This is an interesting discussion. However, comparing animals and plants in terms of extinction risk or reality is problematic. When an animal is extinct, there are very few questions. Gone is gone. With plants, it isn't so easy. With seeds lying dormant in the soil, a disturbance or a fire can stimulate their reemergence from "extinction". Just because it hasn't been seen for a decade does not mean it isn't extinct, but it doesn't always mean it is. This is one of the truly frustrating aspects for biological consultants who are asked to determine whether an endangered species is present on a plot of land. "I'm not sure" or "probably" are not acceptable answers. It might be present, but dormant. Similarly, declaring a plant extinct as a result of an invasion is a question that necessarily includes a huge temporal component, i.e., it will be when the seeds are all dead. But if even one seed remains (unlike animals), the species is still potentially "alive." Andy
Andrew R. Dyer Asst. Professor of Ecology Dept. of Biology & Geology University of South Carolina Aiken 471 University Parkway Aiken, SC 29801 Vox 803-641-3443 Fax 803-641-3251 [EMAIL PROTECTED] -----Original Message----- From: Ecological Society of America: grants, jobs, news [mailto:[EMAIL PROTECTED] On Behalf Of Teresa Woods Sent: Tuesday, April 04, 2006 2:49 PM To: [email protected] Subject: invasive plants A couple articles to consider: Gurevitch, J. and D.K. Padilla. 2004. Are invasive species a major cause of extinctions? TREE 19:470-474. Davis, M. 2003. Biotic globalization: does competition from introduced species threaten biodiversity? BioScience 53:481-489. I couldn't believe the conclusions of these articles when I read them last year, but they did bring home the message that if indeed invasives are causing extinctions, even community level ones, we need to be documenting them in ways other than anecdotally. Hence, my question about relevant publications. I'd love to see them. As I said, even ones that show a correlation, as causation is justifiably hard to show. I am not as familiar with aquatic invasives except to know that some like zebra mussels are extremely aggressive and destructive. But regarding plants, invasives are often linked with disturbed habitats, and it may be that habitat destruction is the primary cause of local extinctions, and the invasives follow as the "final nail in the coffin (Gurevitch and Padilla 2002)." It is also likely that the extinction trajectories are definitely occuring but are longer-term, and just haven't reached the end yet. The link to the NYTimes article was, as I said, meant to fan the flames here -- not that I agree in any way with him, but to put on the table what landscape designers and architects are surely also being influenced by -- even if from, as has been correctly pointed out, a very biased point of view. So my query still stands -- is there empirical evidence supporting the sense that most of us have that invasives are causing native extinctions? I'd love to have evidence to contradict the NYTimes author's view. Teresa Teresa Woods Graduate Assistant Division of Biology 232 Ackert Hall Kansas State University Manhattan, KS 66506 785-532-9834 [EMAIL PROTECTED]
