Three species of Vespula have become invasive in Australia, Hawai‘i, New Zealand, and North and South America and continue to spread. These social wasp species can achieve high nest densities, and their behavioral plasticity has led to substantial impacts on recipient communities. Ecologically, they affect all trophic levels, restructuring communities and altering resource flows. Economically, their main negative effect is associated with pollination and the apicultural industry. Climate change is likely to exacerbate their impacts in many regions. Introduced Vespula spp. likely experience some degree of enemy release from predators or parasites, although they are exposed to a wide range of microbial pathogens in both their native and introduced range. Toxic baits have been significantly improved over the last decade, enabling effective landscape-level control. Although investigated extensively, no effective biological control agents have yet been found. Emerging technologies such as gene drives are under consideration.

No abstract

Social insects host a diversity of viruses. We examined New Zealand populations of the globally widely distributed invasive Argentine ant (Linepithema humile) for RNA viruses. We used metatranscriptomic analysis, which identified six potential novel viruses in the Dicistroviridae family. Of these, three contigs were confirmed by Sanger sequencing as Linepithema humile virus-1 (LHUV-1), a novel strain of Kashmir bee virus (KBV) and Black queen cell virus (BQCV), while the others were chimeric or misassembled sequences. We extended the known sequence of LHUV-1 to confirm its placement in the Dicistroviridae and categorised its relationship to closest relatives, which were all viruses infecting Hymenoptera. We examined further for known viruses by mapping our metatranscriptomic sequences to all viral genomes, and confirmed KBV, BQCV, LHUV-1 and Deformed wing virus (DWV) presence using qRT-PCR. Viral replication was confirmed for DWV, KBV and LHUV-1. Viral titers in ants were higher in the presence of honey bee hives. Argentine ants appear to host a range of' honey bee' pathogens in addition to a virus currently described only from this invasive ant. The role of these viruses in the population dynamics of the ant remain to be determined, but offer potential targets for biocontrol approaches.Social insects carry a range of viruses that can have a major effect on host population dynamics. Perhaps the best known viral community is from honey bees, which has been the focus of considerable study due to their economic importance. A range of different factors are likely to contribute to colony collapse and bee declines in general, with viruses frequently considered key players 1, 2 . A recent review noted honey bees host 24 viruses, primarily in the Dicistroviridae and Iflaviridae families 3 . Of these, the Deformed wing virus (DWV) has been suggested as a likely candidate for the majority of global honey bee colony losses during the past 50 years 4 . Such viruses, however, are not restricted to honey bees. There is increasing evidence that these 'honey bee' viruses are common in a wide range of insect hosts [5][6][7] . Other social insects have been found to carry their own unique suites of viral pathogens. For example, over the last decade four viruses have been described from the red imported fire ant (Solenopsis invicta) 8 . These were the first viruses fully described from ants. Three of these viruses are positive-sense, single-stranded RNA (ssRNA) viruses, with one (Solenopsis invicta virus-1, SINV-1) assigned taxonomically to the Dicistroviridae family, one (Solenopsis invicta virus-3, SINV-3) in a proposed new family, Solinviviridae 9 and the third currently unclassified (Solenopsis invicta virus-2, SINV-2) 8, 9 ; The fourth virus is a DNA virus, and has been placed in the family Parvoviridae 10 . One of the three ssRNA viruses, SINV-3, shows promise as a biocontrol agent as it can cause significant mortality in laboratory fire ant colonies 11 . Metatranscriptomic and pyrosequencing techniques have proven particula...

Within any one habitat, the relative fitness of organisms in a population can vary substantially. Social insects like the common wasp are among the most successful invasive animals, but show enormous variation in nest size and other fitness‐related traits. Some of this variation may be caused by pathogens such as viruses that can have serious consequences in social insects, which range from reduced productivity to colony death. Both individual immune responses and colony‐level traits such as genetic diversity are likely to influence effects of pathogen infections on colony fitness. Here we investigate how infections with Kashmir Bee Virus (KBV), immune response and intracolony genetic diversity (due to queen polyandry) affect nest size in the invasive common wasp Vespula vulgaris. We show that KBV is highly prevalent in wasps and expression of antiviral immune genes is significantly increased with higher viral loads across individuals. Patriline membership within a nest did not influence KBV susceptibility or immune response. A permutational MANCOVA revealed that polyandry, viral load and expression of the immune gene Dicer were significant predictors of variation in nest size. High intracolony genetic diversity due to polyandry has previously been hypothesized to improve colony‐level resistance to parasites and pathogens. Consistent with this hypothesis, we observed genetically diverse colonies to be significantly larger and to produce more queens, although this effect was not driven by the pathogen we investigated. Invasive wasps clearly suffer from pathogens and expend resources, as indicated here by elevated immune gene expression, toward reducing pathogen‐impact on colony fitness.

No abstract