What, then, is the ecological difference between humans as a dispersal agent, and, say, seabirds as a dispersal agent? When we study Hawaiian native plants, are we not studying "how natural selection influenced organisms after their introduction, or as a consequence of the introduction of other species"? The system is still one of an organism having been brought to some isolated location to which it could not otherwise have gotten on its own. The whole study of island biodiversity is inherently the study of introductions of "alien" species by various means, except in the case of continental islands formerly connected to the mainland. Jason Hernandez East Carolina University
--- On Tue, 5/11/10, ECOLOG-L automatic digest system <lists...@listserv.umd.edu> wrote: But that question is easy to answer. If humans put the species in a place or it arrived in a place that it would not have gotten to on its own, then it is introduced, otherwise it is native or natural. Clearly this is a mere consequence of the short history of humans as dispersal agents on the planet, but it is a good enough definition for 99% of the cases - just check the classic by Elton. We already have the term "naturalized" which basically means it's here to stay and there is nothing we can do about it. I personally think that for almost all intents and purposes, those definitions work. When they don't work, we are either splitting hairs or don't have clear objectives. I think a clear consequence of this, is that humans should avoid introducing and we should often actively eliminate introductions. But, that idea is based on the premise that we want nature to run its course without human help - but that is not a universally accepted premise. And, a second premise is that evolution by natural selection and how nature may have influenced that through genetic drift, lateral gene transfer or what have you, is what is interesting about nature. I can see a future in which ecologists merely study how natural selection influenced organisms after their introduction, or as a consequence of the introduction of other species. Boring. After all, those will always be on a short term scale and will only illustrate what we probably already know about evolution. The big picture, long term consequence of continental drift, punctuated equilibrium and so on, which have resulted in the fascinating diversity of life, do not occur in one or two human generations - but we can certainly wipe out the evidence of them in the same short time frame. Extinctions and introduced species will do just that. Cheers, Jim
