title: Endosymbiont phylogenesis in the dryophthoridae weevils: evidence for bacterial replacement.
abstract: Intracellular symbiosis is widespread in the insect world where it plays an important role in evolution and adaptation. The weevil family Dryophthoridae (Curculionoidea) is of particular interest in intracellular symbiosis evolution with regard to the great economical and ecological features of these invasive insects, and the potential for comparative studies across a wide range of host plants and environments. Here, we have analyzed the intracellular symbiotic bacteria of 19 Dryophthoridae species collected worldwide, representing a wide range of plant species and tissues. All except one (Sitophilus linearis) harbor symbiotic bacteria within specialized cells (the bacteriocytes) assembled as an organ, the bacteriome. Phylogenetic analysis of the 16S rDNA gene sequence of the Dryophthoridae endosymbionts revealed three endosymbiotic clades belonging to gamma3-Proteobacteria and characterized by different GC contents and evolutionary rate. The genus name Candidatus Nardonella was proposed for the ancestral clade infesting Dryophthoridae 100 MYA and represented by five of nine bacterial genera studied. For this clade showing low GC content (40.5% GC) and high evolutionary rate (0.128 substitutions/site per 100 Myr), a single infection and subsequent cospeciation of the host and the endosymbionts was observed. In the two other insect lineage endosymbionts, with relatively high GC content (53.4% and 53.8% GC), competition with ancestral pathogenic bacteria might have occurred, leading to endosymbiont replacement in present-day last insects.
authors.affiliation: Laboratoire de Biologie Fonctionnelle Insectes et Interactions, UMR INRA/INSA de Lyon, Villeurbanne, France.
authors.forename: Cédric
authors.initials: C
authors.lastname: Lefèvre
authors.forename: Hubert
authors.initials: H
authors.lastname: Charles
authors.forename: Agnès
authors.initials: A
authors.lastname: Vallier
authors.forename: Bernard
authors.initials: B
authors.lastname: Delobel
authors.forename: Brian
authors.initials: B
authors.lastname: Farrell
authors.forename: Abdelaziz
authors.initials: A
authors.lastname: Heddi
mesh_terms: D000818:Animals; D001482:Base Composition; D001483:Base Sequence; D017931:DNA Primers; D004275:DNA, Ribosomal / Q000235:genetics; D019143:Evolution, Molecular; D020563:Gammaproteobacteria / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D016013:Likelihood Functions; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D013559:Symbiosis; D048889:Weevils / Q000382:microbiology*
chemical_list: D017931:DNA Primers; D004275:DNA, Ribosomal