Abstract
Invasive species present a worldwide concern as competition and pathogen reservoirs for native species. Specifically, the invasive social wasp, Vespula pensylvanica, is native to western North America and has become naturalized in Hawaii, where it exerts pressures on native arthropod communities as a competitor and predator. As invasive species may alter the microbial and disease ecology of their introduced ranges, there is a need to understand the microbiomes and virology of social wasps. We used 16S rRNA gene sequencing to characterize the microbiome of V. pensylvanica samples pooled by colony across two geographically distinct ranges and found that wasps generally associate with taxa within the bacterial genera Fructobacillus, Fructilactobacillus, Lactococcus, Leuconostoc, and Zymobacter, and likely associate with environmentally-acquired bacteria. Furthermore, V. pensylvanica harbors—and in some cases were dominated by—many endosymbionts including Wolbachia, Sodalis, Arsenophonus, and Rickettsia, and were found to contain bee-associated taxa, likely due to scavenging on or predation upon honey bees. Next, we used reverse-transcriptase quantitative PCR to assay colony-level infection intensity for Moku virus (family: Iflaviridae), a recently-described disease that is known to infect multiple Hymenopteran species. While Moku virus was prevalent and in high titer, it did not associate with microbial diversity, indicating that the microbiome may not directly interact with Moku virus in V. pensylvanica in meaningful ways. Collectively, our results suggest that the invasive social wasp V. pensylvanica associates with a simple microbiome, may be infected with putative endosymbionts, likely acquires bacterial taxa from the environment and diet, and is often infected with Moku virus. Our results suggest that V. pensylvanica, like other invasive social insects, has the potential to act as a reservoir for bacteria pathogenic to other pollinators, though this requires experimental demonstration.
Highlights
Social insects present some of the most widespread and damaging examples of invasive species worldwide [1]
We investigated three lines of inquiry to better understand the microbial communities of our study organism: First, does V. pensylvanica associate with a defined microbiome, is there any evidence of environmental transmission of microbes, and are their microbiomes similar in the native and invasive range? Second, does this wasp species associate with endosymbiotic bacteria? Third, are there associations between Moku virus and the wasp microbiome?
After removing likely reagent contamination identified in our control blanks, the top 10 most abundant bacterial families and their relative abundances in our samples were as follows: Leuconostocaceae (32.8%), Enterobacteriaceae (17.1%), Microbacteriaceae (9.9%), Streptococcaceae (3.6%), Lactobacillaceae (3.6%), Halomonadacae (3.1%), Rhizobiaceae (2.9%), Acetobacteraceae (2.6%), Rickettsiaceae (2.4%), and Moraxellaceae (1.9%), while all other families combined comprised an average of 20.2% of the proportional abundance of taxa (Fig 2)
Summary
Social insects present some of the most widespread and damaging examples of invasive species worldwide [1]. During the 20th century, members of the genus Vespula have become invasive in South America, New Zealand, Australia, South Africa, and a variety of islands where native arthropods have not coevolved with predatory vespines [6] Given that these species are generalist predators, opportunistic scavengers, and often reach extreme densities in new environments, the effects on native arthropod communities have been profound. Occasionally in the native range [10] and more commonly in subtropical Hawaii [7, 11], colonies survive the winter and attain tremendous sizes through a second or third season of growth [7] These perennial colonies have an outsized effect on arthropod communities, collecting much more prey than typical annual colonies, and exerting predation pressure throughout the year [11]. Understanding the ecological, genetic and social factors that have facilitated the successful Hawaiian invasion and the rise of the large and long-lived colony phenotype in Hawaii will be essential in mitigating the effects of the invasion and avoiding similar invasions elsewhere
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