International Journal of Pest Management ISSN: 0967-0874 (Print) 1366-5863 (Online) Journal homepage: http://www.tandfonline.com/loi/ttpm20 Spread modelling: a suitable tool to explore the role of human-mediated dispersal in the range expansion of the yellow-legged hornet in Europe Christelle Robinet, Eric Darrouzet & Christelle Suppo To cite this article: Christelle Robinet, Eric Darrouzet & Christelle Suppo (2018): Spread modelling: a suitable tool to explore the role of human-mediated dispersal in the range expansion of the yellow-legged hornet in Europe, International Journal of Pest Management, DOI: 10.1080/09670874.2018.1484529 To link to this article: https://doi.org/10.1080/09670874.2018.1484529 Published online: 30 Jul 2018. Submit your article to this journal View Crossmark data Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ttpm20 INTERNATIONAL JOURNAL OF PEST MANAGEMENT https://doi.org/10.1080/09670874.2018.1484529 Spread modelling: a suitable tool to explore the role of human-mediated dispersal in the range expansion of the yellow-legged hornet in Europe Christelle Robineta , Eric Darrouzetb and Christelle Suppob aINRA, UR633 Zoologie Forestiere, Orleans, France; bInstitut de Recherche sur la Biologie de l’Insecte, UMR 7261, CNRS – Universite de Tours, Tours, France ABSTRACT ARTICLE HISTORY Invasive species can spread locally on their own and can be introduced at long distance by Received 15 March 2018 humans. Here, we show how a spread model can be used to explore the role of humans in Accepted 29 May 2018 the range expansion of the invasive yellow-legged hornet, Vespa velutina nigrithorax,in KEYWORDS Europe with a special focus on some islands. In 2017, the hornet distribution in France, southern Belgium, south-eastern Germany and northern Spain could largely be explained by Biological invasion; ’ dispersal; introduction; the insect s own dispersal while the occurrence in Portugal, Italy, the Netherlands and Great island; pest management; Britain likely results from human-mediated dispersal. However, in the following years, it Vespa velutina could spread to Portugal, Italy and Great Britain also by its own means. The yellow-legged hornet has likely reached the Channel Islands by its own flight but it could hardly reach the Mediterranean islands. Hence, the infestation in Majorca likely results from an accidental introduction. When simulating human-mediated dispersal in the Mediterranean islands, the hornet density would remain relatively low anyhow. Assessing the means of dispersal is important in terms of pest management as the target is either to reduce the spread rate and the population density, or to reduce the risk of entry. 1. Introduction Several pathways explaining the invasion of alien species have been highlighted (Hulme 2009), such as There are more and more biological invasions docu- live plant imports for the introduction of plant pests mented throughout the world and they are mainly driven by international trade (Pysek et al. 2010) (Liebhold et al. 2012) or transportation of wood and/or climate warming (Walther et al. 2009). The products for the introduction of forest pests number of biological invasions is unlikely to drop (Yemshanov et al. 2012). Although accidental trans- since there is no sign of alien species saturation so portation of species are generally associated with a far (Seebens et al. 2017). Alien species have large closely linked commodity, they can also be trans- economic impacts (Bradshaw et al. 2016) and ported with another commodity neither providing a increasing pressures on biodiversity (Butchart et al. habitat nor a resource to the species. In this case, 2010). Furthermore, in Europe, the spread rate of the alien species is simply a hitchhiker. Identifying alien insect species is significantly higher for species the introduction pathway is thus a very detected after 1990 than before, thus showing the complex task. potential effects of political changes on the freedom If human-mediated dispersal can explain the dis- of trade (e.g., the collapse of the Iron Curtain and persal of a species from one continent to another, it European Union facilitating the trade within can also explain long distance jumps observed European countries) (Roques et al. 2016). The rapid within the invaded range. For instance, the horse- spread of several plant pests has been observed dur- chestnut leaf miner, Cameraria ohridella, is known ing the last few years. For instance, the western to disperse over long distance in Europe with the conifer-seed bug, Leptoglossus occidentalis, was first transport of infested leaves by car traffic (Gilbert detected in Europe (Italy) in 1999 and it is now pre- et al. 2004). The pine wood nematode, sent in 26 European countries (CABI 2017a). The Bursaphelenchus xylophilus, is known to disperse at box tree moth, Cydalima perspectalis, was detected long distance in China with the transport of infested in Europe (Germany) in 2007 and it is now present wood material (Robinet et al. 2009). The emerald in 20 European countries (CABI 2017b). These ash borer, Agrilus planipennis, is known to disperse rapid spreads question the role of humans in the at long distance in the US with the transport of fire dispersal of pests at long distance. wood (Muirhead et al. 2006). CONTACT Christelle Robinet [email protected] ß 2018 Informa UK Limited, trading as Taylor & Francis Group 2 C. ROBINET ET AL. Identifying the pest pathway and disentangling spreading in Spain, Portugal, Italy, Germany, the role of human mediated dispersal from active Belgium and Great Britain (Figure 1). A young dispersal is challenging at both large and fine spatial queen was also recently detected in Switzerland scales. Several tools are available with large variation (JRC 2017). The occurrence of satellite colonies far in their effectiveness. For instance, interception data from the species main distribution in France are largely biased and cannot be used to assess the observed in 2009 may suggest human-mediated dis- invasion likelihood with the transportation of a persal within France (Darrouzet 2010). However, a given commodity because inspection usually targets study based on spread simulations concluded that a set of quarantine pests and commodities only these satellite colonies do not necessarily result from (Eschen et al. 2015). Sentinel trees can be used to accidental transport by human activities (Robinet estimate the likelihood of transporting a pest with a et al. 2017). The estimated spread rate of the living plant grown in a given area (Roques et al. yellow-legged hornet in France was 78 km/year and 2015). Genetic analyses can be done to track the ori- this high spread rate is consistent with data gin of the individuals among continents (Boissin collected in flight mill experiments (Sauvard et al. et al. 2012; Lombaert et al. 2010) but also at finer 2018). Since the hornet invasion in Europe likely scales (Robinet et al. 2012). However when species results from the introduction of very few or a single can disperse very fast on their own and when there multi-mated female with the import of bonsai pots is low genetic variability, the populations are (Arca et al. 2015), French colonies can produce generally not differentiated and thus genetic analyses early diploid males as a result of inbreeding are poorly informative. (Darrouzet et al. 2015) linked to a genetic bottleneck The yellow-legged hornet, Vespa velutina (Arca et al. 2015). Consequently, the genetic vari- nigrithorax, is one of these fast spreading invaders. ability would probably be too low in Europe to use Native to Asia, it was first discovered in Europe genetic markers in order to disentangle human- (France) in 2005 (Haxaire et al. 2006; Monceau mediated dispersal from active dispersal within this et al. 2014). Niche models predict that a large part area. We thus use the spread model previously of Europe is suitable for the species establishment developed for France to test various hypotheses and this suitable area could further expand with cli- regarding the means of dispersal to different places mate warming (Barbet-Massin et al. 2013, 2018; in Europe. Villemant et al. 2011a). The yellow-legged hornet is In this study, we determine the potential spread now present in a large part of France and it is also of the yellow-legged hornet with and without Figure 1. Observed spread (in red) of the yellow-legged hornet in Europe (in September 2017; derived from the map pro- vided by Q. Rome, MNHN-INPN, http://frelonasiatique.mnhn.fr) and the islands considered in this study. The Channel Islands (Jersey and Guernsey) and Majorca were colonized by the hornet whereas Corsica, Sardinia and Sicilia were not colonized. The black dot in France indicates the location of first record of the yellow-legged hornet in Europe. Source: reproduced by the authors from the map provided by Q. Rome, MNHN-INPN, http://frelonasiatique.mnhn.fr INTERNATIONAL JOURNAL OF PEST MANAGEMENT 3 human-mediated dispersal at the European scale 3.1. Reaction-diffusion model and at local scales. Since several islands have been The reaction-diffusion model is based on the Fisher colonized (Great Britain, Majorca and the Channels equation: Islands; Figure 1), spread modelling was used to ! determine whether the invasion of yellow-legged @N @2N @2N N ¼ D þ þ rN 1À (1) hornet on these islands is likely due to human activ- @t @x2 @y2 K ity or due to the hornet own dispersal. On the other À2 hand, several islands seem still free from the hornet where N is nest density (km ) which depends on time t and spatial location (x,y), D is the diffusion (e.g., Corsica, Sardinia, and Sicilia), and we explored À coefficient (D ¼ 984 km2 year 1), K is carrying cap- whether they could be colonized either by natural À À acity (0.06 nest.km 2), and r is growth rate (year 1) spread or by human activities.