title: Secondary contact and admixture between independently invading populations of the western corn rootworm, Diabrotica virgifera virgifera in Europe.
abstract: The western corn rootworm, Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae), is one of the most destructive pests of corn in North America and is currently invading Europe. The two major invasive outbreaks of rootworm in Europe have occurred, in North-West Italy and in Central and South-Eastern Europe. These two outbreaks originated from independent introductions from North America. Secondary contact probably occurred in North Italy between these two outbreaks, in 2008. We used 13 microsatellite markers to conduct a population genetics study, to demonstrate that this geographic contact resulted in a zone of admixture in the Italian region of Veneto. We show that i) genetic variation is greater in the contact zone than in the parental outbreaks; ii) several signs of admixture were detected in some Venetian samples, in a bayesian analysis of the population structure and in an approximate bayesian computation analysis of historical scenarios and, finally, iii) allelic frequency clines were observed at microsatellite loci. The contact between the invasive outbreaks in North-West Italy and Central and South-Eastern Europe resulted in a zone of admixture, with particular characteristics. The evolutionary implications of the existence of a zone of admixture in Northern Italy and their possible impact on the invasion success of the western corn rootworm are discussed.
authors.affiliation: INRA, UMR 1355 Institute Sophia Agrobiotech, Equipe Biologie des Populations Introduites, Sophia Antipolis, France. gerald.bermond@sophia.inra.fr
authors.forename: Gérald
authors.initials: G
authors.lastname: Bermond
authors.forename: Marc
authors.initials: M
authors.lastname: Ciosi
authors.forename: Eric
authors.initials: E
authors.lastname: Lombaert
authors.forename: Aurélie
authors.initials: A
authors.lastname: Blin
authors.forename: Marco
authors.initials: M
authors.lastname: Boriani
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Furlan
authors.forename: Stefan
authors.initials: S
authors.lastname: Toepfer
authors.forename: Thomas
authors.initials: T
authors.lastname: Guillemaud
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D001517:Coleoptera / Q000235:genetics*; D003433:Crosses, Genetic; D005060:Europe; D005787:Gene Frequency; D014644:Genetic Variation; D018895:Microsatellite Repeats; D011157:Population Dynamics; D062211:Spatio-Temporal Analysis