My perception, please correct me if I have mistated anything! =20 Introduced species are those that have been established by humans. Invasive species are those that have the tendency to aggressively = dominate an ecosystem and crowd out other species.=20 =20 an introduced invasive is alien and aggressive (chestnut blight, = starlings, fire ants and red ear turtles would qualify!). a native invasive can occur as well (some maples and sweet gum come to = mind) their are also non-native invasives (cattle egrets might qualify as = this) that were not introduced by man, but introduced themselves! In = fact, man would be a non-native invasive in many parts of the world! =20 however, introductions need not be invasive alligator snapping turtles = were introduced in california in at least a couple of ponds. They = eventually died out. Some sustain but only on a very small scale. =20 =20 Where would nightcrawlers fall in this scheme? I'm not sure about their = biology! :) =20 =20 =20 =20 Malcolm L. McCallum Assistant Professor Department of Biological Sciences Texas A&M University Texarkana 2600 Robison Rd. Texarkana, TX 75501 O: 1-903-233-3134 H: 1-903-791-3843 Homepage: https://www.eagle.tamut.edu/faculty/mmccallum/index.html =20
________________________________ From: Ecological Society of America: grants, jobs, news on behalf of = Scott Ruhren Sent: Fri 4/7/2006 9:10 AM To: [email protected] Subject: Re: Biology of Invasion Dear Ecolog readers, This could open a can of worms but... how do list members define or = describe "aggressive colonizers" such as Smilax rotundifolia. This vine or = shrub-like species forms dense, impenetrable patches particularly in disturbed = suburban forests with a lot of sun? Though a native, much of this species' = behavior is "invasive-like." In "Weed Ecology in Natural and Agricultural = Systems" (2003), Booth, Murphy and Swanton suggest (my interpretation) that "invasive" may occasionally be applied to a native increasing in = population size and effect. I realize this is not popular but "weed," "invader" and "colonizer" still are used in often-conflicting manners. Scott --- Scott Ruhren, Ph.D. Senior Director of Conservation Programs Audubon Society of Rhode Island 12 Sanderson Road Smithfield, RI 02917-2600 401-949-5454 -----Original Message----- From: Ecological Society of America: grants, jobs, news [mailto:[EMAIL PROTECTED] Behalf Of Gary Ervin Sent: Wednesday, April 05, 2006 11:28 PM To: [email protected] Subject: Re: Biology of Invasion 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
