Analysing host-shift patterns of Wolbachia strains (Alphaproteobacteria) using comparative genomics

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Wolbachia is a group of Alphaproteobacteria found as intracellular endosymbionts in arthropod and nematode hosts. Based on meta-analyses, up to 52% of all terrestrial arthropod species are estimated to be infected. By far the most common strains are Wolbachia supergroup A and B and the spread among arthropod hosts has been explained by horizontal transfer. However, pathways of horizontal transfer between different hosts remain to be elucidated. Three different factors have been discussed influencing host shift patterns: (I) Phylogenetic relationships of hosts; (II) Geographic distribution of host populations; (III) Host ecology. The relative importance and contributions of these factors are discussed and comparative phylogenetic analyses based on multi-locus sequence typing (MLST) yielded incongruent results. However, we could recently show that Wolbachia MLST analyses may not be useful at all for such questions and should be replaced by genome-scale approaches.Within the proposed project we will use a phylogenomic approach to compare the relative contribution of phylogeny, ecology, and biogeography on horizontal transmission of Wolbachia strains among arthropods. For this purpose we will screen the infection status of arthropod communities of four selected plant species. Moreover, we will additionally compare Wolbachia infections of alfalfa arthropod communities between the USA (Kentucky) and Europe (Germany). After PCR screening for the presence of Wolbachia, metagenomes comprising host and Wolbachia DNA will be sequenced and assembled for selected individuals of infected arthropod species. Finally, comparative phylogenetic approaches will be used to test our three working hypotheses: (I) Infected specialists that share the same hostplant are likely to share similar Wolbachia strains; (II) Phylogenetically related infected generalists are likely to share similar Wolbachia; and (III) Arthropod communities of the same or closely related plant species harbor Wolbachia strains that differ between continents.