Wayne, and others,
This email was nebulous enough to where it appears to me that several
concepts are being bantered around to the detriment of resolving any.
Of course all terms are relative - we humans made up language to put
names on things to help us.
The problem of invasive species is important or not, depending on your
particular philosophy, so you would have to come to some common grounds
first to resolve what invasive is second.
The problem of invasives is just like the problem of endangered species.
99% of all species that ever lived are extinct, so we know that it is a
consistent evolutionary process. Probably 99% of all species that exist
started out somewhere else. However, the glitch is that in our
generation, we are causing the extinction of many species at a much more
rapid rate than nature ever did, and we are causing the introduction of
species in new places at a rate much more rapid than nature ever did.
As Elton in his classic book on introduced species stated (here
paraphrased), Because of introductions and their consequences, we will
be left with a world much simpler, much less diverse, and much less
interesting.
Sincerely,
Jim
Wayne Tyson wrote on 07-May-10 16:47:
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
--
James J. Roper, Ph.D.
Ecologia, Evolução e Dinâmicas Populacionais
de Vertebrados Terrestres
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