Greetings~ I am working on a predictive model at the Chicago Botanic Garden and am often trying to decode the way we communicate about this topic. At least three different paradigms address non-native and non-native invasive plants. As a general assessment, I have seen, "weedy", a horticultural and/or agricultural term (IMO), superimposed on "invasive", a ecological term (IMO) and "noxious", a legal term (in Illinois, anyway) used synonymously, as well. While I see that invasive can be a subjective term, as scientists, we can define the term (as this is fast becoming the standard in publications) to minimize much subjectivitity, and indeed, we have a plethora of literature that attempts to do this. Some address not only the "invasive" term, but all terms involved in invasion ecology as well as the process itself. Among others, I find this 1999 attempt to be one of the most specific. Based loosely on Parker, IM, D. Simberloff, WM Lonsdale, K. Goodell, M. Wonham, PM Kareiva, MH Willilamson, B. Von Holle, PB Moyle, JE Byers & L. Goldwasser. 1999. “Impact: toward a framework for understanding ecological effects of invaders”. Biological Invasions 1: 3-19. Invasive Species a species, usually non-native, that has a quantitative and statistically significant direct or indirect adverse biological impact on native flora or fauna or abiotic input where impact is based on total area occupied, abundance and some measure of the impact per individual species and/or abiotic unit. Further, Richardson, Pysek, Rejmanek, Barbour, Panetta and West (2000) say "invasion further requires that introduced plants produce reproductive offspring in areas distant from sites of introduction (appx scales: > 100m over < 50 years for taxa spreading by seeds and other propagules; > 6m/3 years for taxa spreading by roots, rhizomes, stolons or creeping stems)." And the IUCN definition for "Alien Invasive species" "means an alien species which becomes established in natural or semi-natural ecosystems or habitat, is an agent of change, and threatens native biological diversity." (Feb. 2002). The never-ending discussion.... As a side note, regarding the Daehler and Thompson and Davis papers noted by Teresa; Rejmanek, M., Richardson, DM, Barbour, MG, Crawley, MJ, Hrusa, GF, Moyle, PB, Randall, JM, Simberloff, D., and Willilamson, M. in the April 2002 Bulletin of the Ecological Society of America say of the Thompson and Davis paper, "We believe that the definition of invasive by Davis and Thompson (2001) would be more hindrance than help to conservation." The commentary by the above authors is entitled "Biological Invasions: Politics and the Discontinuity of Ecological Terminology". KEK Teresa Woods <[EMAIL PROTECTED]> wrote: A couple more relevant references on the definition theme:
Daehler, C.C. 2000. Two ways to be an invader, but one is more suitable for ecology. Bulletin of the Ecological Society of America 82:1101-102. Davis, M.A. & K. Thompson. 2000. Eight ways to be a colonizer; two ways to be an invader: a proposed nomenclature scheme for invasive ecology. Bulletin of the Ecological Society of America 81:226-230. Teresa Teresa Woods Graduate Assistant Division of Biology 232 Ackert Hall Kansas State University Manhattan, KS 66506 785-532-9834 [EMAIL PROTECTED] --------------------------------- Talk is cheap. Use Yahoo! Messenger to make PC-to-Phone calls. Great rates starting at 1¢/min.