Invasive species often cause serious economic problems, but they can also serve as a useful test-bed for theories of natural, slower range expansions. Based on analyses of genetic variation, Senckenberg researchers and an Australian colleague have investigated the origin, routes of colonization, and rate of spread of the invasive slug Deroceras invadens. Their results can be compared against historical records of when this species first turned up around the world. The study was recently published in the Journal of Molluscan Studies.