Estimation of the dispersal of a major pest of maize by cline analysis of a temporary contact zone between two invasive outbreaks

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 analyzing both the rate of change of cline slop...