Evolutionary biology of Wolbachia, selfish bacterial symbionts in insects : natural history of cytoplasmic incompatibility in a planthopper and sex ratio distortion in moths.

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Laodelphax striatellus individuals were sampled during 1997-1999 from Honshu in order to examine the spatio-temporal dynamics in the prevalences of Wolbachia infection. PCR assay with ftsZ gene indicated that L. striatellus populations were infected with the B clade of Wolbachia only. Based on the analysis of allozyme polymorphism, it was inferred that the level of long distance migration in L. striatellus is not as high as to prevent genetic differentiation among geographical populations. The long distance migration was discussed in relation to the advance of Wolbachia infection wave in L. striatellus. The relationships between spread of Wolbachia infection and each of mitochondrial DNA variation and reproductive isolation in host insects were discussed under the zoogeographical context.Multiple, maternal lineages expressing thelygeny trait were obtained from each of Ostrinia furnacalis and O. scapulalis populations. Wolbachia infection and feminization of genetic males were strongly associated, and therefore Wolbachia infection was considered to cause feminization in both Ostrinia species. The phylogenetic position of the Wolbachia infected with Ostrinia among major strains of Wolbachia was estimated using DNA sequences of the ftsZ gene. Wolbachia infection showed low prevalences in each of the two Ostrinia species, and high rates of vertical transmission in the laboratory. Five maternal lineages of O. scapulalis showed thelygeny although they were not associated with Wolbachia infection (uSR lineages). Antibiotic treatements and PCR assays indicated that thelygeny in each of the five uSR lineages was not bacterially induced, although was induced by a cytoplasmic/W chromosomal factor(s). The thelygeny in each of the uSR lineages was considered to be underlied with some mechanism(s) other than any of those already known from Lepidoptera.