Re: [Aroid-l] Invasive plants

**&* B* <m*@botany.ufl.edu>**

Is Pistia "invasive"?
Ten years ago, there was still a dispute, whether Pistia originated in the
New World or in the Old World.  That is, nobody really knew, where it was
native to - and where "invasive".
Has there been new evidence published, showing that Pistia has not been
around in the warm climate of the New World since prehistoric times?  Please
provide new literature (after 1994) that shows Pistia was introduced (by
Europeans or other Old Worlders).
With "shows" I mean hard evidence. I am aware that several articles call
Pistia "invasive", especially to Florida.  But I never found evidence to
proof Pistia's absence prior to Europan arrival. Believing something is
"invasive" because everybody says so is not science, but mythology.
Note:
Does the community consider a plant "invasive" because it can temporarily
form monocultures?  Then, are Phragmites australis and Fagus silvatica
"invasive" in Europe?
Thanks
Matyas
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