Re: NANFA-L-- Old story, new twist? Old twist new story

dlmcneely-in-lunet.edu
Thu, 18 May 2006 12:34:21 -0500

Hmmmmmmmmmm . Regarding the Amazon being formerly connected to
Africa: Well, not exactly. S. America and Africa were part of the
Gondwanan supercontinent, along with India, Madagascar, Australia, and
Antarctica. That continent broke up a couple of hundred million years
(forgive my impreciseness, I would need to look it up to get it exactly
right, and it might have been more than that number of years for that
matter) before the Amazon formed as the drainageway of the growing
Andean cordillera some 70 million years ago. The Amazon basin and
Africa do share a faunal history, however, and the fish families on
both continents are much more nearly related than those of N. America
and Eurasia north of the Himalaya are to either.

But the question is richness, not relatedness of fauna. The
Neotropical Realm is biotically diverse because it is old, not because
it has the particular families it has. Same for the Ethiopean Realm
(most of Africa). The Mississippi basin is quite rich for its
latitude, and the lack of glaciation in its lower reaches does account
for part of that. Almost all of Europe and most of Asia north of the
Himalaya were glaciated in the Pleistocene, only a few tens of
thousands of years ago, hence their fewer species than in the
Mississippi.

The difference between the Amazon basin and the Mississippi basin in
terms of species richness is a part of the great global pattern of high
tropical richness with declining richness northward and southward in
almost all taxonomic groups. That does not mean that the higher
latitudes are worth less or that their faunae should be threatened by
introductions of exotics. It means they are different from the
tropics, but valuable in their own right.

The bizarre suggestion of introducing-in-risk species from other
systems into the Mississippi because of its supposed lack of species
richness could, if carried to a further degree, involve introducing
eastern N.A.-in-risk species to the "depauperate" Pacific slope rivers
to save the species and enrich the Pacific slope rivers.

Get it ........... ?

Dave Mc

David L. McNeely, Ph.D., Professor of Biology
Langston University; P.O. Box 1500
Langston, OK 73050; email: dlmcneely-in-lunet.edu
telephone: (405) 466-6025; fax: 405) 466-3307
home page http://www.lunet.edu/mcneely/index.htm

"Where are we going?" "I don't know, are we there yet?"

----- Original Message -----
From: Moontanman-in-aol.com
Date: Thursday, May 18, 2006 10:09 am
Subject: Re: NANFA-L-- Old story, new twist? Old twist new story
> In a message dated 5/15/2006 3:59:40 PM Eastern Daylight Time,
> ichthos-in-comcast.net writes:
>
>
> So? Who cares that it has fewer species than tropical ecosystems?
> An
> ecosystem has just as many species as it can support. Compared to
> other temperate
> freshwater systems, the Mississippi Basin is the most diverse in
> the world. Its
> species are unique. When glaciers covered the northern part of
> the
> continent, it was the mighty Mississippi that served as a
> refugium and major center of
> fish evolution. Indeed, the Mississippi is the "mother" of North
> American
> fish diversity.
>
>
>
>
> I think i will have to disagree, glaciers had a very limiting
> effect on the
> fish diversity in the Mississippi. yes, eventually in millions of
> years you
> might get something approaching the number of niches occupied in
> the
> Mississippi that you have in the amazon but you have to remember
> the
> Amazon was-in-one time connected with Africa and so had a bigger
> pool of
> both diversity and disparity to draw from than the Mississippi
> will ever have.
>
>
> Michael Hissom
> aurea mediocritas
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