Invasive versus Adaptive   Dean Hedin
  Jun 02, 2006 01:51 PDT 

Escaped? You make it sound like it's a Mexican illegal crossing the border!

You say "invasive species", However one might say "adaptive species".
I was wondering where is the line drawn?

There are some invasive species that I do get angry over, but I don't feel
this way about Robinia.   In fact, I have a serious respect for Robinia

Robinia pseudoacacia seems to grow quite well outside of it's natural range
(reported to be Appalachian Mountains from Pennsylvania to Alabama). Indeed
it has been planted (by man) the world over. It's been planted in Israel,
China, Indonesia, Hungary, Canada, etc..

However, if we imagine for a moment that mankind never existed, who is to say
that Robinia pseudoacacia would not have spread to new ranges on it's own?

The reason I say this is that Robinia pseudoacacia produces an abundance of
protein rich seed. It's not hard to imagine that a bird could eat a seed,
migrate a few hundred miles, and start a new stand of Robinia trees well
outside it's natural range. If it is adaptable to this new environment it
will proliferate (which seems to be the case).

What I am trying to say is we have no idea how fast Robinia pseudoacacia's
natural range was expanding before man discovered it. For all we know, it
may have been expanding like wildfire.

Recent phylogeny studies indicate that tribe Robinia has it's early origins in
the Greater Antilles (Lavin).

So what we have is a tree species of tropical origin that has begun to adapt
to temperate climates. More importantly, this species is nitrogen fixing.

There are many nitrogen fixing trees in the tropics. In fact, it is a paradox
as to why there are so many. Many of them have been quite successful . For
example, a distant relative of Robinia is Dalbergia (the Rosewoods).     

Examples of the Dalbergia species can be found throughout the tropical belt
around the world.   Was anybody screaming "Invasive" when African Blackwood
(Dalbergia melanoxylon) begat Boise de Rose (Dalbergia maritima, Madagascar)
begat Indian Rosewood (Dalgergia latifolia) begat Cocobolo (Dalbergia Retusa,
Costa Rica) begat Kingwood (Dalbergia cearensis, Brazil)?   There are many
more...

Each member of Dalbergia has the same chromosome number and in many cases it
takes an expert to be able to distinguish individual species morphologically.
This would indicate that the diversification of tribe was recent and it
somehow was quickly dispersed around the globe.   How do you think that
happened? I wonder if there was a loss of diversity in the native fauna when
Dalbergia came along and took hold in a new place.

But it is unusual for one of these trees to evolve to temperate regions.   
So, as far as trees go, this is a pretty grand evolutionary step for Robinia,
wouldn't you say?

So I ask where is the line drawn between "invasive" and "evolution in
progress"?

Granted, man has made some mistakes that have caused great harm to native
species, but at the same time there are aspects of ongoing evolution that are
inescapable.
RE: Invasive Plants (Coast to Coast)   Robert Leverett
  Jun 02, 2006 04:44 PDT 

Dean,

   Great post. Lots of good information. Incidently, I'm with you on
Robinia. I love the species. It has started to bloom here in the
Connecticut River Valley. Fragrance is its hallmark. I think I'll have a
special T shirt made up saying "I'm Bullish on Robinia".

   When Monica, Holly, and I were at the Pine Plains sycamore on Sunday,
a short distance up the road there are some positively huge black
locusts. They are in yards, but the are huge. The species does
exceedingly well in western Massachusetts and central New York.

   The questions you raise about invasive versus adaptive are
intriguing. I hope others will pick up on this one. It merits further
discussing.

Bob
Re: Invasive versus Adaptive   Don Bertolette
  Jun 02, 2006 16:11 PDT 

Dean-
I suppose it's all a matter of context...as one who has the responsibility
of managing 'alien invaders' in Grand Canyon National Park, it is a serious
challenge to eradicate those exotic species that outcompete the native
species, effectively altering the vegetatative community. Mandated to
'preserve and protect', we know where our line is drawn.
In another context, all plants are opportunists and will 'invade' any
environment that they can. They utilize wind currents, overland waterflow,
animal fur, bird and animal digestive tracts as vectors to new
environments...I think that the point where automobiles and heavy equipment,
or even the innocuous hiker/backpacker who doesn't take the time to clean
the mud out of his boots, become the vector, that's the point we need to
reconsider our role as not a natural vector.
Regarding Robinia, we like our Robinia neomexicana (New Mexican Locust) out
here too!
-DonB
Re: Invasive Plants (Coast to Coast)   Dean Hedin
  Jun 02, 2006 21:09 PDT 

On Friday 02 June 2006 10:26 am, Don Bertolette wrote:
  Dean-
..I think that the point where automobiles and heavy
equipment, or even the innocuous hiker/backpacker who doesn't take the time
to clean the mud out of his boots, become the vector, that's the point we
need to reconsider our role as not a natural vector.
Regarding Robinia, we like our Robinia neomexicana (New Mexican Locust) out
here too!
-DonB

So the line is drawn where man is the "unnatural vector".

I am not convinced that is a clear line drawn.   It's like saying "I can't
hurt the environment if I don't interact with it".   But I agree we should
make every effort to exercise the precautions you mention.

If I go into a area outside Robinia's natural range, an area where soil is
poor and erosion is a problem. I then decide to plant some Robinia and it
flourishes. A few years or decades go by, and now a small forest takes hold.
Some of the Robinia has spread outward but the original stand has faded. Now
there are some native species taking hold in the enriched soil etc..

Have I done something wrong here?
Re: Invasive Plants (Coast to Coast)   Don Bertolette
  Jun 03, 2006 22:51 PDT 

Dean-

I'll probably get in trouble here with somebody, but here goes...the Grand
Canyon is relatively undisturbed in the context of the duration of
occupation found in much of the North and South East (GSMNP excluded of
course!, and I know that there are notable exceptions here and there)...so
we're trying to run a "tighter ship"...I am not exactly sure of your
location, but my guess is that there have been several successive waves of
occupation over the last several centuries...your planting some Robinia that
flourishes is a much more miniscule "infraction"...
You're absolutely right, the line is not clearly drawn, and it's not a
straight one for every location...but it's a good one to question~~~~~

-DonB