Identifying Morphs of the Yellow-Legged Hornet (Vespa velutina) and Other Pests of Quarantine Importance with Geometric Morphometrics

Abstract

We assess the accuracy of geometric morphometrics (GMM) for determining the origin of insects of quarantine importance using the Asian hornet (Vespa velutina Lep.1836) as a case study. This species is highly variable, has an extensive natural distribution, and has been transported to many regions of the world. Forewing landmarks were applied to a large sample of regionally specific color morphs (previously considered “subspecies”) from across the species’ native Asian range. We reconfirm that GMM can statistically distinguish geographic variants independent of the color patterns that have heretofore been used for provenance, but which have been suspected of being unreliable. Almost all morphs in our analyses were statistically different except the centrally located V. v. variana, whose range lies between the continental V. v. auraria Smith, 1852, and V. v. nigrithorax du Buysson, 1905 morphs, and the Malaysian and Indonesian morphs. Even with moderate-sized training samples, discriminant function analysis (DFA) was able to classify geographic morphos with about 90% accuracy (ranging from 60% to 100%). We apply these results to determine the origin of a dead wasp recently intercepted in a mail parcel in Utah. Both DFA and continuous-trait maximum-likelihood clustering suggest that the Utah specimen belongs to the nigrithorax morph, which is native to southern China but now invasive in Europe, Japan, and Korea. These results are also supported by DNA barcode analysis, which groups the Utah individual with nigrithorax populations in South Korea and Japan. The relationship between variation in wing shape and genetic differentiation deserves further study, but molecular data are consistent with the GMM results suggesting that morphometric comparisons may be able to identify and provenance intercepted specimens quickly and inexpensively when molecular sequences and taxonomic specialists are unavailable.