Short Communication |
Corresponding author: Simon Harrison ( s.harrison@ucc.ie ) Academic editor: Michael Ohl
© 2022 Eileen Dillane, Rachel Hayden, Aidan O'Hanlon, Fidelma Butler, Simon Harrison.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Dillane E, Hayden R, O'Hanlon A, Butler F, Harrison S (2022) The first recorded occurrence of the Asian hornet (Vespa velutina) in Ireland, genetic evidence for a continued single invasion across Europe. Journal of Hymenoptera Research 93: 131-138. https://doi.org/10.3897/jhr.93.91209
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The first record of the Asian/yellow-legged hornet (Vespa velutina) in Ireland was reported in April 2021, when a single female individual was discovered in Dublin. Vespa velutina has been present in mainland Europe since 2004 and in the UK since 2016 and poses an enormous threat to European apiculture and bee-mediated pollination services. Three mitochondrial genes were sequenced from the Irish specimen to determine whether the specimen originated from the established European population or signified a new point of entry from its native range in China. Additionally, specimens from Portugal, Spain, France, Germany, and the Channel Islands were sequenced at these three genes to build on previous studies which have asserted, based solely on Cytochrome Oxidase 1 (COI) analysis, that the entire range of V. velutina in Europe represents a single invasion which has proliferated since the first record in France. Further data were retrieved from GenBank for comparison. Results reveal that the mtDNA lineage observed in Dublin is the same as that seen throughout Europe, and therefore the arrival of this species in Ireland likely represents a further spread of the ongoing European invasion.
Asian hornet, haplotype, invasive, Ireland, mtDNA
The discovery of an Asian hornet, also known as the yellow-legged hornet (Vespa velutina, Lepeletier, 1836) in Dublin in April 2021 (https://biodiversityireland.ie/asian-hornet-alert/) has raised concern among beekeepers and biologists in Ireland due to the threat posed to apiculture through predation on domestic European honey bees (Apis mellifera) and other important pollinators (
Previous studies addressing the provenance of Asian hornets in Europe have focused on the Cytochrome oxidase subunit I (COI or COX1) gene within the mitochondrial DNA (mtDNA) genome. However, the reliance on a single, relatively slow evolving/mutating gene may result in an oversimplification of invasion dynamics.
We analysed sequences at three mtDNA genes; COI, IGS2 and IGS3 in the specimen recovered from Dublin, Ireland. Due to a paucity of sequence data (other than COI) for Asian hornets in Europe, we also sought samples from continental Europe and the island of Jersey, with which to compare data from this ‘Irish’ hornet. We further sourced available sequence data from GenBank for comparison.
The V. velutina specimen was deposited with the entomological collections in the National Museum of Ireland (specimen number NMINH:2021.2.1) immediately after it’s discovery. A single middle leg was removed from the pinned specimen (Fig.
DNA extraction was carried out using DNeasy Blood and Tissue Kit (Qiagen). Three mtDNA genes were chosen for analysis; cytochrome oxidase I (COI), Intergenic spacer region 2 (IGS2) which spans COII-trnK-trnD-ATP8 and Intergenic spacer region 3 (IGS3) spanning trnR-trnN-trnE– trnS1-trnF. COI primers were from
PCRs were performed in 20 µl volumes consisting of 10 µl of 2× Plain Combi PP Master Mix (Top-Bio), 1 µM each of forward and reverse primers and 10–50 ng of DNA. PCR cycling conditions were as follows; an initial denaturation step of 3 minutes at 95 °C was followed by 40 cycles of 95 °C for 30 seconds, 48 °C for 30 seconds and 72 °C for 1 minute, with final extension step of 72 °C for 5 minutes. Electrophoresis of PCR products was performed on 1% agarose and products were excised and purified using a QIAquick Gel Extraction Kit (QIAGEN). Sequencing was performed with the forward primer for each locus using the BigDye Terminator v3.1 Cycle Sequencing Kit (Applied Biosystems). Sequencing reactions were purified using the EDTA-ethanol precipitation method described in the sequencing kit handbook and were run on an ABI3500XL DNA analyser.
Raw sequence data was examined using Chromas software 2.6.6.(Technelysium Pty Ltd) to resolve ambiguous calls. 5’ and 3’ ends of sequences were trimmed to the first shared nucleotides as gaps in sequences would be incorrectly interpreted as genetic distance during analysis rather than nucleotides that failed to be sequenced.
All sequences were used in BLAST searches which served two purposes; firstly to confirm species and secondly so that search results could be downloaded for downstream alignments and analysis.
Each locus was analysed separately. Sequences were trimmed at either end to the point where full alignments could be performed and compared with publicly available data from other studies. Alignments were performed using the Clustal Omega multiple sequence alignment tool (https://www.ebi.ac.uk/Tools/msa/clustalo/) to determine whether the Dublin specimen was of the same sequence composition as those we analysed from around Europe, and also to compare with sequence data available on GenBank from other studies
Sequencing of all three genes was successful for the V. velutina specimen discovered in Ireland. Success varied for the additional samples provided from Europe, but in all cases at least one hornet from each country was sequenced at each gene.
For CO1, 557 bp of sequence were resolved for at least one individual from each area sampled. This sequence was identical in all of the specimens we examined. The sequence from the Dublin hornet was deposited on GenBank (Accession number OP437698). Using this sequence as a BLAST query revealed that this individual was also identical to all other sequenced and deposited samples from previous studies on Asian hornets in Europe, and therefore, like those, is most closely related to V. velutina inhabiting eastern China.
In the case of IGS2, we resolved 435 bp of sequence in the Dublin specimen (GenBank accession number OP537231). This was also identical across all of the European origin specimens we sequenced. There are only two other available sequences for this gene in Europe, one from France (OU525148.1) and another from the Channel Islands (AP018461.1,
The IGS3 locus was successfully sequenced to a length of 700 bp in the Dublin specimen (GenBank accession number OP537232) and from all countries that we looked at. This sequence was identical in all hornets provided for this investigation. As with IGS2, there were just two sequences available from Europe for comparison (from the same studies). The French sample was identical to our specimens at this gene, but the Channel Islands sequence differed significantly in that there was a region of 37 bp present therein which was not seen in any of our European samples (Fig.
Summary figure of polymorphisms observed among IGS3 sequences. `…' denotes areas of homologous sequence not included for brevity (AP018461, AP018460, AP018483 from Takehashi et al 2019; OU525148 from Vespa velutina genome assembly – sample provided by Seirian Sumner in collaboration with the Sanger 25 Genomes Project and Vertebrate Genomes Project (http: //vertebrategenomesproject.org)).
Our analysis of three mtDNA loci is more comprehensive than has been previously undertaken within the range of invasive V. velutina in Europe and suggests firstly that contemporary populations of Asian hornets in Europe are of a single phylogenetic lineage, and secondly that the Irish specimen is likely to have found its way (anthropogenically) to Dublin from Europe or Britain . Our study builds on earlier work (e.g.
COI in our study specimens matched all available European sequences from other studies (
The finding that the Irish specimen and those studied from Europe are likely to represent a single invasion (founder) event is not unexpected.
Given the proximity of Ireland to Britain and continental Europe, and the existing trade links, it is prudent to expect further occasional anthropogenic introductions of V. velutina. Whether the species succeeds in establishing a self-sustaining population in Ireland is less certain. It is possible that climatic conditions in Ireland may prevent the establishment of a viable population, however the recent arrival, for example, of the Saxon wasp (Dolichovespula saxonica (Fabricius, 1793)) in the East of Ireland (
Finally, our results, along with those of other groups, suggest that the entire population of V. velutina in Europe, now potentially numbering many millions of individuals, are descended from a single mated queen arriving from China some 15–20 years ago. This demonstrates the potential for alien insects to become invasive pests via accidental imports of only very few, or single, individuals, and also the potential for biological control mechanisms, given the very low genetic diversity inherent in such populations.
This research was funded by the EU Atlantic Positive Project. The authors have declared that no competing interests exist. Specimens from Europe were generously provided by Martin Husemann (University of Hamburg, Germany), Alastair Christie (Government of Jersey); Anabela Nave (INIAV- National Institute of Agricultural and Veterinary Research, Portugal); Jose Aranha (University of Trás-os-Montes and Alto Douro, Portugal); Denis Thiery (INRAE Nouvelle-Aquitaine, France) and Ana Garcia-Perez (NEIKER - Basque Institute for Agricultural Research and Development, Spain)