Species invasions provide numerous unplanned and frequently, but imperfectly, replicated
experiments that can be used to better understand the natural world. Classic studies by
Darwin, Grinnell, Elton and others on these species-invasion experiments provided
invaluable insights for ecology and evolutionary biology. Recent studies of invasions have
resulted in additional insights, six of which we discuss here; these insights highlight the
utility of using exotic species as 'model organisms'. We also discuss a nascent hypothesis …