Stratified dispersal and increasing genetic variation during the invasion of Central Europe by the western corn rootworm,Diabrotica virgifera virgifera

Abstract

Invasive species provide opportunities for investigating evolutionary aspects of colonization processes, including initial foundations of populations and geographic expansion. Using microsatellite markers and historical information, we characterized the genetic patterns of the invasion of the western corn rootworm (WCR), a pest of corn crops, in its largest area of expansion in Europe: Central and South-Eastern (CSE) Europe. We found that the invaded area probably corresponds to a single expanding population resulting from a single introduction of WCR and that gene flow is geographically limited within the population. In contrast to what is expected in classical colonization processes, an increase in genetic variation was observed from the center to the edge of the outbreak. Control measures against WCR at the center of the outbreak may have decreased effective population size in this area which could explain this observed pattern of genetic variation. We also found that small remote outbreaks in southern Germany and north-eastern Italy most likely originated from long-distance dispersal events from CSE Europe. We conclude that the large European outbreak is expanding by stratified dispersal, involving both continuous diffusion and discontinuous long-distance dispersal. This latter mode of dispersal may accelerate the expansion of WCR in Europe in the future.

Contrasted invasion processes imprint the genetic structure of an invasive scale insect across southern Europe

“…We thus can confidently conclude that once introduced accidentally from South-Western France, the scale expanded its range through natural, gradual, short-distance dispersal along more or less continuous host forests, and finally reached the fragmented edge of the host distribution either through a steppingstone colonization from South-Eastern France, or through a local expansion from the closest populations in Liguria. Such stratified dispersal is usually observed for insects expanding into a fragmented habitat, for example, colonizing a patchy host (Ciosi et al, 2011;Gilioli et al, 2013). Fully analysing and understanding the local expansion patterns would require the development of genetic and modelling approaches at regional and landscape scales (Etherington, 2011) to take into account habitat characteristics and connectivity.…”

“…Invasive species may colonize distant patches and new environments by long-distance dispersal and/or expand into adjacent habitats by regional diffusion. Complex dispersal patterns combining short-distance diffusion with long-distance dispersal are referred to as stratified dispersal, which can lead to greater rates of expansion than that observed in cases of species without long-distance dispersal (Shigesada et al, 1995;Ciosi et al, 2011). Short-and longrange dispersal may be facilitated by biotic (Liebhold and Tobin, 2008) or abiotic dispersal vectors (for example, wind: Ahmed et al, 2009;Reynolds and Reynolds, 2009).…”

Évaluation socioéconomique des politiques phytosanitaires. Le cas de la chrysomèle du maïs

“…Dans leur revue de la littérature sur la dynamique des populations de chrysomèle, Meinke et al (2009) (Ciosi et al, 2011 ;Gray et al, 2009). Pour autant, l'évaluateur doit arbitrer entre le réalisme du modèle et la disponibilité des données.…”

Exotic Insects in Italy: An Overview on Their Environmental Impact

“…In fragmented habitats very specialized species or those species with poor dispersal ability may suffer more than generalistic and invasive species. The Italian outbreaks of Cameraria ohridella, Diabrotica virgifera virgifera, and Lissorhoptrus oryzophilus have expanded by stratified dispersal, involving both continuous diffusion and discontinuous long-distance dispersal (Ciosi et al, 2011;Gilbert et al, 2004;Lupi et al, 2010).…”