Changes in the genetic structure of an invasive earthworm species ( Lumbricus terrestris , Lumbricidae) along an urban - rural gradient in North America.

•Bait and field individuals in the area of Calgary have a common origin.•Genetic variance within populations is high and decreases outside the urban area.•Earthworms in Canada originate from genetically diverse source populations.•Fine scale molecular markers resolve population dynamics of invasive soil species.