This seems like a confusing answer. Let me put a more specific question. =
When there was a land bridge over the Bering Strait a lot of animals =
entered N. America from Asia. Does John's definition mean that a tick =
that arrived on a bear is native and one that arrived on a human is =
introduced?=20
Bill Silvert
----- Original Message -----=20
From: Dr. John Pipoly=20
To: William Silvert=20
Sent: Tuesday, May 02, 2006 5:21 PM
Subject: Re: Introduced Sp. Question
A species is native if it naturally occurs there, or was dispersed =
there, or if it is autochthonous. Introduced species means that the =
species was purposely or accidentally introduced by man.
These are semantics. The important thing is native vs. introduced and =
then whether the species is naturalized.
john pipoly
William Silvert <[EMAIL PROTECTED]> wrote:
This seems to imply that a species is native only if it evolves in =
the=20
location where it is found, and that any species which arrives by =
migration=20
or other form of transport is not native. This is a very Eulerian =
approach.=20
In particular, with global warming we can expect species to drift =
towards=20
the poles, so even though the entire ecosystem drifts polewards, can =
we say=20
that the component species cease to be native?
Bill Silvert
