Microbiome of the wasp Vespula pensylvanica in native and invasive populations, and associations with Moku virus

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.

An experimental approach towards untangling the role of nature versus nurture in shaping the microbiome of social insects

“…The order Enterobacterales was also found to be one of the two most dominant orders in Vespa mandarinia and, to a lesser extent, in Vespa simillima 65 . Although studies detailing hornet and wasp microbiomes are still scarce, our results correspond with taxa shown to be abundant in closely related species with similar diets, such as Lactoccoccus, Gilliamella, Fructobacillus, and Leuconostoc 37, 65, 66 . Our results also confirm the contention put forward by Reeson et al 67 that V. germanica is not dependent on a specific set of symbionts.…”

“…One of the main caveats for this study was using larvae instead of eggs as the recipients for the nursing workers’ care. Had we been able to successfully carry out the experiments with eggs (which were expected to have a low bacterial load, if any 65, 66 ), we would have further minimized the effect of an already established microbiome and provided a cleaner slate to test colonization and establishment of gut symbionts. However, in our preliminary work, workers either ate the eggs or refrained from nursing them over the course of a few days, resulting in colony failure, thus leading us to use larvae.…”

Emerging Risk of Cross-Species Transmission of Honey Bee Viruses in the Presence of Invasive Vespid Species

“…The Moku virus has also been detected in honey bee and Varroa samples. Although it was detected for the first time in V. pensylvanica [ 42 , 70 , 105 ], it has also been identified in other Vespids such V. crabro in UK [ 57 ] or V. velutina in Belgium [ 61 ] and France [ 45 ]. It has also been detected in P. chinensis and P. humilis , V. germanica , and V. vulgaris [ 66 , 68 ].…”

Proposed vacuum sampling method for collecting foraging Vespula wasps at their nest entrance

“…Traditional sampling by insect netting and baited traps are both time consuming and inefficient at collecting wasps. In response, vacuum sampling methods were developed and utilised by researchers in various contexts (Leathwick et al., 1999; Pereira et al., 2016; Rothman et al., 2021; Stewart et al., 2017). Here, we describe two types of vacuum sampling methods, namely a two‐stroke petrol‐powered and a battery‐powered vacuum sampler, developed to better understand the composition of a wasp colony's diet from prey and scavenged protein items returned to their nest and the impact this predation has on the surrounding invertebrate populations.…”