Concordant evolution of a symbiont with its host insect species: Molecularphylogeny of genus Glossina and its bacteriome-associated endosymbiont, Wigglesworthia glossinidia

Many arthropods with restricted diets rely on symbiotic associations for fu ll nutrition and fecundity. Tsetse flies (Diptera: Glossinidae) harbor thre e symbiotic organisms in addition to the parasitic African trypanosomes the y transmit. Two of these microorganisms reside in different gut cells, whil e the third organism is harbored in reproductive tissues and belongs to the genus Wolbachia. The primary symbiont (genus Wigglesworthia glossinidia) l ives in differentiated epithelial cells (bacteriocytes) which form an organ (bacteriome) in the anterior gut, while the secondary (S) symbionts are pr esent in midgut cells. Here we have characterized the phylogeny of Wigglesw orthia based on their 16S rDNA sequence analysis from eight species represe nting the three subgenera of Glossina: Austenina (=fusca group), Nemorhina (=palpalis group), and Glossina (=morsitans group). Independently, the ribo somal DNA internal transcribed spacer-2 (ITS-2) regions from these species were analyzed. The analysis of Wigglesworthia indicated that they form a di stinct lineage in the gamma subdivision of Proteobacteria and display conco rdance with their host insect species. The trees generated by parsimony con firmed the monophyletic taxonomic placement of Glossina, where fusca group species formed the deepest branch followed by morsitans and palpalis groups , respectively. The placement of the species Glossina austeni by both the t raditional morphological and biochemical criteria has been controversial, R esults presented here, based on both the ITS-2 and the symbiont 16S rDNA se quence analysis, suggest that Glossina austeni should be placed into a sepa rate fourth subgenus, Machadomyia, which forms a sister-group relationship with the morsitans group species.