title: Population structure of Wolbachia and cytoplasmic introgression in a complex of mosquito species.
abstract: BACKGROUND
  The maternally inherited bacterium Wolbachia often acts as a subtle parasite that manipulates insect reproduction, resulting potentially in reproductive isolation between host populations. Whilst distinct Wolbachia strains are documented in a group of evolutionarily closely related mosquitoes known as the Culex pipiens complex, their impact on mosquito population genetics remains unclear. To this aim, we developed a PCR-RFLP test that discriminates the five known Wolbachia groups found in this host complex. We further examined the Wolbachia genetic diversity, the variability in the coinherited host mitochondria and their partitioning among members of the Cx. pipiens complex, in order to assess the impact of Wolbachia on host population structure.
  
  
  RESULTS
  There was a strong association between Wolbachia and mitochondrial haplotypes indicating a stable co-transmission in mosquito populations. Despite evidence that members of the Cx. pipiens complex are genetically distinct on the basis of nuclear DNA, the association of Wolbachia and mtDNA with members of the Cx. pipiens complex were limited. The Wolbachia wPip-I group, by far the most common, was associated with divergent Cx. pipiens members, including Cx. quinquefasciatus, Cx. pipiens pipiens form pipiens and Cx. pipiens pipiens form molestus. Four other wPip groups were also found in mosquito populations and all were shared between diverse Cx. pipiens members.
  
  
  CONCLUSIONS
  This data overall supports the hypothesis that wPip infections, and their allied mitochondria, are associated with regular transfers between Cx. pipiens members rather than specific host associations. Overall, this is suggestive of a recent and likely ongoing cytoplasmic introgression through hybridization events across the Cx. pipiens complex.
authors.affiliation: Institut des Sciences de l'Evolution, UMR5554 CNRS, Université Montpellier 2, 34095 Montpellier cedex 05, France. olivier.duron@univ-montp2.fr.
authors.forename: Emilie
authors.initials: E
authors.lastname: Dumas
authors.forename: Célestine M
authors.initials: CM
authors.lastname: Atyame
authors.forename: Pascal
authors.initials: P
authors.lastname: Milesi
authors.forename: Dina M
authors.initials: DM
authors.lastname: Fonseca
authors.forename: Elena V
authors.initials: EV
authors.lastname: Shaikevich
authors.forename: Sandra
authors.initials: S
authors.lastname: Unal
authors.forename: Patrick
authors.initials: P
authors.lastname: Makoundou
authors.forename: Mylène
authors.initials: M
authors.lastname: Weill
authors.forename: Olivier
authors.initials: O
authors.lastname: Duron
mesh_terms: D000818:Animals; D005075:Biological Evolution; D003465:Culex / Q000145:classification / Q000382:microbiology*; D004272:DNA, Mitochondrial / Q000235:genetics; D014644:Genetic Variation; D006239:Haplotypes; D016133:Polymerase Chain Reaction; D020577:Wolbachia / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D004272:DNA, Mitochondrial