Several evolutionary phenomena in arthropods were shown to be due to the presence of inherited symbionts, e.g., sex-ratio-distortion, cytoplasmic incompatibility, conferring resistance to pathogens, nutritional mutualism and others. All these phenomena may be induced by Wolbachia, an alpha-proteobacterium that is estimated to occur in about 60% of all terrestrial arthropods. Other endosymbionts are comparatively understudied and known only from a few model systems. Wolbachia is exclusively inherited maternally via the germ line, but horizontal transfer across host species boundaries seems to be a common theme. Using a PCR-based Multi Locus Sequence Typing (MLST) we investigated possible routes for horizontal transfer in bees and provide a framework by which precise assumptions about shared evolutionary histories of Wolbachia and a host taxon can be modeled and tested. Wolbachia diversity is classified into different supergroups. In general, Wolbachia are either widespread, opportunistic reproductive parasites of arthropods (supergroups A and B) or essential mutualists in a single group of filarial nematodes, including many species of medical significance (supergroup C and D). Other distinct Wolbachia strain groups are known only from a small number of hosts: supergroup E is found in springtails, supergroup H in termites. Using complete genomes we were able to present a first comprehensive phylogenomic analysis of Wolbachia supergroup relationships. Our results suggest that the ability of some arthropod-infecting Wolbachia to universally infect and to adapt to a broad range of hosts quickly is restricted to a single monophyletic lineage (containing supergroups A and B). Thus, the currently observable pandemic has likely a single evolutionary origin and is unique within the radiation of Wolbachia strains. 

Seminario organizado por el Departamento de Biodiversidad y Biología Evolutiva del Museo Nacional de Ciencias Naturales (MNCN), CSIC, y retransmitido en directo a través de Cienciatk por el Servicio de Audiovisuales-Mediateca, MNCN-CSIC.