Apparently I responded too quickly without choosing my words carefully enough. I do believe that by saying that a species evolves in response to the environmental factors within an ecosystem, I allowed for migration of an ecosystem or parts of an ecosystem in response to stresses such as global climate change. Also by saying that species introduced by man cannot become native I believe that I allowed for other types of migration.
Bob Mowbray -------------- Original message from William Silvert <[EMAIL PROTECTED]>: -------------- > This seems to imply that a species is native only if it evolves in the > location where it is found, and that any species which arrives by migration > or other form of transport is not native. This is a very Eulerian approach. > In particular, with global warming we can expect species to drift towards > the poles, so even though the entire ecosystem drifts polewards, can we say > that the component species cease to be native? > > Bill Silvert > Habitat Ecologist
