Multiple long-range host shifts of major Wolbachia supergroups infecting arthropods

Abstract

AbstractWolbachiais a genus of intracellular bacterial endosymbionts found in 20–66% of all insect species and a range of other invertebrates. It is classified as a single species,Wolbachia pipientis, divided into supergroups A to U, with supergroups A and B infecting arthropods exclusively.Wolbachiais transmitted mainly via vertical transmission through female oocytes, but can also be transmitted across different taxa by host shift (HS): the direct transmission ofWolbachiacells between organisms without involving vertically transmitted gametic cells. To assess the HS contribution, we recovered 50 orthologous genes from over 1000Wolbachiagenomes, reconstructed their phylogeny and calculated gene similarity. Of 15 supergroup AWolbachialineages, 10 have similarities ranging from 95 to 99.9%, while their hosts’ similarities are around 60 to 80%. For supergroup B, four out of eight lineages, which infect diverse and distantly-related organisms such as Acari, Hemiptera and Diptera, showed similarities from 93 to 97%. These results show thatWolbachiagenomes have a much higher similarity when compared to their hosts’ genes, which is a major indicator of HS. Our comparative genomic analysis suggests that, at least for supergroups A and B, HS is more frequent than expected, occurring even between distantly-related species.