title: Estimation of the dispersal of a major pest of maize by cline analysis of a temporary contact zone between two invasive outbreaks.
abstract: Dispersal is a key factor in invasion and in the persistence and evolution of species. Despite the importance of estimates of dispersal distance, dispersal measurement remains a real methodological challenge. In this study, we characterized dispersal by exploiting a specific case of biological invasion, in which multiple introductions in disconnected areas lead to secondary contact between two differentiated expanding outbreaks. By applying cline theory to this ecological setting, we estimated σ, the standard deviation of the parent-offspring distance distribution, of the western corn rootworm, Diabrotica virgifera virgifera, one of the most destructive pests of maize. This species is currently invading Europe, and the two largest invasive outbreaks, in northern Italy and Central Europe, have recently formed a secondary contact zone in northern Italy. We identified vanishing clines at 12 microsatellite loci throughout the contact zone. By analysing both the rate of change of cline slope and the spatial variation of linkage disequilibrium at these markers, we obtained two σ estimates of about 20 km/generation(1/2). Simulations indicated that these estimates were robust to changes in dispersal kernels and differences in population density between the two outbreaks, despite a systematic weak bias. These estimates are consistent with the results of direct methods for measuring dispersal applied to the same species. We conclude that secondary contact resulting from multiple introductions is very useful for the inference of dispersal parameters and should be more widely used in other species.
authors.affiliation: INRA, UMR 1355, Sophia Antipolis, F-06903, France; Université de Nice Sophia Antipolis, UMR Institut Sophia Agrobiotech, Sophia Antipolis, France; CNRS, UMR 7254, Sophia Antipolis, France.
authors.forename: Gérald
authors.initials: G
authors.lastname: Bermond
authors.forename: Aurélie
authors.initials: A
authors.lastname: Blin
authors.forename: Elodie
authors.initials: E
authors.lastname: Vercken
authors.forename: Virginie
authors.initials: V
authors.lastname: Ravigné
authors.forename: Adrien
authors.initials: A
authors.lastname: Rieux
authors.forename: Sophie
authors.initials: S
authors.lastname: Mallez
authors.forename: Thibaut
authors.initials: T
authors.lastname: Morel-Journel
authors.forename: Thomas
authors.initials: T
authors.lastname: Guillemaud
mesh_terms: D063147:Animal Distribution; D000818:Animals; D001517:Coleoptera / Q000235:genetics*; D003198:Computer Simulation; D005838:Genotype; D006814:Hungary; D058865:Introduced Species; D016013:Likelihood Functions; D015810:Linkage Disequilibrium; D018895:Microsatellite Repeats; D008957:Models, Genetic; D011156:Population Density; D017524:Slovenia; D003313:Zea mays
keywords: Diabrotica virgifera; geneflow estimation; genetic clines; hybrid zone; linkage disequilibrium