Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Chemical and genetic evidences that multiple hornet colonies attack honeybee colonies.

Abstract

The yellow-legged hornet, Vespa velutina nigrithorax, is an invasive species that is causing numerous ecological and economic problems, particularly for beekeepers, whose apiaries are seriously affected by hornet predation. The effects may be intensified if hornet workers from different colonies are preying upon bees from the same apiary. Therefore, to determine whether such could occur, we sampled hornets found within identifiable colonies versus in front of beehives. We employed two complementary methodological approaches: the analysis of chemical markers (i.e., cuticular hydrocarbons) and genetic markers (i.e., microsatellites). Although there was chemical variation among hornets, we determined that at least two chemically homogeneous hornet groups could be found within each apiary studied (using K-means clustering). Furthermore, when hornet chemical dissimilarity was quantified at three different levels (within apiaries, within hornet colonies, and between hornet colonies), we discovered that the within-apiary dissimilarity was intermediate relative to within-colony and between-colony dissimilarity, suggesting that the hornets within a given apiary represented a mixture of individuals from more than one colony. Based on the genetic markers, hornet genetic diversity was low at the population level, as expected for this introduced species. That said, the genetic results mirrored the chemical results: genetic dissimilarity was larger between colonies and smaller within colonies. However, the hornets within a given apiary displayed an intermediate dissimilarity value. Consequently, both our chemical and genetic findings suggested that apiaries could be attacked by hornets from more than one colony.