Well, that was interesting. Comments on a few highlights: - The “hand in glove’ analogy for species in environments is archaic and teleological. Assorted appendages in a bucket is probably a better analogy, but still useless for practical purposes. - I haven’t seen an attempt to sort out introduced and native agricultural weeds, but the question is effectively a non-sequitur. Regardless of geography, very few plant taxa could be considered native to agricultural operations unless we expand the usual criteria of nativeness. That expansion would open nativeness to both introduced crops and introduced “weeds” typical of various cropping systems (Alphonse De Candolle worked that out in 1855). But native and alien can’t do the work asked of them, either. There is no objective standard of ecological or biogeographical belonging beyond expressed evolutionary fitness. Sense of place is not universal among humans, much less across taxa. Most organisms don’t know they ‘are here’ and they certainly can’t conceive of being anywhere else at any other time. - Quantifying invasiveness has been attempted, and it comes across as fundamentally arbitrary (and a bit silly). It is not clear to me that we need the metaphors of invasion and invasiveness at all in order to make sense of introduced species. I think they obscure more than they reveal, which is what recommends this exercise. - It isn’t necessary to acknowledge native invasives because all that does is reduce taxa to membership in a foursquare classification (native noninvasive, native invasive, alien invasive, alien noninvasive). But that classification changes for every set of coordinates in the biosphere and every timeline point for each coordinate set. It is perfectly subjective. - If we agree to call humans megadispersers that still tells us nothing about dispersed taxa other than that they were prone to dispersal via human agency under some set of conditions. It certainly doesn’t move us away from being megadispersers. Should it? - Were we not all invaders? No, I don’t think we all were. It’s a mistake to lump dispersal with invasion. Doing so evidences a sort of intellectual entropy. - Are there meaningful difference between an organism that evolved with[in] an ecosystem and one that evolved outside it? Yes (drop a kangaroo into the middle of Lake Michigan and watch) but the difference is not meaningfully generalizable much beyond the obvious. I find it curious, for instance, that we acknowledge the similarity of ‘Mediterranean’ ecosystems on several continents but complain when other organisms confirm our judgments by occupying more than one. Even then each case is different, and we have been quick to overgeneralize with hopelessly broad categories.
Matthew K Chew Assistant Research Professor Arizona State University School of Life Sciences ASU Center for Biology & Society PO Box 873301 Tempe, AZ 85287-3301 USA Tel 480.965.8422 Fax 480.965.8330 mc...@asu.edu or anek...@gmail.com http://cbs.asu.edu/people/profiles/chew.php http://asu.academia.edu/MattChew
