Novel host-bacterial symbioses revealed: characterization of Wolbachia in arthropods of western North America

Arthropod-bacterial symbioses are prevalent and play significant roles in ecosystems and the economy, and in some cases, habitat invasion. Wolbachia bacteria form symbiotic associations with a wide range of arthropod hosts and can affect both host reproduction and resistance to viral infections. The extent to which Wolbachia infects different arthropod species is fundamental not only to host biology, but also to the health of humans, ecosystems, and agriculture. Much of what we know about the effects of Wolbachia comes from a few key taxa, such as the model organism Drosophila melanogaster and the mosquito vector of human disease, Aedes aegypti. The majority of arthropods, even at higher taxonomic levels, have not been tested for infection, with a lack of surveys conducted in western North America. We screened and characterized Wolbachia diversity in arthropods in 2 types of collections in western North America: broad surveys and targeted collections of species known to be infected with Wolbachia Our goals were to (1) find new Wolbachia strains and hosts, (2) characterize Wolbachia in commonly studied taxa to see whether there are different infection frequencies or strain types in this location, and (3) compare new Wolbachia strains in western North America to previously characterized strains. PCR screening of broadly sampled arthropods with Wolbachia-specific 16S rDNA (W16S) identified 5 novel host species. Three of these are invasive: a ground beetle, Nebria brevicollis (Coleoptera: Carabidae); a cereal crop agricultural pest, Oulema melanopus (Coleoptera: Chrysomelidae); and a residential nuisance pest, Raglius alboacuminatus (Hemiptera: Rhyparochromidae). The crab spider Philodromus dispar (Araneae: Philodromidae) is nonnative, though not considered invasive, and the hyaline grass bug Liorhyssus hyalinus (iiemiptera: Rhopalidae) is of undetermined origin. To characterize 9 novel Wolbachia strains in our collections, we analyzed the 5-gene MultiLocus Sequence Type (MLST) and the Wolbachia surface protein gene (wsp). We identified 10 novel alleles among 5 MLST genes and 10 novel alleles of the highly variable regions (HVR) of wsp. This is the first report of Wolbachia hosts and strain identification from the Pacific Northwest and Rocky Mountain regions. These studies contribute to our understanding of the natural history of arthropod hosts, the biogeography of Wolbachia, and host-symbiont evolution. Moreover, strain identification is the first step in implementing Wolbachia-based biocontrol for conservation and pest mitigation, including control of the invasive N. brevicollis, O. melanopus, and R. alboacuminatus reported herein.