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<DIV><FONT face=Arial size=2>Quite. Note that I took care not to claim that
"other" organisms did not exploit niches that meet their life requirements; all
organisms are opportunists. Indigenous plants are, by definition, matched in
their life requirements with the conditions under which they have developed
adaptations (these niches are not always broad regions, but niche layers within
them). Healthy ecosystems tend to resist invasion. Invasions may require
"disturbances" to reproduce and persist. Just killing invaders, while satisfying
to the practitioner, is not likely to prevent reinvasions unless the disturbed
conditions which tipped the balance toward invasion also are corrected. One test
of a true ecosystem restoration is its resistance to invasion. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>WT</FONT></DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=bstrngr@clemson.edu href="mailto:bstrngr@clemson.edu">Bill
Stringer</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=landrest@cox.net
href="mailto:landrest@cox.net">Wayne Tyson</A> ; <A
title=apwg@lists.plantconservation.org
href="mailto:apwg@lists.plantconservation.org">apwg@lists.plantconservation.org</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, August 02, 2010 6:47
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [APWG] Plants Alien
Definition</DIV>
<DIV><BR></DIV><FONT size=3>Wayne, all organisms exploit niches that meet
their life requirements. <BR><BR>Invasive organisms invade, ie. they
move in and aggressively displace indigenous organisms and communities, thus
decreasing the species diversity. They are successful because they have
1 or more very effective fitness traits that allow them to exploit a wide
range of niche conditions, and deny/ reduce resource availability for
indigenous plants.<BR><BR>Indigenous plants, because they have evolved in an
ecosystem to be compatible with many other species in that ecosystem, are not
by nature aggressive exploiters of resources in that "home"
ecosystem.<BR><BR>Ramble, ramble..........<BR><BR>Bill Stringer<BR><BR>At
05:35 PM 7/30/2010, Wayne Tyson wrote:<BR></FONT>
<BLOCKQUOTE class=cite cite="" type="cite"><FONT size=2>APWG:
<BR></FONT><FONT size=3> <BR></FONT><FONT size=2>Definitions, to be
useful in moving a discussion forward as opposed to spinning its wheels in
polarizing dialectics, must be understood equally well and agreed upon by
all participants. While it would seem unnecessary to engage in such a
discussion with respect to "alien" and "invasive," I find that different
posts seem to define these key terms differently. Therefore, I will propose
some definitions (particularly as they relate to plants, but they should
hold true for any organism). I ask that responses be confined to corrections
to the definitions in the form of alternative definitions to keep the
discussion from wandering off into the intellectual weeds. Separate footnote
discussions about the reasoning that supports the definitions will be
welcome, of course, but I respectfully request that we keep it simple and
stick to the subject. It is not my intention to preserve these definitions,
nor to start arguments; my hope is that definitions will evolve that will
serve to communicate these concepts clearly. If no unanimity can be found or
resolved, clarity in communication can still be served by using modifiers to
define the kind of "alien" or "invasive" is intended. Anyone can define
anything any way one wants, but only one person may understand that
definition in the same way as the originator. <BR></FONT><FONT
size=3> <BR></FONT><FONT size=2>1. <I>Alien</I> (plant or other
organism). An organism that did not evolve with other organisms in a given
habitat. <BR></FONT><FONT size=3> <BR></FONT><FONT size=2>2.
<I>Invasive</I> (plant or other organism). An organism that exploits niches
that meet its requirements for life. <BR></FONT><FONT
size=3> <BR> <BR></FONT><FONT size=2>Relevant
comments:<BR></FONT><FONT size=3> <BR></FONT><FONT size=2>1. All plants
and animals reconcile their requirements for life with environments that
meet them. Invasions may occur, but the invading organisms must "find" or
create environments that are suitable for their requirements in order to
establish and maintain populations that are able to reproduce.
<BR></FONT><FONT size=3> <BR></FONT><FONT size=2>2. Environmental
change is the rule, and there are no exceptions. Change may be very fast or
very slow, but nothing stays the same. <BR></FONT><FONT
size=3> <BR></FONT><FONT size=2>3. Organisms "track" changes within
their sphere of influence/capacity. <BR></FONT><FONT
size=3> <BR></FONT><FONT size=2>4. Analogously, human cultures acquire
places to live in which they exclude others (aliens). In that process, other
species exploit the effects of human cultural differences. Some species of
rats, for example, have become almost entirely dependent upon human cultures
for their existence and would be restricted to non-cultivated or undeveloped
habitats and might not survive, at least in large populations, outside the
boundaries of human cultures. Certain plants have become highly dependent
upon human cultures for their existence ("crops" and "weeds"), and may have
evolved as a result, perhaps to such an extent that they could not otherwise
exist (or could be highly restricted to certain habitats) in its absence.
<BR></FONT><FONT size=3> <BR></FONT><FONT size=2>I look forward to
alternative definitions and supportive reasoning and discussion.
<BR></FONT><FONT size=3> <BR></FONT><FONT size=2>WT<BR></FONT><FONT
size=3><BR>_______________________________________________<BR>PCA's Alien
Plant Working Group mailing list<BR>APWG@lists.plantconservation.org<BR><A
href="http://lists.plantconservation.org/mailman/listinfo/apwg_lists.plantconservation.org"
eudora="autourl">http://lists.plantconservation.org/mailman/listinfo/apwg_lists.plantconservation.org</A>
<BR><BR>Disclaimer<BR>Any requests, advice or opinions posted to this list
reflect ONLY the opinion of the individual posting the
message.</FONT></BLOCKQUOTE>
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