Abstract
Wolbachia are maternally inherited endosymbiotic bacteria of arthropods and nematodes. In arthropods, they manipulate the reproduction of their hosts to facilitate their own spread in host populations, causing cytoplasmic incompatibility, parthenogenesis induction, feminization of genetic males and male-killing. In this study, we investigated Wolbachia infection and studied wsp (Wolbachia surface protein) sequences in three wasp species associated with the unisexual galls of A. mukaigawae with the aim of determining the transmission mode and the reason for multiple infections of Wolbachia. Frequency of Wolbachia infected populations for A. mukaigawae, Synergus japonicus (inquiline), and Torymus sp. (parasitoid) was 75%, 100%, and 100%, respectively. Multiple Wolbachia infections were detected in A. mukaigawae and S. japonicus, with 5 and 8 Wolbachia strains, respectively. The two host species shared 5 Wolbachia strains and were infected by identical strains in several locations, indicating horizontal transmission of Wolbachia. The transmission potentially takes place through gall tissues, which the larvae of both wasps feed on. Furthermore, three recombination events of Wolbachia were observed: the strains W8, W2 and W6 apparently have derived from W3 and W5a, W6 and W7, W4 and W9, respectively. W8 and W2 and their respective parental strains were detected in S. japonicus. W6 was detected with only one parent (W4) in S. japonicus; W9 was detected in Torymus sp., suggesting horizontal transmission between hosts and parasitoids. In conclusion, our research supports earlier studies that horizontal transmission of Wolbachia, a symbiont of the Rickettsiales order, may be plant-mediated or take place between hosts and parasitoids. Our research provides novel molecular evidence for multiple recombination events of Wolbachia in gall wasp communities. We suggest that genomic recombination and potential plant-mediated horizontal transmission may be attributable to the high levels of multiple Wolbachia infections observed in A. mukaigawae and S. japonicus.
Highlights
Wolbachia are maternally inherited endosymbiotic bacteria of the family of Anaplasmataceae and infect filarial nematodes and arthropods, including insects, mites, spiders and isopods [1,2]
Wolbachia Infection in A. mukaigawae Communities A total of 570 unisexual galls of A. mukaigawae were collected from eight locations during September–December 2010 and 2011
The high levels of multiple infections comparable to what we found in the A. mukaigawae associated communities are infrequent among insects in general, it is relatively common for host insects to be infected with two or three Wolbachia strains [5,52]
Summary
Wolbachia are maternally inherited endosymbiotic bacteria of the family of Anaplasmataceae and infect filarial nematodes and arthropods, including insects, mites, spiders and isopods [1,2]. In arthropods, these intracellular bacteria can manipulate host reproduction to enhance their own spread throughout host populations, causing cytoplasmic incompatibility, parthenogenesis induction, feminization of genetic males and male-killing [3]. One particular reported frequent observation of Wolbachia being naturally transmitted horizontally from infected to uninfected wasp larvae sharing a common butterfly egg [18]
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