Broad ecological threats of an invasive hornet revealed through a deep sequencing approach.

Abstract

Most terrestrial invertebrates are in considerable decline, and the range expansion of the invasive hornet, Vespa velutina nigrithorax, poses an additional threat. Although now found in much of western Europe, the full extent of the hornet's predatory activity remains unexplored. While impacts on honey bees are well-documented, evidence of a wider dietary spectrum is emerging, indicating potentially broad ecological ramifications. Here, we conduct the first large-scale study of the diet of V. velutina, utilising deep sequencing to characterise the larval gut contents of over 1500 samples from Jersey, France, Spain, and the UK. Our results indicate that V. velutina is a highly flexible predator, enabling its continued range expansion capacity. Analyses detected 1449 taxa, with greater prey richness in samples from southern latitudes, and considerable spatiotemporal variation in dietary composition. Hymenoptera, Diptera, Hemiptera, Coleoptera, Lepidoptera, and Araneae were the most frequently occurring orders predated, each characterised by high taxonomic diversity. The honey bee Apis mellifera was the most abundant species, being found in all sampled nests and showing greater relative read numbers with increasing apiary density and proximity, supporting concerns for the impact of V. velutina on apiculture. Notably, 43 of the 50 most commonly predated invertebrates were also flower visitors, including 4 common bumblebee species, indicating potentially substantial risks to wild pollinators. These data provide wide and deep evidence to support risk evaluation of this species and its potential environmental impact as it spreads across Europe.