Distribution of the endosymbiotic bacterium Cardinium in Chinese populations of the carmine spider mite Tetranychus cinnabarinus (Acari: Tetranychidae)

'Candidatus Cardinium hertigii (Cardinium)' from the Bacteroidetes group is a symbiont that has recently received attention as a reproductive manipulator of its arthropod hosts. Though the spatial distribution of symbionts depends heavily on that of their hosts, evidence has shown that dispersal limitations also have effect on some micro-organisms. In order to estimate the distribution of Cardinium in Chinese populations of the carmine spider mite, twenty seven geographical populations of Tetranychus cinnabarinus were collected and screened, using Cardinium-specific primers for the 16S ribosomal DNA. Six geographical populations collected between 30 degrees and 36 degrees N tested positive for the presence of Cardinium, whereas it could not be detected in populations collected between 19 degrees-29 degrees N and 37 degrees-46 degrees N, suggesting that the symbiont is not evenly distributed, comparing with a wider distribution of Wolbachia previously reported in the same populations. In addition, the infection rates of Cardinium seem to increase from the south to the north of China. All the six Cardinium-infected populations were found to be doubly infected with Wolbachia. Phylogenetic analysis based on the 16S rDNA gene sequence of Cardinium shows a close relationship between Cardinium in Chinese carmine spider mite and symbionts found in other species in the Tetranychidae.