Although the paper below deals with plants, you may be able to glean concepts relevant to your system.
Richardson, D.M., P. Pysek, M. Rejmanek, M.G. Barbour, F.D. Panetta & C.J. West. 2000. Naturalization and invasion of alien plants: concepts and definitions. Diversity and Distributions 6:93-107. They address the many meanings of "invasive" and propose, based on a lit review, certain definitions. They also consider how far back we go for a species' introduction to not be considered alien or exotic. Best wishes, Teresa Teresa Woods Graduate Assistant Division of Biology 232 Ackert Hall Kansas State University Manhattan, KS 66506 785-532-9834 [EMAIL PROTECTED] Quoting Dave Thomson <[EMAIL PROTECTED]>: > Mr. Mowbray, > > I would disagree with your claim that "we" ecologists (smile) agree > that > early succession natives are "invasive species" in the sense of the > Ms. > Faber's question. I was out of town during that last discussion > (still > trying to find the time to go thru it and comment), but my knee-jerk > response to your statement is: lumping natives and exotics lumps > different issues together and would be a mistake. > > Ms. Faber, > > I have worked with the issue of invasive species often over the last > 5 > years in the field of restoration ecology. Obviously this is in the > applied sense, and much of the conceptual work preceded my own. But > I > have also had to accept, reject or adapt the concepts I have learned. > This has led me to develop an opinion on the subject... > > Of course what's needed is consensus, not more opinions; fortunately > there are examples of majority consensus. One I am familiar with: in > California State, the problematic species are called "noxious weeds". > That term traditionally relates to plants that invade agricultural > crops > but the definition has widened as the State learned that plants can > be > significant negative impacts in other sectors of the economy. You > can > get more info on that program here: > > http://www.cdfa.ca.gov/phpps/ipc/noxweedinfo/noxweedinfo_hp.htm > > And here are several definitions of "weeds": > http://www.blm.gov/ca/pa/weeds/weed_definitions.html > > It has been my experience that the term "invasive" is singularly > subjective, and I can appreciate many (but not all) of those, ah, let > me > just say it - value judgment. Just as you pointed out, "bad" is a > value > judgment; so too is "invasive". Therefore, you will have to > determine > what your criteria are for making that judgment, preferably a priori. > > In your pursuit of a working definition of "invasive" I suggest you > start by defining what is "native". The components of 'nativity' > will > guide your definition of what is not, and how that difference relates > to > the ecology of your system. And from that point you can look at an > exotic species' impacts and determine your value judgment of what is > "invasive". > > Components of nativity: the temporal component is important. Are you > going to rely upon historical accounts or work with the > paleoecologists > on what was present in, say, the pollen record. For example: > > http://links.jstor.org/sici?sici=0002-9122%28197811%2F12%2965%3A10%3C111 > 7%3ATOOCSV%3E2.0.CO%3B2-6&size=LARGE > > Your question, "does how long ago it was introduced matter?" is a > good > one. Perhaps rather than set a "naturalization" time period rule, > consider ranking other factors higher. If a species (or a direct > ancestor...) is known by paleobiologists to have occurred onsite > prior > to human influence then you are safe in assuming it is a native. If > not, then you may have to consider other factors in determining what > "matters". > > Other factors... there is a good group in my State that deals with > invasive plants: http://www.cal-ipc.org/ if you look at their > invasive > plant inventory it will state a short blurb for each category that I > think is very helpful. Sorry I am not much help with the other > Kingdoms > but perhaps these concepts will be applicable in yours or at least > wrap > your brain around the concepts? > > All that and I didn't even get to use my favorite label: > "Cosmopolitan > Species"... (eucalyptus trees in California) but it is Friday! I'd > be > happy to discuss this more if you wish. > > > David Thomson M.S. > Restoration Ecologist/Wetlands Scientist > Schaaf & Wheeler > 100 N. Winchester Blvd., Suite 200 > Santa Clara, CA 95050-6566 > (408) 246-4848 x119 > (408) 246-5624 (fax) > [EMAIL PROTECTED] > > > -----Original Message----- > From: Ecological Society of America: grants, jobs, news > [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] > Sent: Thursday, April 20, 2006 2:31 PM > To: [email protected] > Subject: Re: Definition of invasive species... > > Betty - > > We had a long discussion on this topic right here about a week or so > ago. The discussion went on for about 10 days. I assume that this > listserve has an archive which members can access. If so, you might > want to take a look at the archives for the month of April (perhaps > even > the last couple of days of March, but if you look at the first week > or > so of April that should tell you whether you need to expand your > search > on either end). The discussion started when someone asked for > suggestions for textbooks to use in teaching ecology to landscape > architecture students. > > I think that we agreed that an invasive does not have to be > introduced - > that many early successionary species are invasives. Invasive > exotics > are introduced, and, I don't think it should make any difference how > long ago they have been introduced although perhaps it shoujld be > limited to the time period during which man has had the capability to > spread invasive exotics to new environments. I would classify > domestic > animals which have the ability to escape and outcompete native plants > and animals as invasives - feral cats perhaps. Certainly goats in > places like the Galapagos. > > Bob Mowbray > Tropical Forest Ecologist > > > -----Original Message----- > From: Ecological Society of America: grants, jobs, news > [mailto:[EMAIL PROTECTED] On Behalf Of Betty Faber > Sent: Thursday, April 20, 2006 1:19 PM > To: [email protected] > Subject: Definition of invasive species... > > I am working up some programs on the Asian long-horned beetle and > more > general aspects of invasive organisms. > > >From a cursory glance at the internet, and various publications, > there > seems > to be many different definitions for "invasive species." > > Are there accepted views on this term? I would guess that an > invasive > is > always introduced but does "how long go it was introduced" matter? > Are > invasives always "bad" and does bad have real meaning? Are domestic > animals > that are not indigenous considered invasives? > > Thank you for any discussion. > > Betty Faber, PhD > Science Consultant > Liberty Science Center > >
