Our genetic analyses suggest two independent colonization events: one into northeastern Germany and one into the Baltic States. Our genetic and morphological analyses suggest similarity between Russian and both expanding populations. An important source of expanding populations might be located in eastern European steppe. The climate in this region is distinguished by cold winters and thus more comparable to that in the newly invaded C. punctorium habitats. The invading populations could therefore be preadapted to the novel conditions, which might facilitate their initial establishment.