Rapid spread of a bacterial symbiont in the sweetpotato whitefly, Bemisia tabaci

Inherited intracellular bacterial symbionts are strong agents of evolutionary change in host populations. Rickettsia, a lineage of bacteria in the Alphaproteobacteria, has been known primarily as an arthropod-vectored pathogen of humans. More recently these bacteria have been found to be common vertically transmitted secondary (facultative) symbionts of arthropods and other invertebrates. Here we report the rapid spread of a Rickettsia in the Rickettsia bellii clade in the whitefly Bemisia tabaci (Biotype B) in the Southwestern United States. Alcohol preserved samples of whiteflies from several sites in Arizona, New Mexico and California collected in 2000, 2003 and 2006 were used to determine the frequency of the infection at these three time-points. Across all sites, the frequency of infection rose from 3% in 2000 to 51% in 2003, to 97% in 2006. The rapid spread of the infection suggests one of three possibilities under investigation: horizontal transfer of the bacterium, strong fitness benefits, or reproductive manipulation.