriction fragment length polymorphism analysis of polymerase-chain-reaction-amplified fragments (PCR-RFLP) of the COI gene and molecular identification of endosymbionts. Possible factors leading to the observed genetic diversity were examined.
  
  
  RESULTS
  Q1 and Q2 mitochondrial types of MED, the only species found, coexisted in the field, while MEAM1 disappeared. A large spreading of Q2 (70% of individuals) was observed for the first time in Italy. Q2 showed a significant female-biased sex ratio and largely outnumbered Q1 on solanaceous hosts, in greenhouses and on insecticide-treated plants. Q1, with an even sex ratio, slightly prevailed on non-solanaceous hosts, especially on wild and untreated plants. Endosymbiont composition was associated with the mitochondrial type. Hamiltonella and Rickettsia were found at near fixation in Q1 and Q2 respectively; Arsenophonus, Cardinium and Wolbachia were found in both types, although at different frequencies.
  
  
  CONCLUSIONS
  Q2 invasion seems to have been favoured by the agroecological conditions of southern Italy and by the female-biased sex ratio. Endosymbionts may have a role in Q2 invasiveness, acting as sex-ratio manipulators (e.g. Rickettsia) and possibly by benefiting the host fitness.
authors.affiliation: National Research Council, Institute for Plant Protection, Portici, Napoli, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Parrella
authors.forename: Anna Giulia
authors.initials: AG
authors.lastname: Nappo
authors.forename: Elena
authors.initials: E
authors.lastname: Manco
authors.forename: Barbara
authors.initials: B
authors.lastname: Greco
authors.forename: Massimo
authors.initials: M
authors.lastname: Giorgini
mesh_terms: D000818:Animals; D001419:Bacteria / Q000235:genetics* / Q000302:isolation & purification*; D005260:Female; D014644:Genetic Variation; D006430:Hemiptera / Q000235:genetics* / Q000382:microbiology*; D058865:Introduced Species; D007558:Italy; D008297:Male; D008928:Mitochondria / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012744:Sex Ratio; D013559:Symbiosis
keywords: Q1 and Q2 mitochondrial types; Rickettsia; facultative endosymbionts; female-based sex ratio; host plants; reproductive manipulations