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<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 type=cite class=cite 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>
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