Data from: Diversity and distribution of Wolbachia in relation to geography, host plant affiliation and life cycle of a heterogonic gall wasp

Background: The maternally inherited endosymbiont Wolbachia is widespread
in arthropods and nematodes and can play an important role in the ecology
and evolution of its host through reproductive manipulation. Here, we
survey Wolbachia in Belonocnema treatae, a widely distributed North
American cynipid gall forming wasp that exhibits regional host
specialization on three species of oaks and alternation of sexually and
aseuxlly reproducing generations. We investigated whether patterns of
Wolbachia infection and diversity in B. treatae are associated with the
insect's geographic distribution, host plant association, life cycle,
and mitochondrial evolutionary history. Results: Screening of 463
individuals from 23 populations including sexual and asexual generations
from all three host plants across the southern U.S. showed an average
infection rate of 56% with three common Wolbachia strains: wTre1-3 and an
additional rare variant wTre4. Phylogenetic analysis based on wsp showed
that these strains are unrelated and likely independently inherited. We
found no difference in Wolbachia infection frequency among host plant
associated populations or between the asexual and sexual generations, or
between males and females of the sexual generation. Partially incomplete
Wolbachia transmission rates might explain the occurrence of uninfected
individuals. A parallel analysis of the mitochondrial cytochrome oxidase I
gene in B. treatae showed high mtDNA haplotype diversity in both infected
and uninfected populations suggesting an ancestral infection by Wolbachia
as well as a clear split between eastern and western B. treatae mtDNA
clades with a sequence divergence of > 6%. The strain wTre1 was
present almost exclusively in the western clade while wTre2 and wTre3
occur almost exclusively in eastern populations. In contrast, the same
strains co-occur as double-infection in Georgia and triple-infections in
two populations in central Florida. Conclusions: The diversity of
Wolbachia across geographically and genetically distinct populations of B.
treatae and the co-occurrence of the same strains within three populations
highlights the complex infection dynamics in this system. Moreover, the
association of distinct Wolbachia strains with mitochondrial haplotypes of
its host in populations infected by different Wolbachia strains suggests a
potential role of the endosymbiont in reproductive isolation in B.
treatae.