Luca Carisio, Jacopo Cerri , Simone Lioy, Ettore Bianchi, Sandro Bertolino, Marco Porporato

Alien species invasion could lead to the replacement of native species with similar ecological requirements. Vespa velutina is an invasive hornet recently established in Europe, that is raising concern due to the associated economic and ecological impacts toward managed and wild pollinators besides to the potential competition and replacement of native wasp species. This led to the inclusion of V. velutina in the European list of Invasive Alien Species of Union concern. Nevertheless, V. velutina impacts on the native wasp community is poorly understood. We analysed the influence of V. velutina abundance on the European hornet Vespa crabro in a four-year invaded area in Italy. Moreover, we assessed the impacts of its presence on V. crabro, Vespula vulgaris and Vespula germanica, by comparing the invaded area with an uninvaded one. A Bayesian Generalized Linear Model, implemented to control some relevant environmental confounders, indicate that the relationship between Vespa species was positive at low abundances, while for high values of V. velutina the two species did not covary anymore. The distribution of V. crabro, V. vulgaris and V. germanica showed a considerable overlap between the invaded and uninvaded areas. Overall, the results bring to the conclusion that native Vespidae have probably avoided or minimised a competition pressure, and therefore the presence of V. velutina has not led to an evident replacement of V. crabro and Vespula species. This provides reassurance regarding the conservation status of native European Vespidae following V. velutina invasion.