Honorable Forum:
Frankly, y'all, Nature doesn't give a damn, but if we are the intelligent
species we claim to be, we can readily see effects and sometimes causes--at
least partially. What ecology is all about is finding things out, including
finding out that what we found out wasn't what we thought it was . . .
Evolution is largely about isolation, even though all other aspects of
habitat/environment are about equal, no?
Homo sapiens is a "mega-disperser" if there ever was one, and this includes
species which otherwise wouldn't have had a prayer of invading habitats
otherwise barred to colonization, such as those, the propagules of which
could not otherwise survive the journey or, once arrived, would not become a
dominant element or survive at all as "recruits" in the absence of
accompanying anthropogenic effects (e.g. cultivation, introduction of
domestic animals and their associated organisms).
Ecosystems are not tied to geography, they are tied to the ever-changing sum
of conditions to which the "constituent" organisms are continuously adapting
or failing to adapt. Their geography is incidental.
If one takes an organism out of its "natal" ecosystem in a
geographically-defined sense and deposits it in another
geographically-defined one, one can observe that the organism either
"succeeds" or "fails." Different organisms and associations that evolved in
different geographic regions under otherwise very similar conditions will
share an approximately comparable suite of requirements (most prominently
climate, as in Mediterranean ecosystems, for example) that increase the
likelihood of "success" in a geographically distant environment under which
the invading/introduced/dispersed species did not evolve. Species like "crop
weeds" from the Mediterranean region may (and many have) be wildly
successful in, say, parts of SW Australia, parts of Chile, and parts of
California and Mexico, where the climate is so similar. Such organisms may
prove adapted to any or all of those geographic regions, or have sufficient
potential to so adapt. But the crop weeds in particular may also be adapted
to cultivation or other perturbations, such as the trampling and scuffling
of accompanying "domestic" animals, and some may be dependent upon such
continuing perturbations for their continued existence, especially as
dominant features of the "adopted" ecosystem.
WT
"Correlation is not causation." --Original author obscure
----- Original Message -----
From: "Mitch Cruzan" <[email protected]>
To: <[email protected]>
Sent: Sunday, September 11, 2011 9:59 AM
Subject: Re: [ECOLOG-L] a non Ivory Tower view of invasive species
No organism is currently present only within the ecosystem it originally
evolved in - including humans. That's what successful species do - they
expand their ranges. Current distributions probably have more to do
with historical contingencies - dispersal, random chance, etc. I think
Gleason and Whittaker did a fairly good job of arguing against such
Clementsian views of community structure; biotic interactions matter -
yes - but probably only to a small degree compared to abiotic factors.
It's also notable that the large majority of 'alien' species have
evolved do some degree in their invaded range - does that make them
'evolved in their current ecosystems?' It is extremely difficult to
develop a scientific rationale for what we consider 'alien' vs.
'native.' What about the South Florida tropical flora/fauna? Many
species in those systems only arrived on this continent only within the
last 5000 years - are they invasive? Are entire communities in the
everglades invasive?
On 9/11/2011 8:18 AM, Wayne Tyson wrote:
Warren and Ecolog:
Naw, Warren, you're making a valid point that sums up the situation quite
succinctly. I hope this will lead to the expression of more such simple
elegance.
I would add only that organisms and their habitats, both in a constant
state of change, fit together like a hand and a glove.
However, this means neither that all aliens must be extirpated, nor that
all will be well if nothing is done in every case where the vastly
accelerated and facilitated dispersal of organisms 'round the globe by
that species we call Homo sap. Of course, Nature will ultimately bat last,
and of course, much weed-bashing is anthropocentric. But the President's
letter absolving humans and their introductions from the definition of
"alien" should be contested by all scientists, ecologists, and thinking
individuals and their organizations worthy of their designations.
WT
----- Original Message ----- From: "Warren W. Aney" <[email protected]>
To: <[email protected]>
Sent: Saturday, September 10, 2011 6:20 PM
Subject: Re: [ECOLOG-L] a non Ivory Tower view of invasive species
There can be a meaningful ecological difference between an organism that
evolved with an ecosystem and an organism that evolved outside of but
spread, migrated or was otherwise introduced into that ecosystem. An
organism that evolved with an ecosystem is considered a component that
characterizes that ecosystem. An introduced organism that did not evolve
with that ecosystem should at least be evaluated for its potential
modifying
effects on that ecosystem.
Am I being too simplistic?
Warren W. Aney
Senior Wildlife Ecologist
Tigard, OR
-----Original Message-----
From: Ecological Society of America: grants, jobs, news
[mailto:[email protected]] On Behalf Of Manuel Spínola
Sent: Saturday, 10 September, 2011 12:22
To: [email protected]
Subject: Re: [ECOLOG-L] a non Ivory Tower view of invasive species
With all due respect, are not we all invaders at some point in time?
Best,
Manuel Spínola
2011/9/10 David L. McNeely <[email protected]>
---- Matt Chew <[email protected]> wrote:
> We can compose effectively endless lists of cases where human
agency has
> redistributed biota and thereby affected pre-existing populations,
> ecological relationships and traditional or potential economic
> opportunities. Those are indisputable facts.
The House Sparrow is in North America by human hand.
> But what those facts mean is disputable.
House sparrows are in serious decline in Europe, probably as an
unintended
consequence due to human actions.
>
> I see effects; they see impacts.
> I see change; they see damage.
Many people see a need to eradicate non-natives. At the same time, many
people see a need to preserve natives.
With regard to the house sparrow ------ hmmm......... .
Where does the "arms race" that Matt mentioned further along in his post
lead?
mcneely
>
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