Wayne: Clements actually introduced the term "invasion" in his writings on succession. He even at some points more or less suggested that "succession" is a series of "successful invasions," as I indicate to my Plant Ecology students. However, I broached this very general concept of invasion on an "Invasive Species" list a couple of years ago, and it was not well received. I think the best recent effort at "standardizing" definitions is: Richardson, D. M., et al. 2000. Naturalization and invasion of alien plants: concepts and definitions. Diversity and Distributions 6:93-107. They present these as terms for use in Invasion Ecology, with accompanying definitions (better explained in the paper): Alien species - species that have overcome geographic barriers (i.e., non-native to the particular area of concern) Casual species - alien species that have overcome local environmental barriers in their new range Naturalized species - alien species that have overcome local environmental and reproductive barriers in their new range Invasive species - alien species that have overcome environmental, reproductive, and dispersal barriers in their new range, thus that they now readily spread and establish into either disturbed or undisturbed habitats Context is very important for individual species to realize their "invasive potential," as we all know that every species has some range of environmental tolerances - even invaders must fit their new habitats in order to invade. I'm sure list members could go on for days with specific examples of species that are highly invasive in some new regions and not in others. One great example is the Asian grass Arundo donax, which has caused relatively little concern here in the southeastern US but appears to be a huge problem in riparian areas of California. Gary ~~~~~~~~~~~~~~~~~~~~~~~~~~ Gary N Ervin, Asst. Prof Biological Sciences PO Box GY Mississippi State, MS 39762 USA on the web at: http://www.msstate.edu/courses/ge14/ for parcel delivery: Biological Sciences 130 Harned Biology, Lee Blvd Miss State, MS 39762 Tel.: (662) 325-1203 lab : (662) 325-7937 FAX : (662) 325-7939 ~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> Wayne Tyson <[EMAIL PROTECTED]> 04/05/06 5:23 PM >>> What is the definition of "invasion?" "Invasive species?" "Non-invasive alien species?" Are some (or all?) species invasive in some contexts but not others? Is "everybody" pretty much in agreement on such definitions or is there significant disagreement? WT
