[APWG] Plants Alien Definition

[Randall, John L]

Greetings:  I'm sorry to have come in to this discussion at this late point, but what's wrong with the definitions used in the Executive Order on Invasive Species (13112), which I think are completely clear and accurate (http://www.invasivespeciesinfo.gov/laws/execorder.shtml).  Johnny Randall

From: apwg-bounces at lists.plantconservation.org [mailto:apwg-bounces at lists.plantconservation.org] On Behalf Of John Barr
Sent: Monday, August 02, 2010 12:34 PM
To: Bill Stringer
Cc: apwg at lists.plantconservation.org
Subject: Re: [APWG] Plants Alien Definition

Wayne,

Your definition for Alien appears to be workable.

Your definition for Invasive is, in my opinion, uselessly broad.  Using this definition, please name an organism that is not invasive?   All organisms attempt to "exploit niches that meet requirement for life", otherwise they die.

Adding to what Bill said, alien invasive species can be problematic not only because they have "very effective fitness traits", but because they can arrive without their coevolved biologic controls.  Citing one local example, fire ants arrived without phorid flies.   The non native fire ants are not necessarily more fit than native fire ant species.  The natives are held in check by coevloved controls.  http://www.sbs.utexas.edu/fireant/Research%20Program.html  Given enough time (and damage to native ecosystems) some controls for the fire ant will be expected to evolve locally.    (For the record, introducing one species to control another is something that I greatly fear.  The track record for these introductions is extremely poor.  In my opinion, much harm has been done.)

Native invasives on the other hand would much more likely arrive with their coevolved natural controls.  Using Robert Layton Beyfuss's example of native plants expanding up hillsides with climate change, the coevolved natural controls would be expected to move with the native invaders.  An entire ecosystem would likely move upslope.  This does not change the likelihood that the higher elevation species will be displaced, possibly to extinction, but we would not likely see the monocultures that the most problematic alien invaders are capable of producing.

So, we need to narrow the definition of invasive. This is guaranteed to ruffle feathers.  I

n my opinion, the concepts of "alien" and "invasive" are creations of people and not creations of nature.  I believe that most of us would not consider the species that arrived on the Galapagos islands before man to be alien invaders, but certainly we would consider those species man brought to the islands to be alien invaders.

As a second pass, I would propose: An alien invasive species is one that arrives in a new ecosystem, as a result of human intervention, to the detriment of the native ecosystem.  An alien invader can benefit one or more native species, but it must be understood in the context of the entire ecosystem.

By my definition, brown tree snakes on pacific islands invade with the direct intervention of humans (planes and boats), the native ecosystems climbing elevation as a result of human caused climate change is an indirect intervention, but an alien invasion none-the less.  If the climate change is not human caused, they are not alien invaders.  Our beloved armadillos in Texas are not alien invaders because they, apparently, arrived without human intervention.

Yikes,

John

On Aug 2, 2010, at 8:47 AM, Bill Stringer wrote:


Wayne, all organisms exploit niches that meet their life requirements.

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.

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.

Ramble, ramble..........

Bill Stringer

At 05:35 PM 7/30/2010, Wayne Tyson wrote:

APWG:

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.

1. Alien (plant or other organism). An organism that did not evolve with other organisms in a given habitat.

2. Invasive (plant or other organism). An organism that exploits niches that meet its requirements for life.


Relevant comments:

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.

2. Environmental change is the rule, and there are no exceptions. Change may be very fast or very slow, but nothing stays the same.

3. Organisms "track" changes within their sphere of influence/capacity.

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.

I look forward to alternative definitions and supportive reasoning and discussion.

WT

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