Ecolog: Back on April 12, 2010, I posted an enquiry along these lines that resulted in an off-list discussion between three Ecolog-l subscribers and three others. A lot of interesting points were made, but this side discussion did not, in my view, settle the matter of what terminology, if any, should be used to describe the ecological phenomena associated with plants (and other organisms) that "colonize" or "invade" parts of the earth upon which they did not appear/evolve before dispersal by human culture (including various artifacts and impacts and domesticated plants and animals and their cohorts).
Since the off-line discussion did not seem to resolve the issue beyond opinions, I am submitting my version of the results for consideration by the Ecolog community. Among the points (you can ignore these, but they give SOME idea of where the discussion wandered) made by various correspondents were: 1. Persistence is an interesting problem, since it requires an arbitrary stipulation. Fitness is demonstrated (or not) generation by generation. 2. . . .why ARE so-called "natives" of a higher value than so-called "exotics"? How far back are we supposed to go before something is considered "native?" 3. . . . humans should learn how the land works, make minimal changes and only necessary ones, and try to adapt to the landscape as best as possible, using history's lessons to create our future. Trying to make zero "footprint" or impact or change as we live our lives is like trying to swim without getting wet or making ripples. 4. Eventually Albert Thellung split 'aliens' into 7 distinct categories in 1912: ergasiophytes, ergasiolipophytes, ergasiophygophytes, archaeophytes, neophytes, epecophytes, and ephemerophytes; plus two more denoting 'wild' plants growing in modified habitats. Search any of them and they'll pop up in recent central European literature, but they're dead letters in the Anglophone world. 5. Alien and invasive are both relative. The labels are relevant only in areas where new populations have (respectively) appeared, and spread in some discomfiting manner. They provide no information about any biological essence of any species . . . 6. What matters is fitness under prevailing conditions. 7. . . . the whole question of what response to invasive species is morally best is beside the point. 8. For now, I still believe that each of these terms reflects an objective reality, but that each has nebulous boundaries. 9. The danger of separating natural from artificial mentally might be that we think we have to exclude nature wherever we go. The danger of not separating them is that it can help us rationalize an anything-goes approach to natural systems. 10. Have we decided on any definitions, or are there still differences about terminology? Are we ready to list them yet, even if with a multiplicity of definitions? Either way, it looks like we're making entertaining progress in the realm of associated phenomena. Maybe that's the first, if indirect, hurdle in gaining a workable set of terms? 11. My question is, what belongs there, and why? 12. . . . the important thing is to keep the lines of communication open--ESPECIALLY with those who have "alien" ideas. 13. Once an idea catches on, it's next to impossible to replace it with another one--something like the tenacity of an alien species--or, one might also say with equal "validity" or "spin," that, like the popular pastime of reasoning by analogy, that it is an example of resistance to invasion. 14. I am interested in the question of whether we ought to "subsidize the unfit, and suppress the fit." My own summary interpretation of some of the various conclusions are: 1. All organisms move from place to place by some means. 2. Some don't survive in some places. 3. Some survive and reproduce in "new" places better than some of the organisms that apparently evolved adaptations in accordance with site conditions. 4. Because of various semantic alliances, word meanings and etymology, and interpretations thereof, terms like "colonizer," "invader," and "alien" are deemed unsatisfatory to some for the purposes of disciplined enquiry into ecological phenomena. 5. Testable hypotheses seem to be lacking. This is all very incomplete; I hope that contributions from Ecolog subscribers will help to make it more so, if not resolve the issue(s). WT