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My Ph.D. thesis

Diversity and impact of feminizing Wolbachia on the genetic structure of Armadillidium vulgare

Among endosymbionts, Wolbachia pipientis is the most studied reproductive parasite. This parasite also induces the most diverse effects on its hosts. By manipulating host reproduction, Wolbachia is therefore expected to affect the host genetic structuration. Armadillidium vulgare (Isopod Crustacean) is known to host two feminizing Wolbachia strains (wVulC and wVulM), as well as another unidentified feminizing genetic factor (f). This work shows the discovery of a third Wolbachia strain that is probably appeared by recombination of the two previously known strains. Wolbachia prevalence is generally low but varies greatly among populations. Genetic structuration of the host A. vulgare was analyzed both at a sub-regional scale and at a metapopulation scale. The use of microsatellite markers reveals a high genetic diversity and a low genetic structuration between populations that is compatible with isolation by distance (IBD). mtDNA shows a low polymorphism within populations and a high genetic structuration among populations, that is incompatible with IBD. As a consequence, it is proposed that feminizing factors evolve under frequency dependent selection and favor the maintenance of a low number of divergent mitotypes by genetic hitchhiking. Within the metapopulation of the RBI of Chizé, a lower female than male dispersal and a high connectivity between subpopulations seems to favor a high Wolbachia. prevalence. The analyses of sex-bias in genetic structuration indicates that feminizing factors, like Wolbachia and f can highly bias mitotype frequencies between sexes, but also induce a sex biased genetic structuration on nuclear DNA.

keywords: Armadillidium vulgareWolbachia pipientis – feminization – population genetics – metapopulation – dispersion bias

PDF of the thesis attention ! Large file !